WO2019015658A1

WO2019015658A1 - Color-tunable organic light emitting diode devices based on a single emitter and methods thereof

Info

Publication number: WO2019015658A1
Application number: PCT/CN2018/096349
Authority: WO
Inventors: Chi Ming Che; Mao Mao; Gang Cheng
Original assignee: The University Of Hong Kong
Priority date: 2017-07-19
Filing date: 2018-07-19
Publication date: 2019-01-24
Also published as: CN110945669A; CN110945669B

Abstract

Described herein are methods for using and making voltage-dependent color-tunable OLED devices using a single platinum emitter. The platinum emitter may be a Pt (II) complex. A single platinum emitter is mixed with host materials in an emissive layer of the OLED device. The emissive layer can comprise a single high concentration emitter, or can comprise two sub-layers in which one layer has a low emitter concentration to produce monomer emission and the other layer has a high emitter concentration to produce excimer emission. As voltage is applied to the OLED, the device emits different colors. Also disclosed herein are devices that comprise the platinum emitters and methods of making and using the platinum emitters.

Description

COLOR-TUNABLE ORGANIC LIGHT EMITTING DIODE DEVICES BASED ON A SINGLE EMITTER AND METHODS THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No. 62/534,417, filed July 19, 2018, which is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The disclosed invention is generally in the field of organic light emitting diodes (OLEDs) . More specifically, described herein are methods for using and making voltage-dependent color-tunable OLED devices using a single platinum emitter. Also disclosed herein are devices that comprise such platinum emitters.

BACKGROUND OF THE INVENTION

White light emitting materials have attracted enormous attention of its application in lighting and display. In particular, white light can be produced by organic light-emitting diodes ( “OLED” ) , which are solid state thin film devices composed of stacked organic layers sandwiched between two electrodes. Light is generated in the electroluminescent layer containing an emissive (e.g., a metal complex or polymer) . White light emission can be achieved by mixing three primary colors (i.e., red, green, and blue) or two complementary colors from different emitters disposed within the emissive layer, or by fabricating a device structure having multiple emissive layers or by fabricating two or more sub-OLEDs combined together.

However, the implementation of two or more emitters or three or more emissive layers, or two or more sub-OLEDs comes with many drawbacks. First, each additional OLED component or sub-component increases the complexity and cost of the OLED. Further, at typical luminance of OLED lighting (i.e., 1000-5000 cd/m ²) , such arrangements suffer from strong efficiency roll-off, lower external quantum efficiency ( “EQE” ) , high driving voltage and low color rendering index ( “CRI” ) values between 40-70 CRI (due to a narrow light emission band) . Current methods of color-tunable white light OLEDs are unable to reach maximum luminance over 20,000 cd/m ².

It is in regard to these issues and others that the present disclosure is provided.

BRIEF SUMMARY OF THE INVENTION

Disclosed are compounds, devices, and methods useful for voltage-tuned OLED devices. Disclosed are methods for voltage-tuning an OLED device, the method comprising: providing a first voltage to the OLED device to cause the OLED device to emit a first color with a first wavelength; and adjusting the first voltage to a second voltage to the device to cause the OLED device to emit a second color with a second wavelength. In some forms, the OLED device has a pair of electrodes having opposing polarity and a plurality of organic layers disposed between the pair of electrodes. In some forms, at least one of the plurality of organic layers is an emissive layer and the emissive layer includes a single emitter mixed with one or more host materials. In some forms, the emitter is an organic luminescent material or a metal complex that emits fluorescence or phosphorescence and the emitter has both monomer-state emission and aggregation-state emission. In some forms, the first voltage and the second voltage have a difference of 1V. In some forms, the first voltage is 2.4V or greater.

Also disclosed are methods for making a voltage-tunable OLED device, the method comprising: obtaining an emitter wherein the emitter is organic luminescent material or metal complex, which can emit fluorescence or phosphorescence, and has both monomer-state emission and aggregation-state emission; and mixing the emitter with one or more host materials to fabricate the emissive layer. In some forms, the percentage by weight of the emitter of the emissive layer is 2-30%. In some forms, the OLED devise has a pair of electrodes having opposing polarity and a plurality of organic layers disposed between the pair of electrodes. In some forms, at least one of the plurality of organic layers is an emissive layer.

In some forms, the emitter has the chemical structure of:

In some forms, the percentage by weight of the emitter of the emissive layer is 2-6%. In some forms, the percentage by weight of the emitter of the emissive layer is 16-30%. In some forms, the method further comprises mixing the emitter with one or more host materials such that the emissive layer includes a first sub-layer and a second sub-layer. In some forms, the percentage by weight of the emitter of the first sub-layer is 2-6%. In some forms, the percentage by weight of the emitter of the second sub-layer is 16-30%.

In some forms, the first sub-layer includes one host material and the second sub-layer includes two host materials. In some forms, the first sub-layer includes two host materials and the second sub-layer includes two host materials. In some forms, the first sub-layer emits monomer-state emission and the second sub-layer emits aggregation-state emission.

In some forms, the one or more host materials are selected from TcTa, MCP, B3PymPm, and 26Dczppy. In some forms, the OLED device is voltage-driven color tunable from 2.4V to 14V. In some forms, the method further comprises fabricating the plurality of organic layers to include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.

In some forms, the emitter has a chemical structure according to:

wherein X is independently a 5-or 6-membered heterocyclic ring,

wherein R ₁-R ₃ are independently selected from hydrogen, halogen, hydroxyl, an unsubstituted alkyl, a substituted alkyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group, wherein R ₄ is independently selected from the group consisting of hydrogen, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, sulfonyl, phosphino, and combinations thereof,

wherein each pair of adjacent R groups of R ₁-R ₃ are independently one or two separated groups or atoms or are fused to form 5-6 membered ring (s) , and

wherein R ₁-R ₄ represents mono-, di-, tri-, tetra-substitutions, or no substitution.

In some forms, the emitter has a chemical structure according to:

wherein X is selected from

and substituted groups thereof;

wherein R ₅-R ₉ are independently selected from hydrogen, a halogen, a hydroxyl, an unsubstituted alkyl, a substituted alkyl, a cycloalkyl, an unsubstituted aryl, a substituted aryl, an acyl, an alkoxy, an acyloxy, an amino, a nitro, an acylamino, an aralkyl, a cyano, a carboxyl, a thio, a styryl, an aminocarbonyl, a carbamoyl, an aryloxycarbonyl, a phenoxycarbonyl, an alkoxycarbonyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) ₃,

(3, 5-di ^tBu) Ph, fluorine,

wherein R _xand R _y are independently selected from hydrogen, a halogen, a hydroxyl, an unsubstituted alkyl, a substituted alkyl, a cycloalkyl, an unsubstituted aryl, a substituted aryl, an acyl, an alkoxy, an acyloxy, an amino, a nitro, an acylamino, an aralkyl, a cyano, a carboxyl, a thio, a styryl, an aminocarbonyl, a carbamoyl, an aryloxycarbonyl, a phenoxycarbonyl, an alkoxycarbonyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) _3, , (3, 5-di ^tBu) Ph, fluorine or a

and

wherein each pair of adjacent R groups of R ₅-R ₈ are independently one or two separated groups or atoms or are fused to form 5-6 membered ring (s) , and

wherein R ₅-R ₉ represents mono-, di-, tri-, tetra-substitutions, or no substitution.

In some forms, the emitter has a chemical structure according to:

wherein X is selected from

and substituted groups thereof;

wherein Q is an unsubstituted alkyl, a substituted alkyl, an unsubstituted alkenyl, a substituted alkenyl, an unsubstituted alkynyl, a substituted alkynyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group;

wherein R ₁₀-R ₁₃ are independently selected from hydrogen, a halogen, a hydroxyl, an unsubstituted alkyl, a substituted alkyl, a cycloalkyl, an unsubstituted aryl, a substituted aryl, an acyl, an alkoxy, an acyloxy, an amino, a nitro, an acylamino, an aralkyl, a cyano, a carboxyl, a thio, a styryl, an aminocarbonyl, a carbamoyl, an aryloxycarbonyl, a phenoxycarbonyl, an alkoxycarbonyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) ₃,

(3, 5-di ^tBu) Ph, fluorine,

and

wherein each pair of adjacent R groups of R ₁₀-R ₁₂ are independently one or two separated groups or atoms or are fused to form 5-6 membered ring (s) , and

wherein R ₁₀-R ₁₂ represents mono-, di-, tri-, tetra-substitutions, or no substitution.

Additional advantages of the disclosed method and compositions will be set forth in part in the description which follows, and in part will be understood from the description, or may be learned by practice of the disclosed method and compositions. The advantages of the disclosed method and compositions will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the figures of the accompanying drawings which are meant to be exemplary and not limiting, in which like references are intended to refer to like or corresponding parts, and in which:

FIG. 1 presents a graphical representation of the photoluminescence properties of an emitter used in an exemplary color stable OLED device according to one or more embodiments herein;

FIG. 2 presents a diagram showing OLED structure according to one or more embodiments herein;

FIG. 3 presents a compound for use as an OLED emitter according to one or more embodiments herein;

FIG. 4 presents a compound for use as an OLED emitter according to one or more embodiments herein;

FIG. 5A presents a compound for use as an OLED emitter according to one or more embodiments herein;

FIG. 5B presents a graphical representation of the emission spectrum of an exemplary OLED device implementing the compound of FIG. 5A according to one or more embodiments herein;

FIG. 6 presents a compound for use as an OLED emitter according to one or more embodiments herein;

FIG. 7 presents a compound for use as an OLED emitter according to one or more embodiments herein;

FIG. 8 presents a graphical representation of the emission spectrum of the exemplary color stable OLED device;

FIG. 9 presents a graphical representation of the emission spectra of six exemplary OLED devices;

FIG. 10 presents a graphical representation of the emission spectra and electroluminescence properties of another exemplary OLED device;

FIG. 11 presents a graphical representation of the EQE%, power efficiency, and emission spectra of the six additional exemplary OLED devices;

FIG. 12 presents a graphical representation of the emission spectra and electroluminescence properties of another exemplary OLED device;

FIG. 13 presents a graphical representation of the emission spectra and electroluminescence properties of another exemplary OLED device; and

FIG. 14 presents the spectra of OLED device as the voltage was tuned and the OLED device efficiency as a function of luminance.

DETAILED DESCRIPTION OF THE INVENTION

The disclosed method and compositions may be understood more readily by reference to the following detailed description of particular embodiments and the Example included therein and to the Figures and their previous and following description.

I. Definitions

Throughout the specification, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, the phrase “in one embodiment” as used herein does not necessarily refer to the same embodiment and the phrase “in another embodiment” as used herein does not necessarily refer to a different embodiment. Similarly, the phrase “one or more embodiments” as used herein does not necessarily refer to the same embodiment and the phrase “at least one embodiment” as used herein does not necessarily refer to a different embodiment. The intention is, for example, that claimed subject matter includes combinations of example embodiments in whole or in part.

The term “alkyl group” as used herein is a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl and the like. A “lower alkyl” group is an alkyl group containing from one to six carbon atoms. Likewise, “lower alkenyl” and “lower alkynyl” have similar chain lengths. The alkyl groups may also contain one or more heteroatoms within the carbon backbone. Examples include oxygen, nitrogen, sulfur, and combinations thereof. In certain embodiments, the alkyl group contains between one and four heteroatoms. The term “alkyl” includes both “unsubstituted alkyls” and “substituted alkyls” , the latter of which refers to alkyl moieties having one or more substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone. Such substituents include, but are not limited to, halogen, hydroxyl, carbonyl (such as a carboxyl, alkoxycarbonyl, formyl, or an acyl) , thiocarbonyl (such as a thioester, a thioacetate, or a thioformate) , alkoxyl, phosphoryl, phosphate, phosphonate, a phosphinate, amino, amido, amidine, imine, cyano, nitro, azido, sulfhydryl, alkylthio, sulfate, sulfonate, sulfamoyl, sulfonamido, sulfonyl, heterocyclyl, aralkyl, or an aromatic or heteroaromatic moiety.

The term “alkoxy” as used herein is an alkyl group bound through a single, terminal ether linkage; that is, an “alkoxy” group may be defined as -OR where R is alkyl as defined above. A “lower alkoxy” group is an alkoxy group containing from one to six carbon atoms.

The term “alkenyl group” as used herein is a hydrocarbon group of from 2 to 24 carbon atoms and structural formula containing at least one carbon-carbon double bond. Asymmetric structures such as (AB) C=C (CD) are intended to include both theE andZ isomers. This may be presumed in structural formulae herein wherein an asymmetric alkene is present, or it may be explicitly indicated by the bond symbol C. The term “alkenyl” includes both “unsubstituted alkenyls” and “substituted alkenyls” , the latter of which refers to alkenyl moieties having one or more substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone.

The term “alkynyl group” as used herein is a hydrocarbon group of 2 to 24 carbon atoms and a structural formula containing at least one carbon-carbon triple bond. The term “alkynyl” includes both “unsubstituted alkynyls” and “substituted alkynyls” , the latter of which refers to alkynyl moieties having one or more substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone.

The term “aryl group” as used herein is any carbon-based aromatic group including, but not limited to, benzene, naphthalene, etc. The term “aromatic” also includes “heteroaryl group, ” which is defined as an aromatic group that has at least one heteroatom incorporated within the ring of the aromatic group. Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, sulfur, and phosphorus. The aryl group can be substituted or unsubstituted. The aryl group can be substituted with one or more groups including, but not limited to, alkyl, alkynyl, alkenyl, aryl, halide, nitro, amino, ester, ketone, aldehyde, hydroxy, carboxylic acid, or alkoxy.

The term “cycloalkyl group” as used herein is a non-aromatic carbon-based ring composed of at least three carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. The term “heterocycloalkyl group” is a cycloalkyl group as defined above where at least one of the carbon atoms of the ring is substituted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulphur, or phosphorus.

The term “aralkyl” as used herein is an aryl group having an alkyl, alkynyl, or alkenyl group as defined above attached to the aromatic group. An example of an aralkyl group is a benzyl group.

The term “hydroxyalkyl group” as used herein is an alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, halogenated alkyl, or heterocycloalkyl group described above that has at least one hydrogen atom substituted with a hydroxyl group.

The term “alkoxyalkyl group” is defined as an alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, halogenated alkyl, or heterocycloalkyl group described above that has at least one hydrogen atom substituted with an alkoxy group described above.

The term “ester” as used herein is represented by the formula -C (O) OA, where A can be an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The term “carbonate group” as used herein is represented by the formula -OC (O) OR, where R can be hydrogen, an alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, halogenated alkyl, or heterocycloalkyl group described above.

The term “carboxylic acid” as used herein is represented by the formula -C (O) OH.

The term “aldehyde” as used herein is represented by the formula -C (O) H.

The term “keto group” as used herein is represented by the formula -C (O) R, where R is an alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, halogenated alkyl, or heterocycloalkyl group described above.

The term “carbonyl group” as used herein is represented by the formula C=O.

The term “ether” as used herein is represented by the formula AOA ¹, where A and A ¹ can be, independently, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

The terms "carbocycle" or “carbocyclic” as used herein, refer to stable 3, 4, 5, 6, or 7-membered monocyclic or bicyclic or 7-, 8-, 9-, 10-, 11-, 12-, or 13-membered bicyclic or tricyclic rings, any of which may be saturated, partially unsaturated, unsaturated or aromatic. Examplary, but non-limiting, carbocycles can include cyclopropyl, cyclobutyl, cyclobutenyl, cyclopentyl, cyclopentenyl, cyclohexyl, cycloheptenyl, cycloheptyl, cycloheptenyl, adamantyl, cyclooctyl, cyclooctenyl, cyclooctadienyl, [3.3.0] bicyclooctane, [4.3.0] bicyclononane, [4.4.0] bicyclodecane, [2.2.2] bicyclooctane, fluorenyl, phenyl, naphthyl, indanyl, adamantyl, and anthracenyl.

A bridged ring occurs when one or more carbon atoms link two non-adjacent carbon atoms. Preferred bridges are one or two carbon atoms. It is noted that a bridge always converts a monocyclic ring into a bicyclic ring. When a ring is bridged, the substituents recited for the ring may also be present on the bridge. These terms are also intended to include "aryl. "

The terms “heterocycle” or “heterocyclic” , as used herein, refer to a cyclic radical attached via a ring carbon or nitrogen of a monocyclic or bicyclic ring containing 3-10 ring atoms, and preferably from 5-6 ring atoms, containing carbon and one to four heteroatoms each selected from non-peroxide oxygen, sulfur, and N (Y) wherein Y is absent or is H, O, (C _1-4) alkyl, phenyl or benzyl, and optionally containing one or more double or triple bonds, and optionally substituted with one or more substituents. The term “heterocycle” also encompasses substituted and unsubstituted heteroaryl rings. Examples of heterocyclic ring include, but are not limited to, benzimidazolyl, benzofuranyl, benzothiofuranyl, benzothiophenyl, benzoxazolyl, benzoxazolinyl, benzthiazolyl, benztriazolyl, benztetrazolyl, benzisoxazolyl, benzisothiazolyl, benzimidazolinyl, carbazolyl, 4aH-carbazolyl, carbolinyl, chromanyl, chromenyl, cinnolinyl, decahydroquinolinyl, 2H, 6H-1, 5, 2-dithiazinyl, dihydrofuro [2, 3-b] tetrahydrofuran, furanyl, furazanyl, imidazolidinyl, imidazolinyl, imidazolyl, 1H-indazolyl, indolenyl, indolinyl, indolizinyl, indolyl, 3H-indolyl, isatinoyl, isobenzofuranyl, isochromanyl, isoindazolyl, isoindolinyl, isoindolyl, isoquinolinyl, isothiazolyl, isoxazolyl, methylenedioxyphenyl, morpholinyl, naphthyridinyl, octahydroisoquinolinyl, oxadiazolyl, 1, 2, 3-oxadiazolyl, 1, 2, 4-oxadiazolyl, 1, 2, 5-oxadiazolyl, 1, 3, 4-oxadiazolyl, oxazolidinyl, oxazolyl, oxindolyl, pyrimidinyl, phenanthridinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, phenoxathinyl, phenoxazinyl, phthalazinyl, piperazinyl, piperidinyl, piperidonyl, 4-piperidonyl, piperonyl, pteridinyl, purinyl, pyranyl, pyrazinyl, pyrazolidinyl, pyrazolinyl, pyrazolyl, pyridazinyl, pyridooxazole, pyridoimidazole, pyridothiazole, pyridinyl, pyridyl, pyrimidinyl, pyrrolidinyl, pyrrolinyl, 2H-pyrrolyl, pyrrolyl, quinazolinyl, quinolinyl, 4H-quinolizinyl, quinoxalinyl, quinuclidinyl, tetrahydrofuranyl, tetrahydroisoquinolinyl, tetrahydroquinolinyl, tetrazolyl, 6H-1, 2, 5-thiadiazinyl, 1, 2, 3-thiadiazolyl, 1, 2, 4-thiadiazolyl, 1, 2, 5-thiadiazolyl, 1, 3, 4-thiadiazolyl, thianthrenyl, thiazolyl, thienyl, thienothiazolyl, thienooxazolyl, thienoimidazolyl, thiophenyl and xanthenyl.

The term “heteroaryl” , as used herein, refers to a monocyclic aromatic ring containing five or six ring atoms containing carbon and 1, 2, 3, or 4 heteroatoms each selected from non-peroxide oxygen, sulfur, and N (Y) where Y is absent or is H, O, (C ₁-C ₈) alkyl, phenyl or benzyl. Non-limiting examples of heteroaryl groups include furyl, imidazolyl, triazolyl, triazinyl, oxazoyl, isoxazoyl, thiazolyl, isothiazoyl, pyrazolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl, (or its N-oxide) , thienyl, pyrimidinyl (or its N-oxide) , indolyl, isoquinolyl (or its N-oxide) , quinolyl (or its N-oxide) and the like. The term "heteroaryl" can include radicals of an ortho-fused bicyclic heterocycle of about eight to ten ring atoms derived therefrom, particularly a benz-derivative or one derived by fusing a propylene, trimethylene, or tetramethylene diradical thereto. Examples of heteroaryl include, but are not limited to, furyl, imidazolyl, triazolyl, triazinyl, oxazoyl, isoxazoyl, thiazolyl, isothiazoyl, pyraxolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl (or its N-oxide) , thientyl, pyrimidinyl (or its N-oxide) , indolyl, isoquinolyl (or its N-oxide) , quinolyl (or its N-oxide) , and the like.

The term “halogen” , as used herein, refers to fluorine, chlorine, bromine, or iodine.

The term “substituted” as used herein, refers to all permissible substituents of the compounds described herein. In the broadest sense, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic substituents of organic compounds. Illustrative substituents include, but are not limited to, halogens, hydroxyl groups, or any other organic groupings containing any number of carbon atoms, preferably 1-14 carbon atoms, and optionally include one or more heteroatoms such as oxygen, sulfur, or nitrogen grouping in linear, branched, or cyclic structural formats. Representative substituents include alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, phenyl, substituted phenyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, halo, hydroxyl, alkoxy, substituted alkoxy, phenoxy, substituted phenoxy, aroxy, substituted aroxy, alkylthio, substituted alkylthio, phenylthio, substituted phenylthio, arylthio, substituted arylthio, cyano, isocyano, substituted isocyano, carbonyl, substituted carbonyl, carboxyl, substituted carboxyl, amino, substituted amino, amido, substituted amido, sulfonyl, substituted sulfonyl, sulfonic acid, phosphoryl, substituted phosphoryl, phosphonyl, substituted phosphonyl, polyaryl, substituted polyaryl, C ₃-C ₂₀ cyclic, substituted C ₃-C ₂₀ cyclic, heterocyclic, substituted heterocyclic, aminoacid, peptide, and polypeptide groups.

Heteroatoms such as nitrogen may have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the valences of the heteroatoms. It is understood that “substitution” or “substituted” includes the implicit proviso that such substitution is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution results in a stable compound, i.e. a compound that does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc.

Numerical ranges disclosed herein disclose individually each possible number in such range, as well as any sub-ranges and combinations of sub-ranges encompassed therein. For example, a carbon range (i.e., C ₁-C ₁₀) is intended to disclose individually every possible carbon value and/or sub-range encompassed within. For example, a carbon length range of C ₁-C ₁₀ discloses C ₁, C ₂, C ₃, C ₄, C ₅, C ₆, C ₇, C ₈, C ₉, and C ₁₀, as well as discloses sub-ranges encompassed within, such as C ₂-C ₉, C ₃-C ₈, C ₁-C ₅, etc. Similarly, an integer value range of 1-10 discloses the individual values of 1, 2, 3, 4, 5, 6, 7, 8, and 10, as well as sub-ranges encompassed within. Further, ranges, such as external quantum efficiencies, color rendering indices (CRIs) , and power efficiencies, etc. disclose the individual values and fractions thereof, such as 1%, 1.1%, 1.2%, 1.32%, 1.48%etc., as well as sub-ranges encompassed within.

II. Organic Light-Emitting Diodes (OLEDs)

The present disclosure describes platinum emitters (Pt (II) compounds) for use in voltage driven color tunable OLEDs, the OLED devices themselves, and methods of making and using such Pt (II) emitter OLED devices. In one aspect, the OLED devices implement a single emitter as described herein in order to generate light. A single emitter OLED simplifies the device structure and lowers manufacturing costs as compared to multiple-emitter OLEDs or more complicated OLEDs such as those that combine two or more sub-OLEDs. In one or more embodiments described herein, an emitter is provided whose emitting wavelength is variable in response to tuning driving voltage or current to achieve a desirable color or color temperature. As voltage is applied, the OLED produces varying monomer (e.g., 480-530 nm) and excimer (e.g., 600-650nm) emission to produce light having a wavelength along the visible light spectrum (e.g., about 480 nm to 800 nm) . By changing driving voltage or current, the ratio of the emitter’s monomer and excimer emissions can be varied to create different colors. FIG. 1 illustrates exemplary OLED device photoluminescence properties, and in particular it illustrates monomer and excimer ( “aggregation-state emission” ) emission peaks across the visible light spectrum. Here, monomer emission peaks at approximately 510 nm, and the excimer emission peak is at approximately 625 nm.

The emitters and OLED devices described herein advantageously provide light emission characteristics that are suitable for typical OLED device application. The OLED devices as described herein include response rates between 1 μs and 1 ms and can function with voltages as low as 2.4V. In one or more embodiments, the OLED devices produce luminance of 5000 cd/m ² or greater at voltages as low as 5V. In one or more embodiments, the OLED devices achieve EQE of greater than 10%, 15%, 20%, or greater. Further, the OLED devices as described herein can produce color rendering index (CRI) values of 70, 75, 80, 85, 90, 95 or greater using a single platinum emitter described herein.

These characteristics improve upon conventional, multiple-emitter or non-voltage tunable OLED devices. For example, conventional approaches suffer from strong efficiency roll-off and low EQE at luminance between 1000 cd/m ² 5000cd/m ², which are common luminance values in the field. Further, present single-emitter OLED devices fail to achieve CRI values above 80 without resorting to requiring multiple emitters.

It is important to note that the platinum emitters described herein do not implement various conventional tactics to tune color. For example, the emitters do not tune color as a result of doping concentration (i.e., varying the concentrations of polar dopant molecules in the emissive layer or in the host material) . The OLED devices described herein do not implement P-I-N doped layers as is known in the art. The hole transport layers are not p-doped and the electron transport layers are not n-doped.

Further, to produce certain color, the OLEDs described herein do not implement a multiple OLED arrangement in an array which each OLED is particularly tuned such that the average of the colors produces a desired color. Additionally, the OLEDs herein do not rely upon fluorescent molecules inserted into a phosphorescent complex, certain ligands to fine-tune the color of emission, or ligands to trap carriers. Rather, the voltage-dependent color-tunable nature of the OLEDs obviates such approaches.

Notably, the OLED devices described herein also do not include a carrier blocking layer or hole blocking layer disposed between adjacent emission layers in order to provide color tunable functionality. In one or more embodiments, the OLED devices described herein include a single emissive layer and utilize a co-host mixture in the emissive layer. In one or more embodiments, the OLED devices described herein include an emissive layer that can be split into two emissive sub-layers. In a first emissive sub-layer, the emitter and host mixture is chosen to produce monomer emission as the dominant emission. In a second emissive sub-layer, the emitter and host mixture is chosen to produce excimer or aggregation-state emission as the dominant emission.

With reference now to FIG. 2, a color tunable OLED structure 100 having a single emitter as in one or more embodiments described herein is illustrated as a non-limiting example. Methods of manufacturing OLEDs are known. The OLED 100 includes a pair of electrodes corresponding to an anode 105 and a cathode 110 that sandwich a plurality of semiconductor layers between the two electrodes that cause electroluminescence when voltage is applied to the OLED. The anode 105 and cathode 110 comprise metallic materials for conducting electricity, such as the following non-limiting examples: aluminum, gold, magnesium, or barium for the cathode, and indium tin oxide ( “ITO” ) for the anode. The anode 105 and cathode 110 can have thicknesses between 100-200 nm. In one or more embodiments, the anode 105 lays further on top of a suitable substrate 112. The substrate 112 emits the light created by the OLED 100 and is typically made of transparent material. For example, the substrate 112 can be made of glass or a transparent polymer.

A hole injection layer ( “HIL” ) 115 and a hole transport layer ( “HTL” ) 120 are layered on top of the anode 105. These layers play a role in the adjustment of electron/hole injection to attain transport balance of charge carriers in the emissive layer 125 of the OLED 100. In one or more embodiments, the HIL 115 has a thickness between 1-10 nm. In one or more embodiments, the HTL 115 has a thickness between 30-80 nm. The materials for the HIL 115 and HTL 120 are selected to maximize OLED efficiency. As some non-limiting examples, the HIL 115 can comprise molybdenum trioxide ( “MoO ₃” ) or hexaazatriphenylene-hexacarbonitrile ( “HAT-CN” ) , and the HTL 120 can comprise Tris (4-carbazoyl-9-ylphenyl) amine ( “TcTa” ) , N, N′-Di (1-naphthyl) -N, N′-diphenyl- (1, 1′-biphenyl) -4, 4′-diamine ( “NPB” ) or di-4-tolylaminophenyl cyclohexane ( “TAPC” ) . In one or more embodiments, the HTL 120 includes two complementary sub-layers. For example, a first sub-layer of the HTL 120 can include deposited TAPC or NPD, and a second sub-layer can include deposited TcTa. Exemplary compound structures deposited in HIL 115 and HTL 120 are shown below.

Other suitable HIL and/or HTL materials may be used as known in the art.

The emissive layer 125 is arranged on top of HTL 120. In one or more embodiments, the emissive layer 125 has a thickness between 10-30 nm. In one or more embodiments, the emissive layer 125 includes one or more host materials mixed with an emitter formed by the compounds described herein, examples of which are:

The host materials may be formed of a single host (i.e., one host mixed with an emitter) , or may be formed as a co-host mixture (i.e., two hosts mixed with an emitter) . The emitter is added to the host materials as a percentage of total weight. The single emitter emits light when voltage is applied to the emissive layer 125.

In one or more embodiments, the emissive layer 125 is a single layer structure that implements a co-host mixture (e.g., two host materials and an emitter) . In other embodiments, the emissive layer 125 is two separate emissive sub-layers in which an emitter is mixed with one or more hosts in each sub-layer ( “double EMLs” ) . For example, the emissive layer 125 can be a single host double EML, in which a first host is mixed with the emitter in a first emissive sub-layer, and a second host is mixed with the emitter in a second emissive sub-layer. The first host can be the same or different from the second host. In still other embodiments, the emissive layer 125 is a co-host double EML structure in which the first sub-layer includes two host materials mixed with the emitter, and the second sub-layer includes two host materials also mixed with the emitter. The co-host materials in the first and second sub-layers can be the same or different. In still further embodiments, the emissive layer 125 is arranged as a mixed single/co-host double EML. For example, the first sub-layer can include a first host mixed with the emitter, whereas the second sub-layer can include a second host and a third host mixed as co-hosts with the emitter. The first, second and third hosts can be made of the same or different materials. With respect to the emissive layer 125, more than one emitter may be used, as desired, whether emissive layer is formed of a single layer or formed of separate emissive sub-layers.

As some non-limiting examples, the host materials can be TcTa, 1, 3-Bis (N-carbazolyl) benzene ( “MCP” ) , 4, 6-Bis (3, 5-di-3-pyridylphenyl) -2-methylpyrimidine ( “B3PymPm” ) , or 2, 6-bis (3- (9H-Carbazol-9-yl) phenyl) pyridine ( “26Dczppy” ) . Other suitable host materials may be used as known in the art. In certain embodiments, the emissive layer 125 is a single layer structure containing one or more hosts, as described above, and one or more complex emitters (e.g., Pt-X-1 to Pt-X-6) at x%by weight of the host (s) included therein, in which x is between 2%and 30%, 2%and 25%, 2%and 20%, or 2%and 15%. In certain other embodiments, the emissive layer 125 is formed of separate emissive sub-layers each independently containing one or more hosts, as described above, and one or more complex emitters (e.g., Pt-X-1 to Pt-X-6) at x%by weight of the host (s) included therein, in which x is between 2%and 30%, 2%and 25%, 2%and 20%, or 2%and 15%. In a particular embodiment, the emissive layer 125 is a co-host single layer structure that includes TcTa and B3PymPm as co-hosts and a complex emitter (e.g., Pt-X-3 or Pt-X-5) of x%by weight of the hosts, in which x is between 2%and 30%, 2%and 25%, 2%and 20%, or 2%and 15%.

An electron transport layer ( “ETL” ) 130 and an electron injection layer ( “EIL” ) 135 are arranged on top of the emissive layer 125 and below the cathode 110. These layers provide high electron affinity and high electron mobility to the OLED 100 for electrons to flow across the various OLED layers. In one or more embodiments, the ETL 130 has a thickness between 30-80 nm. In one or more embodiments, the EIL 135 has a thickness of 1-5nm. In one or more embodiments, additional electron transporting materials are added to

ETL

130 and 135 to facilitate electron emission. The materials for the ETL 130 and EIL 135 are selected to maximize OLED efficiency. As some non-limiting examples, the ETL 130 can comprise B3PymPm, 1, 3, 5-Tri (m-pyridin-3-ylphenyl) benzene ( “TmPyPb” ) , 2, 4, 6-tris [3′- (pyridin-3-yl) biphenyl-3-yl] -1, 3, 5-triazine ( “TmPPPyTz” ) , or 2, 2′, 2"- (1, 3, 5-Benzinetriyl) -tris (1-phenyl-1-H-benzimidazole) ( “TPBi” ) . As some non-limiting examples, the EIL 135 can comprise LiF, 8-hydroxy-quinolinato lithium ( “Liq” ) , Cs, or CsF.

Other suitable EIL and/or ETL materials may be used as known in the art.

III. Metal Complex Emitters

In one or more embodiments, the emitter used as a dopant in the emissive layer 125, described above, is a metal complex having square planar chemical structure. For example, the metal complex is a platinum (II) complex. Platinum complexes are preferable as they have a rigid ligand scaffold with polydentate chelates to minimize structural distortion upon excitation, have an extended π-conjugation of ligand, have a strong δ-donation (e.g., O^N^C^N with deprotonated C-donor) to ensure strong metal-ligand interaction, and have a high metal-character or charge transfer involvement in the emissive state (i.e., a short emission lifetime for the emitter) . In one or more embodiments, the emitter is a compound having a structure form of Pt (O^N^C^N) .

As shown abovespecific embodiments of platinum emitters suitable for use as a single emitter in an OLED device as described herein are illustrated. Each of Pt-X-1, Pt-X-2, Pt-X-3, Pt-X-4, Pt-X-5, and Pt-X-6 can be mixed with one or more host materials in an emissive layer (e.g., emissive layer 125) . In each of the emitters Pt-X-1, Pt-X-2, Pt-X-3, Pt-X-4, Pt-X-5, and Pt-X-6, the emitter includes an N^C^N ligand and incorporates an additional phenolic/indenyl moiety to the N^C^N mainframe. A strong ligand field presence is created by two strong σ-donations (O-donor and C-donor) . This leads to strong metal-ligand interactions and provides strong emissive properties. Smaller structural distortion is also expected as rigid structure imposed by the fused 6-5-5 membered metallacycles.

Each of the Pt-X-1, Pt-X-2, Pt-X-3, Pt-X-4, Pt-X-5, and Pt-X-6 emitters, are platinum complexes (Pt (II) ) .

In one or more embodiments, the emitter is a platinum (II) complex which has a base structure as follows:

In one or more embodiments, X is independently a 5-or 6-membered carbocyclic or heterocyclic ring. In one or more embodiments, R ₁-R ₃ are independently selected from hydrogen, halogen, hydroxyl, an unsubstituted alkyl, a substituted alkyl, an unsubstituted alkenyl, a substituted alkenyl, an unsubstituted alkynyl, a substituted alkynyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group. In one or more embodiments, R ₄ is independently selected from the group consisting of hydrogen, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, sulfonyl, phosphino, and combinations thereof. In one or more embodiments, R ₁-R ₄ are independently selected from hydrogen, a halogen, an alkyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) ₃,

(3, 5-di ^tBu) Ph, fluorine,

In one or more embodiments, R _x and R _y are independently selected from the group consisting of hydrogen, halide, alkyl, cycloalky, heteroalkyl, arylalky, alkoxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids ester, nitrile, isonitrile, sulfanyl, sulfinyl, phosphino, and combinations thereof. In one or more embodiments of the above base structure, two or more adjacent R ₁, R ₂, R ₃, R ₄ can be optionally joined to form a fused ring. For example, R ₁and R ₂ may form a fused ring, such as in Pt-X-1 and Pt-X-2. In one or more embodiments, each pair of adjacent R groups of R ₁-R ₄ are independently two separated groups (or atoms) or one group (or atom) , and form 5-6 membered ring (s) . In one or more embodiments, R ₁-R ₄ represents one or more substitutions, such as mono-, di-, tri-, tetra-substitutions, or no substitution.

In one or more other embodiments, the emitter is a platinum (II) complex which has a base structure as follows:

In one or more embodiments, R ₆-R ₈ are independently selected from hydrogen, halogen, hydroxyl, an unsubstituted alkyl, a substituted alkyl, an unsubstituted alkenyl, a substituted alkenyl, an unsubstituted alkynyl, a substituted alkynyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group. In one or more embodiments, R ₄ is independently selected from the group consisting of hydrogen, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, sulfonyl, phosphino, and combinations thereof. In one or more embodiments, X is independently a 5-or 6-membered carbocyclic or heterocyclic ring. In certain embodiments, X can be selected from

and substituted groups thereof. In one or more embodiments, R ₅-R ₉ are independently selected from hydrogen, a halogen, an alkyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) ₃,

(3, 5-di ^tBu) Ph, fluorine,

In one or more embodiments, R _x and R _y are independently selected from the group consisting of hydrogen, halide, alkyl, cycloalky, heteroalkyl, arylalky, alkoxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids ester, nitrile, isonitrile, sulfanyl, sulfinyl, phosphino, and combinations thereof. In one or more embodiments of the above base structure, two or more adjacent R ₅, R ₆, R ₇, R ₈, R ₉ can be optionally joined to form a fused ring. In one or more embodiments, each pair of adjacent R groups of R ₅-R ₉ are independently two separated groups (or atoms) or one group (or atom) , and form 5-6 membered ring (s) . In one or more embodiments, R ₅-R ₉ represents one or more substitutions, such as mono-, di-, tri-, tetra-substitutions, or no substitution.

In one or more embodiments, R ₁₀-R ₁₃ are independently selected from hydrogen, halogen, hydroxyl, an unsubstituted alkyl, a substituted alkyl, an unsubstituted alkenyl, a substituted alkenyl, an unsubstituted alkynyl, a substituted alkynyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group. In one or more embodiments, each Y group is independently a 5-or 6-membered carbocyclic or heterocyclic ring. In some instances, Q is an unsubstituted alkyl, a substituted alkyl, an unsubstituted alkenyl, a substituted alkenyl, an unsubstituted alkynyl, a substituted alkynyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group. In some instances, Q is an alkynl group, such as a cyano group. In certain embodiments, X can be selected from

and substituted groups thereof. In one or more embodiments, R ₁₀-R ₁₃ are independently selected from hydrogen, a halogen, an alkyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) ₃,

(3, 5-di ^tBu) Ph, fluorine,

In one or more embodiments, R _x and R _y are independently selected from the group consisting of hydrogen, halide, alkyl, cycloalky, heteroalkyl, arylalky, alkoxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids ester, nitrile, isonitrile, sulfanyl, sulfinyl, phosphino, and combinations thereof. In one or more embodiments of the above base structure, two or more adjacent R ₁₀, R ₁₁, R ₁₂, R ₁₃ can be optionally joined to form a fused ring. In one or more embodiments, each pair of adjacent R groups of R ₅-R ₉ are independently two separated groups (or atoms) or one group (or atom) , and form 5-6 membered ring (s) . In one or more embodiments, R ₅-R ₉ represents one or more substitutions, such as mono-, di-, tri-, tetra-substitutions, or no substitution.

IV. Voltage-Dependent Color Tunability of OLEDs

In one aspect, the emitters described herein are voltage-dependent tunable emitters and utilize the different states of single emitter to create light of different colors across the visible light spectrum. The compounds herein produce white light by applying voltage to produce complementary monomer and aggregation-state (e.g., excimer) emission when excited. This balance produces a high photoluminescence quantum yield and has a short emission lifetime (on the order of 100ns to 10 μs) , which lead to a high CRI and produce highly efficient OLED lighting. In one or more embodiments, the devices described herein can additionally utilize double host doping or double emissive layers to increase the color tuning range greatly, increase brightness (>80,000 cd/m ²) and suppress efficiency roll-off at high luminance (from 1000 cd/m ² to 5000 cd/m ²) . Double host doping (or co-host doping) is when a complex dopant is added to a two host mix within a single emissive layer.

Monomer and excimer emission can be amplified or suppressed by fabricating an emissive layer having different emitter doping concentrations. For example, at low doping concenrations (e.g., between 2-6%by weight of the emissive layer) monomer emission dominates and causes the OLED device to be more color stable toward wavelengths of 480-530 nm as it is voltage-tuned. At higher doping concentrations (e.g., between 15-30%by weight of the emissive layer, and more particularly 20-25%by weight) , excimer emission dominates and the OLED device is more color stable toward 600-700 nm. By implementing a double EML, the OLED device can be spread across the visible light spectrum.

In one aspect, a method for creating a voltage-dependent color-tunable OLED device having a single emitter that produces white light is provided. To form white light, the OLED device combines emissions from two sources within the single emitter. In some embodiments, the single emitter produces emissions from a monomer state and an excimer state. In other embodiments, the single emitter includes additional host materials to facilitate production of emissions from a monomer state and an exciplex state. In still other embodiments, the single emitter simultaneously produces emissions of high-energy fluorescence between 450nm and 550nm and low-energy phosphorescence between 560nm and 700nm under different driving voltages or currents.

The method continues by applying low voltage from 2.4V to 6V to the emitter to produce emissions from one of the two emission sources. For example, at low voltage, emissions are dominated by low-energy excimer emission, exciplex emission or phosphorescence emission, depending on the embodiment. At low voltage, the OLED device emits primarily longer wavelength light in the visible spectrum, such as red or orange light. However, as driving voltage is increased from 6V to 12V, the emissions emit a greater amount of high-energy monomer-state light and/or fluorescence. The more the voltage is increased, the more the high-energy emissions dominate over the low-energy emissions, and the result is a shorter wavelength of emitted light. For example, at a voltage of 3V, the OLED device produces a wavelength of 650 nm, while at a voltage of 8V, it produces a wavelength of 515nm. In thisway, the single emitter’s emission state can be varied to tune the OLED to different colors by varying the driving voltage higher or lower.

In one or more embodiments, the EQE can range between 15-20%or 20-25%. This is advantageous as conventional color-tunable OLED emitters typically have an EQE of less than 15%. In one or more embodiments, the low efficiency roll-off is in the range of 1000-5000 cd/m ².

Examples

The following are examples that illustrate embodiments for practicing the disclosure described herein. These examples should not be construed as limiting. The examples were performed using OLED devices having the plurality of layers, composition and materials as in OLED 100 and in which the platinum complex used as an emitter had a percentage by weight of the emissive layer of 2-30%. Each OLED included an anode 105, cathode 110, HIL 115, HTL 120, ETL 130, and EIL 135 as described herein. The emissive layer for each device was varied according to emitter and host material to produce different voltage-dependent color-tunable OLED devices.

For devices having a low emitter concentration (4wt%) , only monomer emission takes place, and as such, the emitter is color stable as the voltage is increased. FIG. 4 illustrates an exemplary color stable emission spectrum of a Pt-X-2 emitter doped at 4wt%OLED as voltage is increased from 3V to 14V in 1V increments. As can be seen, intensity peaks around 520 nm, and drops down after that, regardless of voltage. This clear peak is created because by using a low emitter doping concentration of 4%by weight, each Pt (II) molecule is separated by the host. The interaction between Pt (II) molecules is then weak, and the Pt emitter produces only monomers in the emissive layers, and thus only monomer emission can be observed across the driving voltage range (e.g., between 3V and 10V) . Therefore, this OLED device can be said to be color stable. The described experiments harmonize such color stability properties with

OLEDs based on Pt-X-5

a. Experiment 1

In a first example, the compound Pt-X-5 was prepared as an emitter in six OLED devices as described herein, each device having a different emissive layer. The OLED devices were fabricated according to the following structure: an ITO anode, a 100nm aluminum cathode, a 2nm MoO ₃ HIL layer, a 50nm TAPC HTL layer, an additional 10nm TcTa HTL layer, a 50nm B3PymPm ETL layer, and a 1.2nm LiF EIL layer. The emissive layer for each of the six devices was then prepared using TcTa and B3PymPm as host materials. Five of the OLED devices were prepared as double EMLs, and one was prepared having a single emissive layer. Table 1 below illustrates the varying emitter amounts by weight. For example, device 1 had 4%Pt-X-5 as compared to TcTa and 18%by weight as compared to B3PymPm.

Table 1

Voltage was then applied to each device and the intensity and wavelength of the emission was observed as the voltage was varied between 3V and 8V in 0.5V increments. The emission spectrum changes for each of the six devices are illustrated in FIG. 5 and show how intensity as a function of wavelength varied as the voltage was varied. For example, at low voltages (e.g., 2.5V-4V) , the intensity peaks are approximately 640nm-700nm, which corresponds to red light. However, at high voltages (e.g., 6V-8V) , the intensity peaks at approximately 500-550 nm, which corresponds to blue, green, and yellow light. In this way, different colors were produced by the OLED devices as a function of voltage.

Table 1 also illustrates additional information regarding emissive layer composition, the EQE%, the maximum power efficiency, the maximum luminance, the minimum voltage to initiate OLED emission ( “Turn-on voltage” at 1 cd/m2) , and the color according to the International Commission on Illumination (CIE) x, y coordinate system. As can be seen, each of the six devices maintained an EQE%of greater than 15%for luminance over 1000 cd/m ² and includes a CRI of over 90. This stands in comparison to conventional color-tunable OLED devices, which cannot maintain EQE%beyond 15%at greater than 1000 cd/m ², and which the best devices do not have CRIs of greater than 70, and more typically are in the 40-70 range.

b. Experiment 2

In a second example, a Pt-X-5 emitter was used to prepare a double EML OLED device. The OLED device was fabricated according to the following structure: an ITO anode, a 100nm aluminum cathode, a 2nm MoO ₃ HIL layer, a 50nm TAPC HTL layer, an additional 10nm TcTa HTL layer, a 50nm TmPyPB ETL layer, and a 1.2nm LiF EIL layer. The double EML consisted of a 10nm first sub-layer of TcTa mixed with 4%Pt-X-5 by weight and a 10nm second sub-layer of 26Dczppy mixed with 20%Pt-X-5 by weight. The voltage was then varied from 5V to 17V in 2V increments. The spectra of this OLED device as the voltage was tuned and the OLED device efficiency as a function of luminance is shown in FIG. 6. The properties of this OLED device during this experiment are shown in the below Table 2.

Table 2

OLEDs based on Pt-X-3

c. Experiment 3

A third experiment was performed in which six additional OLED devices were fabricated implementing a single emitter of the form in compound Pt-X-3. The OLED devices in this example were fabricated according to the following structure: an ITO anode, a 100nm aluminum cathode, a 2nm MoO ₃ HIL layer, a 50nm TAPC HTL layer, an additional 10nm TcTa HTL layer, a 50nm B3PymPm ETL layer, and a 1.2nm LiF EIL layer. The six OLED devices were prepared implementing Pt-X-3 as a single emitter mixed with TcTa and B3PymPm as co-host materials. In this experiment, each of the six devices included different compositions of Pt-X-3 by weight, as illustrated by Table 3 below. Device 1 was a color stable OLED device for reference (as in FIG. 4) ; however, each of the rest of the devices were voltage-dependent color-tunable. Each of the six devices included a single emissive layer, except for device 4, which instead was a double EML. In the first emissive sub-layer of device 4, the Pt-X-3 emitter was 4%by weight as compared to TcTa. In the second emissive sub-layer, the Pt-X-3 emitter was 18%by weight as compared to B3PymPm. The voltage was then varied between 3V and 10V in 1V increments and the intensity was observed. Graphs of the EQE%, power efficiency, and emission spectra of the different devices are shown by FIG. 7.

Table 3

OLEDs based on Pt-X-2

d. Experiment 4

In a fourth example, a Pt-X-2 emitter was used to prepare a double EML OLED device having a CRI between 75-85. The OLED device was fabricated according to the following structure: an ITO anode, a 100nm aluminum cathode, a 2nm MoO ₃ HIL layer, a 50nm TAPC HTL layer, an additional 10nm TcTa HTL layer, a 50nm TmPyPB ETL layer, and a 1.2nm LiF EIL layer. The double EML consisted of a 10nm first sub-layer of co-hosts TcTa and B3PymPm mixed with 4%Pt-X-2 by weight and a 10nm second sub-layer of co-hosts TcTa and B3PymPm mixed with 25%Pt-X-2 by weight. The voltage was then varied from 3V to 10V in 1V increments. The spectra of this OLED device as the voltage was tuned and the OLED device efficiency as a function of luminance is shown in FIG. 9. The monomer peak can be seen at approximately 480 nm and the excimer peak at approximately 640 nm. The properties of this OLED device during this experiment are shown in the below Table 4.

Table 4

e. Experiment 5

In a fifth example, a Pt-X-2 emitter was used to prepare a double EML OLED device having a CRI between 75-87. The OLED device was fabricated according to the following structure: an ITO anode, a 100nm aluminum cathode, a 2nm MoO ₃ HIL layer, a 50nm TAPC HTL layer, an additional 10nm TcTa HTL layer, a 50nm TmPyPB ETL layer, and a 1.2nm LiF EIL layer. The double EML consisted of a 10nm first sub-layer of host TcTa mixed with 4%Pt-X-2 by weight and a 10nm second sub-layer of host 26Dczppy mixed with 20%Pt-X-2 by weight. The voltage was then varied from 5V to 15V in 2V increments. The spectra of this OLED device as the voltage was tuned and the OLED device efficiency as a function of luminance is shown in FIG. 10. The monomer peak can be seen at approximately 480 nm and the excimer peak at approximately 640 nm. The properties of this OLED device during this experiment are shown in the below Table 5.

Table 5

OLEDs based on Pt-X-6

d. Experiment 6

In a sixth example, a Pt-X-6 emitter was used to prepare a double EML OLED device having a CRI between 72-78. The OLED device was fabricated according to the following structure: an ITO anode, a 100nm aluminum cathode, a 2nm MoO ₃ HIL layer, a 50nm TAPC HTL layer, an additional 10nm TcTa HTL layer, a 50nm TmPyPB ETL layer, and a 1.2nm LiF EIL layer. The double EML consisted of a 5～15 nm first sub-layer of host TcTa or CzSi mixed with 4% Pt-X-2 by weight and a 5～15 nm second sub-layer of host 26Dczppy mixed with 15～30%Pt-X-6 by weight. The voltage was then varied from 5V to 15V in 1V increments. The spectra of this OLED device as the voltage was tuned and the OLED device efficiency as a function of luminance is shown in FIG. 14. The monomer peak can be seen at approximately 440 nm and the excimer peak at approximately 580 nm. The properties of this OLED device during this experiment are shown in the below Table 6.

Table 6

The foregoing description of the specific embodiments will so fully reveal the general nature of the disclosure that others can, by applying knowledge within the skill of the relevant art (s) (including the contents of the documents cited and incorporated by reference herein) , readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance presented herein, in combination with the knowledge of one skilled in the relevant art (s) .

While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example, and not limitation. It would be apparent to one skilled in the relevant art (s) that various changes in form and detail could be made therein without departing from the spirit and scope of the disclosure. Thus, the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

A method for voltage-tuning an OLED device having a pair of electrodes having opposing polarity, a plurality of organic layers disposed between the pair of electrodes, wherein at least one of the plurality of organic layers is an emissive layer, and wherein the emissive layer includes a single emitter mixed with one or more host materials, wherein the emitter is an organic luminescent material or a metal complex that emits fluorescence or phosphorescence and the emitter has both monomer-state emission and aggregation-state emission, the method comprising:

(a) providing a first voltage to the OLED device to cause the OLED device to emit a first color with a first wavelength; and

(b) adjusting the first voltage to a second voltage to the device to cause the OLED device to emit a second color with a second wavelength.
The method according to claim 1, wherein the first voltage and the second voltage have a difference of 1V.
The method according to claim 1, wherein the first voltage is 2.4V or greater.
A method for making a voltage-tunable OLED device having a pair of electrodes having opposing polarity, a plurality of organic layers disposed between the pair of electrodes, wherein at least one of the plurality of organic layers is an emissive layer, the method comprising:

obtaining an emitter wherein the emitter is organic luminescent material or metal complex, which can emit fluorescence or phosphorescence, and has both monomer-state emission and aggregation-state emission; and

mixing the emitter with one or more host materials to fabricate the emissive layer,

wherein the percentage by weight of the emitter of the emissive layer is 2-30%.
The method according to claim 4, wherein the emitter has the chemical structure of Pt-X-1, Pt-X-2, Pt-X-3, Pt-X-4, Pt-X-5 or Pt-X-6.
The method according to claim 4, wherein the percentage by weight of the emitter of the emissive layer is 2-6%.
The method according to claim 4, wherein the percentage by weight of the emitter of the emissive layer is 16-30%.
The method according to claim 4, further comprising mixing the emitter with one or more host materials such that the emissive layer includes a first sub-layer and a second sub-layer.
The method according to claim 8, wherein the percentage by weight of the emitter of the first sub-layer is 2-6%.
The method according to claim 8, wherein the percentage by weight of the emitter of the second sub-layer is 16-30%.
The method according to claim 8, wherein the first sub-layer includes one host material and the second sub-layer includes two host materials.
The method according to claim 8, wherein the first sub-layer includes two host materials and the second sub-layer includes two host materials.
The method according to claim 8, wherein the first sub-layer emits monomer-state emission and the second sub-layer emits aggregation-state emission.
The method according to claim 4, wherein the one or more host materials are selected from TcTa, MCP, B3PymPm, and 26Dczppy.
The method according to claim 4, wherein the OLED device is voltage-driven color tunable from 2.4V to 14V.
The method according to claim 4, further comprising fabricating the plurality of organic layers to include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.
The method according to claim 4, wherein the emitter has a chemical structure according to:

wherein X is independently a 5-or 6-membered heterocyclic ring,

wherein R ₁-R ₃ are independently selected from hydrogen, halogen, hydroxyl, an unsubstituted alkyl, a substituted alkyl, cycloalkyl, an unsubstituted aryl, a substituted aryl, acyl, alkoxy, acyloxy, amino, nitro, acylamino, aralkyl, cyano, carboxyl, thio, styryl, aminocarbonyl, carbamoyl, aryloxycarbonyl, phenoxycarbonyl, or an alkoxycarbonyl group,

wherein R ₄ is independently selected from the group consisting of hydrogen, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, sulfonyl, phosphino, and combinations thereof,

wherein each pair of adjacent R groups of R ₁-R ₃ are independently one or two separated groups or atoms, selected to form 5-6 membered ring (s) , and

wherein R ₁-R ₃ represents mono-, di-, tri-, tetra-substitutions, or no substitution.
The method according to claim 4, wherein the emitter has a chemical structure according to:

wherein X is selected from

wherein R ₁-R ₄ are independently selected from hydrogen, a halogen, a hydroxyl, an unsubstituted alkyl, a substituted alkyl, a cycloalkyl, an unsubstituted aryl, a substituted aryl, an acyl, an alkoxy, an acyloxy, an amino, a nitro, an acylamino, an aralkyl, a cyano, a carboxyl, a thio, a styryl, an aminocarbonyl, a carbamoyl, an aryloxycarbonyl, a phenoxycarbonyl, an alkoxycarbonyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) ₃,
(3, 5-di ^tBu) Ph, fluorine or a

wherein R ₅ is independently selected from hydrogen, a halogen, a hydroxyl, an unsubstituted alkyl, a substituted alkyl, a cycloalkyl, an unsubstituted aryl, a substituted aryl, an acyl, an alkoxy, an acyloxy, an amino, a nitro, an acylamino, an aralkyl, a cyano, a carboxyl, a thio, a styryl, an aminocarbonyl, a carbamoyl, an aryloxycarbonyl, a phenoxycarbonyl, an alkoxycarbonyl, an ethyl, a butyl, a tert-butyl, -C- (CH ₃) _3, , (3, 5-di ^tBu) Ph, fluorine or a
and

each pair of adjacent R groups of R ₁–R ₄forms 5–8 member ring (s) with other carbon or nitrogen atoms.