TWI523119B - Self cleaning large scale method and furnace system for selenization of thin film photovoltaic materials - Google Patents

Description

Self-cleaning large scale method and furnace system for selenization of thin film photovoltaic materials

The present invention generally relates to photovoltaic technology. More specifically, the present invention provides a method for using copper indium diselenide material (or indium copper selenide, CIS), copper indium gallium diselenide material (or copper indium gallium selenide, CIGS) and/or other substances. Method and structure of a thin film photovoltaic device. The invention can be applied to photovoltaic modules, flexible sheets, glass for buildings or windows, automobiles, and the like.

In the manufacture of films of the CIS and/or CIGS type, there are various manufacturing difficulties, such as maintaining the structural integrity of the substrate material, ensuring uniformity and fineness of the film material, and the like. While some of these problems have been solved by past traditional techniques, they are often insufficient in many cases. Among other things, systems used to make CIS and/or CIGS films (eg, processing chambers) are often difficult to clean. Accordingly, there is a desire for improved systems and methods for fabricating thin film photovoltaic devices.

The present invention generally relates to photovoltaic technology. More specifically, the present invention provides a method and structure for a thin film photovoltaic device using copper indium diselenide material (CIS), copper indium gallium diselenide material (CIGS), and/or other materials. The invention can be applied to photovoltaic modules, flexible sheets, glass for buildings or windows, automobiles, and the like.

According to one embodiment, the present invention provides a method of manufacturing a copper indium diselenide semiconductor film using a self-cleaning furnace. The method includes transferring a plurality of substrates into a furnace, the furnace including a processing region and at least one end cap region detachably coupled to the processing region, the plurality of substrates being vertically oriented with respect to a direction of gravity, with a number N A plurality of substrates are defined, wherein N is greater than 5, and each substrate has a copper and indium composite structure. The method also includes introducing a gaseous substance comprising a hydrogen species and a selenide species and a carrier gas into the furnace, and transferring the thermal energy into the furnace to raise the temperature from the first temperature to a second temperature, the second temperature being range From about 350 ° C to about 450 ° C, a copper indium diselenide film is at least initially formed from a copper and indium composite structure on each substrate. The method further includes decomposing residual selenide species in an interior region of the treated region of the furnace. The method further includes depositing elemental selenide species in the vicinity of the end cap region operable at the third temperature. Moreover, the method includes maintaining the inner region substantially free of elemental selenide species by decomposing residual selenide species from at least the interior region of the processing region.

In a specific embodiment, hydrogen selenide gas is used as a working gas in the furnace. When the temperature is about 400 ° C or higher, the hydrogen selenide gas is thermally activated to pyrolyze it to form elemental selenium (Se) or selenium clusters (Se ₂ or Se ₃ ). The end cap region includes a lid that is cooled by flowing living water and heated by a lamp to control the temperature of the lid. The temperature of the monitor lid is kept cool to serve as a "cryopump" so that selenium species (elemental selenium and selenium clusters) can be deposited on the lid and inhibit the reaction between selenium and other membrane materials such as indium. After completing one or more of the processing loops, the lid of the end cap region may be further cleaned with a cloth (eg, linen, or the like) to remove deposited selenium residues and particles.

It should be understood that the present invention provides many benefits over conventional techniques. Among other things, the system and method of the present invention are compatible with conventional systems, which enables cost savings. In various embodiments, the residual gas is incorporated into a particular region of the processing chamber so that cleaning can be readily performed. There are also other benefits.

The present invention generally relates to photovoltaic technology. More specifically, the present invention provides a method and structure for using copper indium diselenide materials (CIS), copper indium gallium diselenide materials (CIGS), and/or other thin film photovoltaic devices. The invention can be applied to photovoltaic modules, flexible sheets, glass for buildings or windows, automobiles, and the like.

1 is a simplified diagram of a transparent substrate having overlapping electrode layers in accordance with an embodiment of the present invention. This figure is only an embodiment, and it should not limit the scope of the claims herein. As shown, the structure 100 includes a transparent substrate 104 . In one embodiment, the substrate 104 can be a glass substrate, such as soda lime glass. However, other types of substrates can also be used. Examples of substrates include borosilicate glass, acrylic glass, sugar glass, specialty Corning ^TM glass. As shown, a contact layer comprising metal electrode layer 102 is deposited on substrate 104 . According to one embodiment, the metal electrode layer 102 comprises a metallic material characterized by having a predetermined conductivity based on a solar cell application-based film. The metal electrode layer 102 can be deposited in various ways depending on the application. For example, the metal electrode layer 102 mainly includes a molybdenum film deposited by sputtering. For example, the thickness can range from 200 to 700 nm. A thin film of material can be deposited on the substrate using a sputtering device (eg, a DC magnetron sputtering device). Such devices are well known and commercially available. However, it should be understood that other types of devices and/or methods may be used, such as evaporation in a vacuum based environment. As an embodiment, a sputter deposition method will be described below.

Sputter deposition is a physical vapor deposition (PVD) method of depositing a thin film by sputtering or ejecting a material from a "target (target)" or source and then depositing it on a substrate (eg, a germanium wafer or glass). The sputtered atoms ejected from the target have a broad energy distribution, typically up to a few 10 eV (100,000 K). By varying the background air pressure, the entire range from high energy ballistic impact to low energy thermal motion can be obtained. The sputtering gas is typically an inert gas such as argon. In order to effectively perform the momentum transfer, the atomic weight of the sputtering gas should be close to the atomic weight of the target, and therefore, ruthenium is preferred for sputtering light elements, and ruthenium or osmium is used for heavy elements. A reactive gas can also be used to sputter the compound. Depending on the process parameters, compounds can be formed on the target surface, in flight, or on the substrate. The availability of many of the parameters controlling sputter deposition makes it a complex process, but also allows the skilled artisan to control the growth and microstructure of the film to a large extent.

2 is a simplified diagram of a composite structure including copper and indium materials in accordance with an embodiment of the present invention. This figure is only an example and the scope of the claims should not be limited herein. In this embodiment, structure 200 includes a glass substrate 208 , preferably soda lime glass, having a thickness of about 1 to 3 mm. For example, the glass substrate 208 serves as a support layer. A metal layer 206 is deposited on the substrate 208 . For example, metal layer 206 acts as a metal electrode layer to provide electrical contact. For example, layer 206 primarily comprises a molybdenum film that has been deposited by sputtering and has a thickness of 200 to 700 nm. In a specific embodiment, an initial chromium film is first deposited on the glass 208 . For example, a chrome layer is provided to ensure good bonding of the entire structure to the substrate 208 . Other types of materials can also be used in the barrier layer, such as hafnium oxide, tantalum nitride, and the like. Layers 204 and 202 primarily comprise a copper layer and an indium layer deposited on metal layer 206 by a sputtering process. As shown in FIG. 2, the indium layer covers the copper layer. However, it should be understood that other arrangements are possible. In another embodiment, the copper layer covers the indium layer. As an example, a thin film of material (e.g., layers 202 , 204, and/or 206 ) is deposited on a substrate using a sputtering apparatus (e.g., a DC magnetron sputtering apparatus). It should be understood that various types of sputtering devices can be used. Such devices are well known and commercially available. Other materials can also be used. It should be understood that the techniques described throughout this application are flexible and that other types of devices and/or methods may be used, such as evaporation of copper and indium materials in a vacuum-based environment. In some embodiments, a deposited gallium material (not shown in Figure 2) can be formed in addition to the copper and indium materials. According to one embodiment, the ratio of copper to indium material is less than one (eg, 0.92 to 0.96); that is, less than one part of copper per indium material.

As an embodiment, structure 200 is formed by processing structure 100 . For example, Cu and In are deposited on structure 100 to form structure 200 . As described above, a copper and/or indium layer is formed by a sputtering process. In the embodiment shown in Figure 2, the Cu film and the In film are shown as two separate layers. In another embodiment, as shown in FIG. 2A, a Cu/In composite or a Cu/In alloy is formed during the sputtering process. It should be understood that the techniques described throughout this application are flexible and that other types of devices and/or methods may be used, such as evaporation of copper and indium materials in a vacuum-based environment. In some embodiments, a deposited gallium material (not shown in Figure 2) can be formed in addition to the copper and indium materials.

2A is a simplified diagram of a composite structure 210 including a composite film of copper and indium, in accordance with another embodiment of the present invention. This figure is only an example and should not limit the scope of the claims herein. As shown, structure 210 includes a transparent substrate 216 . In one embodiment, the substrate 216 can be a glass substrate, such as soda lime glass. The back contact (back contact) includes a metal electrode layer 214 deposited on the substrate 216 . For example, layer 214 primarily includes a film of molybdenum material deposited by sputtering. In one embodiment, an initial chromium film is deposited on the glass 216 prior to depositing the molybdenum material to provide a good bond of the entire structure to the substrate 210 . Layer 212 primarily comprises a copper indium alloy or a copper indium composite. For example, the mixing or alloying of copper indium results in improved uniformity or advantageous morphology of the composite copper indium film. This modified structure is loaded into the desired CIS film after the selenization step. According to one embodiment, a copper indium alloy material is formed from separate layers of copper and indium materials that diffuse into each other. For example, the process of forming a copper indium alloy material can be promoted by subjecting the structure to high temperatures.

3 is a simplified diagram of a furnace in accordance with an embodiment of the present invention. This figure is only an example, which should not limit the scope of the patent application herein. As shown, the furnace 300 includes a process chamber 302 and an end cap 304 of the chamber. According to one embodiment, the reaction chamber 302 is characterized by a volume greater than 200 liters. The inner surface and the spatial region of the processing chamber 302 are depicted as an internal processing region 320 . In one embodiment, the processing chamber 302 can include a quartz tube. End cap region 322 represents the inner surface of end cap 304 and a surface that is partially exposed to the tube of inner processing region 320 . In one embodiment, the end cap 304 can be made of a metallic material. In certain embodiments, end cap 304 and processing chamber 302 are characterized by different surface reactivity, thermal conductivity, viscosity, and/or other characteristics. For example, under certain conditions, various types of materials may be deposited on the end cap 304 rather than on the inner surface of the chamber 302 that is directly exposed to the sample or substrate to be loaded into the chamber. In a specific embodiment, the end cap region 302 is made of a material having a lower specific heat than the processing chamber 302 . As shown in FIG. 3, the furnace 300 includes a vacuum pumping machine including a turbo molecular pump 310 and a rotary pump 312 . Depending on the application, the vacuum pumping machine can be implemented by a combination of a mechanical booster pump and a dry pump. For example, a feed gas and/or a diluent gas (eg, helium, nitrogen, argon, or hydrogen) may be introduced into the process chamber 302 via a gas injection conduit 314 if desired for a particular application and/or process. 312 turbo-molecular pump 310 defining a cavity 302 is evacuated via a rotary pump, a rotary pump 312 via valve 318 and the conductance valve 316 is connected with the manifold. For example, there are no dedicated baffles in the manifold or in the reaction furnace. A heating element 306 is mounted external to the reaction chamber 302 .

Furnace 300 can be used in many applications. According to one embodiment, furnace 300 is used to apply thermal energy to various types of substrates and to introduce various types of gaseous materials. In one embodiment, one or more glass sheets or substrates are positioned vertically adjacent the center of the chamber 302 . As an example, substrate 308 can be similar to those described in Figures 2 and 2A (e.g., a Cu/In layer or a composite Cu/In layer overlying a metal contact layer on a substrate). Gas comprising selenium (e.g., H ₂ Se) in the presence of the layers in the processing chamber. After annealing the material for a given period of time, copper, indium, and selenium diffuse and react with each other to form a high quality copper indium diselenide (CIS) film.

4 is a simplified diagram of a process for forming a copper indium diselenide layer in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the claims herein. Many other variations, modifications, and alternatives will be apparent to those of ordinary skill in the art. It is to be understood that the embodiments and the embodiments described herein are for illustrative purposes only and that it is intended to The spirit and scope of the invention and the scope of the appended patent application.

As shown in Figure 4, the method can be summarized briefly below.

Start

2. providing a plurality of substrates having a composite structure of copper and indium;

3. Introducing a gaseous substance including a hydrogen substance and a selenium substance and a carrier gas into the furnace;

4. transferring thermal energy into the furnace to raise the temperature from the first temperature to the second temperature;

5. maintaining the temperature at about the second temperature for a period of time;

6. Decompose any residual selenide material in the inner region of the treated area of the furnace;

7. Lower the temperature to the third temperature;

8. maintaining the temperature at about the third temperature for a period of time;

9. depositing elemental selenium species in the vicinity of the end cap region operable at the third temperature;

10. Lowering the temperature from the third temperature gradient to approximately the first temperature;

11. Remove the gas;

12. Stop.

These steps are only examples and should not limit the scope of the invention. Many other variations, modifications, and alternatives will be apparent to those of ordinary skill in the art. For example, various steps outlined above may be added, removed, modified, rearranged, repeated, and/or overlapped as contemplated within the scope of the invention. As shown, method 400 begins at start step 402 . Here, the user of the method begins with a processing chamber such as those mentioned above, as well as other steps. The processing chamber can be maintained at about room temperature prior to carrying out the method.

Step 402 is to transfer a plurality of substrates into the processing chamber. Each of the plurality of substrates may be disposed to be oriented perpendicular to gravity. A plurality of substrates may be defined by a number N, where N is greater than five. The plurality of substrates may include five or more separate substrates. In another embodiment, the plurality of substrates can include 40 or more separate substrates. For example, each substrate may have a size of about 65 cm x 165 cm. Each substrate is held in a substantially planar configuration with no warpage or damage. For example, if the substrate is placed in a direction other than a direction perpendicular to gravity, gravity causes the substrate to sag and warp. This occurs when the substrate material reaches a softening temperature, jeopardizing the structural integrity of the substrate. Typically, glass substrates, especially soda lime glass substrates, begin to soften at 480 ° C (commonly referred to as strain point). In one embodiment, the substrates are also isolated from each other according to a predetermined interval to ensure uniform heating and reaction with gaseous species to be introduced into the furnace.

After positioning the substrate in the processing chamber, in step 406 , gaseous species (including hydrogen species, selenium species, and/or carrier gas) are introduced into the processing chamber. In one embodiment, the gaseous species comprise at least a selenide species (eg, H ₂ Se) and nitrogen. In another embodiment, the gaseous species include other types of chemically inert gases such as helium, argon, and the like. For example, the substrate is placed in a gas containing selenium (for example, H ₂ Se).

Then, in step 408 , the furnace is heated to a second temperature in the range of from about 350 °C to 450 °C. In order to heat the processing chamber, thermal energy transfer can be achieved by heating elements, heating coils, and the like. For example, in step 408 , at least a copper indium diselenide film is formed by a reaction between a gaseous species and a composite (or layered) structure of copper and indium on each substrate. In a specific embodiment, separate layers of copper and indium materials diffuse into each other to form a single layer of copper indium alloy material. In step 410 , the second temperature is maintained between 350 ° C and 450 ° C for about 10 to 60 minutes (time period) during the heat treatment interval. In another embodiment, the second temperature can range from 390 °C to 410 °C. For example, the period of time provided by step 410 for maintaining the temperature enables the formation of a CIS film material. As the temperature increases, the pressure inside the furnace also increases. In a specific embodiment, the pressure inside the furnace is maintained at about 650 Torr with a pressure relief valve.

In one embodiment, the hydrogen selenide H ₂ Se is partially thermally cracked into H atoms and Se vapors during a temperature ramping from a first temperature to a second temperature and at a second temperature. The Se vapor can be partially removed in one or more processes. For example, a cryopump can be installed to extract Se vapor directly from the chamber. In another embodiment, the cooled end cap can function as a cryopump to absorb or condense Se vapor or Se clusters carried by convection from the hot chamber processing zone to the cooled end cap region, effectively extracting Selenium substance.

During the temperature maintenance process (step 410 ), in step 412 , additional removal of residual selenide species begins. In step 414 , a vacuum is created in the processing chamber by a vacuum pump. In a specific embodiment, the residual selenide removal process can continue until the process chamber as suggested in the above paragraph is in a vacuum configuration. In step 416, once the vacuum is generated (step 414) in the processing chamber, on the introduction of hydrogen sulfide (H ₂ S) material. The introduced H ₂ S at the second temperature stabilization level causes an exchange reaction with the selenium species contained in the copper indium composite film. For example, the following reaction occurs, CuInSe ₂ + H ₂ S → CuInSe _x S _1-x + H ₂ Se, Se is partially removed from the film on the substrate, and H ₂ Se is regenerated in the environment inside the chamber. At the same time, Se particles or fines can be continuously transported by convection from the thermal reaction chamber to a cooler region including the end cap region such that it can be deposited on the end cap surface, keeping the reaction chamber substantially free of elemental selenium. After the gas environment in the furnace has been changed such that the selenide material is removed and the hydrogen sulfide species is introduced, a second temperature climb process is initiated, step 418 . In a specific embodiment, nitrogen gas that acts as a carrier gas is introduced with the selenide species. The temperature of the furnace is raised to a third temperature ranging from about 500 °C to 525 °C. For example, the third temperature is calibrated in order to react between the hydrogen sulfide species in the furnace and the substrate. In one preferred embodiment, since the metal end cap 304 has a higher thermal conductivity, a metal end cap 304 is much faster than a quartz process chamber 302 to cool. The metal end cap 304 can remain "cooled" (substantially below 200 °C) even when the chamber tube 302 is hot. A temperature gradient is created which creates convection within the internal processing region 320 . As a result, selenium and/or other residues accumulate and deposit on the end cap. In a specific embodiment, the furnace 300 as described above has a separately controllable heating unit for maintaining temperature uniformity within the furnace. For example, these heaters can also be used to create a temperature differential that causes selenium and/or other residues to move to the end cap region.

At step 420 , the temperature is maintained at the third temperature for a certain period of time until the formation of the CIS layer is completed. The retention time at this interval in the environment of the furnace including the sulfur substance is set for the purpose of extracting one or more selenium substances from the copper indium diselenide film. It is beneficial to remove a predetermined amount of selenium species. In a specific embodiment, about 5% selenium is removed from the membrane and replaced with about 5% sulfur. According to one embodiment, it is desirable to carry out a complete reaction between the selenium material and the CIS membrane. In step 422 , after the selenium species is removed, a controlled temperature ramp down process begins. In step 424 , the furnace is cooled to a first temperature of about room temperature and the remaining gaseous species are removed from the furnace. For example, a vacuum pump is used to remove gaseous species. The above temperature sequence can be shown in the temperature distribution in FIG.

In step 420 , after decomposing the residual selenide species, a temperature ramp down process is initiated. The furnace is cooled to a first temperature of about room temperature and the remaining gaseous material is removed from the furnace. In a specific embodiment, the end cap material of the furnace is made of a material that cools faster than the quartz tube of the processing chamber. As a result, a gas flow is generated in the furnace toward the end cap (lower temperature), causing residue to deposit on the end cap. In one embodiment, the gaseous material is removed using a vacuum pump. The above temperature sequence can be shown in the temperature distribution in FIG.

After step 422 , a final cleaning process is performed to remove various residues deposited on the furnace end cap. Depending on the conditions, the residue can be removed by simply wiping the end cap, scratching, polishing, and/or other methods. It should be understood that cleaning the end cap that can be easily removed from the furnace is much more convenient than cleaning the interior of the processing chamber.

Other steps can also be performed depending on the desired end product. For example, if a thin film solar cell of the CIS or CIGS type is desired, additional processing is provided to provide additional structures, such as a layer of transparent material, such as ZnO overlying the CIS layer.

It is also to be understood that the embodiments and the embodiments described herein are for illustrative purposes only and that various modifications and changes may be made by those skilled in the art that are included in the present application. Spirit and scope and the scope of the attached patent application.

5 and 5A are diagrams of temperature distribution of a furnace in accordance with an embodiment of the present invention. These figures are only one example and should not limit the scope of the patent application herein. The temperature distribution further details the outline of the above method (Fig. 4) and the temperature gradient change process in the specification. An optimum temperature distribution (Figs. 5 and 5A) is provided to illustrate the heat treatment in accordance with an embodiment of the present invention. This optimal distribution adjusts the processing chamber to prevent thermal gradients and warpage of large substrates at high temperatures. If the temperature climbs too high and too fast, warping or damage may occur due to softening of the glass. In addition, the total amount of heat stored by the substrate is considered to determine the total amount of thermal energy and to maintain the uniformity and structural integrity of the glass substrate. For example, by periodically controlling the temperature of the heat treatment in multiple steps, the substrate is maintained at a certain level of stability and relaxation and maintains the necessary structural integrity. As explained above, materials such as glass tend to deform at temperatures of 480 ° C or higher, so care should be taken to avoid prolonging the exposure of the substrate to elevated temperatures. Referring to FIG. 5, a plurality of substrates are placed in a furnace while maintaining a processing chamber environment with a gaseous substance including a selenide substance and a carrier gas. In one embodiment, the air in the processing chamber is withdrawn prior to filling the gaseous material into the processing chamber. In an exemplary embodiment, the carrier gas comprises nitrogen. For example, the gaseous material fills the processing chamber to a pressure of about 650 Torr. A plurality of substrates are vertically oriented with respect to the direction of gravity, and a plurality of substrates are defined by a number N, where N is greater than five. In one embodiment, the substrate comprises a glass substrate, such as soda lime glass. The furnace is at a first temperature below 100 °C. The furnace is then heated to a second temperature in the range of from about 350 °C to 450 °C.

In the heat treatment interval, the second temperature is maintained between 350 ° C and 450 ° C for about 10 to 60 minutes (time period). The size of the glass substrate may be, but is not limited to, 65 cm x 165 cm. One challenge in handling such large substrates is the warpage of the substrate at high temperatures. If the temperature is raised directly to T3, warpage or damage will occur. As shown, the slope from T2 to T3 is calibrated to reduce and/or eliminate the risk of damage to the substrate. In one embodiment, as shown in Figure 5A, a portion of the selenide gas is removed as the temperature climbs from T2 to T3. The substrate is relaxed and stabilized by maintaining the temperature in the processing chamber at T2 for a period of time. The retention time at this interval is set in accordance with the purpose of at least initially forming a copper indium diselenide film from the copper and indium composite structures on each of the substrates.

The furnace is then cooled to a third temperature ranging from 500 °C to room temperature. During the selenization process, residual selenide species will collect in the internal processing zone 320 previously shown in FIG. At elevated temperatures, the selenide species remains in vapor form within the internal processing zone 320 . As the temperature decreases, the selenide material deposits on the colder surface. In a preferred embodiment, the uninsulated metal end cap 304 cools much faster than the quartz processing chamber 302 due to its higher thermal conductivity. A temperature gradient is created which creates convection within the internal processing region 320 . Convection causes elemental selenium to flow toward the end cap 304 and deposit on the cooler end cap region 322 . By this method, the internal treatment zone 320 can be maintained substantially free of elemental selenium species by decomposing residual selenide species in the interior region of the treatment zone.

After the environment in the furnace has been altered such that any residual selenide species is decomposed and deposited at the end cap region 322 , an additional step can be introduced depending on the process of forming the CIS layer on the surface of the substrate. In another embodiment, an additional temperature gradient change and retention step can be used to form the CIS film to prevent the substrate from warping or becoming damaged.

After the formation of the CIS layer, a temperature ramp down process is initiated and the furnace is then cooled to a first temperature of about room temperature. According to one embodiment, the cooling process is specifically calibrated. As a result of this treatment, copper, indium, and selenium diffuse and react with each other to form a high-quality copper indium diselenide film. In one embodiment, a gaseous substance such as nitrogen is used during the cooling process.

6A is a simplified diagram of a thin film copper indium diselenide device in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, structure 600 is supported on glass substrate 610 . According to one embodiment, the glass substrate comprises soda lime glass having a thickness of about 1 to 3 mm. A back contact including a metal layer 608 is deposited on the substrate 610 . According to one embodiment, layer 608 primarily comprises a molybdenum film deposited by sputtering. The first active region of structure 600 includes a semiconductor layer 606 . In one embodiment, the semiconductor layer comprises a p-type copper indium diselenide (CIS) material characterized by an overall thickness of 500 to 1500 μm. It should be understood that other semiconductor layers may include other types of materials, such as CIGS. The second active portion of structure 600 includes layers 604 and 602 of an n-type semiconductor material, such as CdS or ZnO. FIG. 6A illustrates a second active portion of structure 600 including two CdS layers 602 and 604 having different levels of resistivity. Another embodiment is illustrated in Figure 6B, wherein the second active portion of the structure comprises a CdS layer and a ZnO layer.

6B is a simplified diagram of a thin film copper indium diselenide device in accordance with another embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, the structure 620 is supported on a glass substrate 630 . According to one embodiment, the glass substrate comprises soda lime glass having a thickness of about 1 to 3 mm. A back contact comprising a metal layer 628 is deposited on the substrate 630 . According to one embodiment, layer 628 primarily comprises a molybdenum film deposited by sputtering. The first active region of structure 620 includes a semiconductor layer 626 . In one embodiment, the semiconductor layer comprises a p-type copper indium diselenide (CIS) material. It should be understood that other semiconductor layers may include other types of materials, such as CIGS. The second active portion of structure 620 includes layers CdS 624 and ZnO 622 of n-type semiconductor material.

A photovoltaic cell or solar cell (eg, device 600 described above) is constructed as a large area pn junction. When photons in the sun strike the photovoltaic cell, the photons are reflected through the transparent electrode layer or absorbed. The semiconductor layer absorbs energy that causes the generation of electron-hole pairs. Photons need to have more energy than the band gap to excite electrons from the valence band into the conduction band. This allows electrons to flow through the material to generate electricity. Complementary positive charges or holes flow in a direction opposite to the electrons in the photovoltaic cell. Solar panels with many photovoltaic cells convert solar energy into direct current.

For thin film solar cell applications, semiconductors based on copper indium diselenide (CIS) construction are particularly attractive due to their high optical absorption coefficient and general optoelectronic properties. In principle, these characteristics can be manipulated and adjusted for specific needs in a given device. Selenium enables better uniformity of the entire layer and thereby reduces the number of recombination sites in the film, which facilitates improved quantum efficiency and thereby improved conversion efficiency.

The present invention provides a method of fabricating a CIS-based and/or CIGS-based solar cell on a large glass substrate for a solar panel. The device structures depicted in Figure 6 can be patterned to form individual solar cells on a glass substrate and connected to each other to form a solar panel. Accordingly, the present invention provides a cost effective method of fabricating thin film solar panels.

It should be understood that all of the benefits of the present invention can be achieved regardless of the order of deposition of the copper and indium films. That is, indium may be deposited first, or the film may be deposited as a sandwich or a thinner plurality of layers of the stack.

It is also to be understood that the embodiments and embodiments described herein are for illustrative purposes only, and that there are various modifications or variations that may be made by those skilled in the art, which are included in the present application. Spirit and scope and the scope of the attached patent application.

7 is a simplified diagram of a self-cleaning furnace prior to decomposition of a selenide material, in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, furnace 700 includes a process chamber 702 and an end cap 704 for the chamber. The inner surface and the spatial region of the process chamber 702 are depicted as an inner processing region 706 . In one embodiment, the processing chamber 702 can include a quartz tube. End cap region 708 represents the inner surface of end cap 704 that is exposed to inner processing region 706 . As noted above, end cap 704 and processing chamber 702 are characterized by surface reactivity and/or viscosity differences for various types of gaseous materials. For example, under certain conditions, various types of materials may be deposited on the end cap 704 , but not on the inner surface of the chamber 702 . In a specific embodiment, the end cap region 702 is made of a material having a lower specific heat than the processing chamber 702 . In one embodiment, the end cap 704 is composed of at least a metallic material. Residual selenide 710 may be deposited in internal processing region 706 during the selenization process. According to one embodiment, the temperature gradient can be formed by introducing a mechanical baffle between the inner treatment zone and the end cap region such that convection can carry the residue away from the inner treatment zone and prevent residual selenide 710 from being deposited internally. In area 706 .

It is also to be understood that the embodiments and embodiments described herein are for illustrative purposes only, and that there are various modifications or variations that may be made by those skilled in the art, which are included in the present application. Spirit and scope and the scope of the attached patent application.

Figure 8A is a simplified diagram of a self-cleaning furnace prior to decomposition of a selenide material, in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, furnace 800 includes a process chamber 802 and an end cap 804 for the chamber. The inner surface and spatial area of the processing chamber 802 are depicted as internal processing regions 806 . In one embodiment, the processing chamber 802 can include a quartz tube. End cap region 808 represents the inner surface of end cap 804 that is exposed to inner processing region 806 . In one embodiment, the end cap 804 can be made of a metallic material. Residual selenide 810 may have been deposited in internal processing region 806 during the selenization process. According to one embodiment, a temperature gradient can be formed by introducing a mechanical baffle between the inner processing region 806 and the end cap region 808 such that convection can carry residual particles away from the inner processing region and substantially prevent residual selenide 810 Deposited in internal processing region 806 .

8B is a simplified diagram of a self-cleaning furnace during the decomposition of selenide species and the deposition of elemental selenium at the end caps, in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, furnace 820 includes a processing chamber 822 and an end cap 824 of the chamber. The inner surface and the spatial region of the processing chamber 822 are depicted as internal processing regions 826 . In one embodiment, the processing chamber 822 can include a quartz tube. End cap region 828 represents the inner surface of end cap 824 that is exposed to inner processing region 826 . In one embodiment, the end cap 824 can be made of a metallic material. During the decomposition of the selenide species, residual material 830 , including elemental selenium, is vaporized and carried (by convection carried by the thermal gradient) from internal processing region 826 toward end cap region 824 .

8C is a simplified diagram of a self-cleaning furnace after decomposition of a selenide species and deposition of elemental selenium at an end cap, in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, furnace 840 includes a process chamber 842 and an end cap 844 for the chamber. The inner surface and the spatial region of the processing chamber 842 are depicted as an inner processing region 846 . In one embodiment, the processing chamber 842 can include a quartz tube. End cap region 848 represents the inner surface of end cap 844 that is exposed to inner processing region 846 . In one embodiment, the end cap 844 can be made of a metallic material. Residual selenide 850 is included in end cap region 848 after decomposition and deposition of the selenide species. For example, due to the temperature gradient between the end cap and the processing chamber, deposition or condensation of residual selenide 810 is caused, at least in part, by convection. The temperature gradient can be greatly enhanced by the addition of a baffle structure that acts as a controllable permeable barrier. After the formation of the CIS layer is completed and the substrate is removed from the processing chamber 842 , the residual selenide can be mechanically removed with a cloth (eg, linen, or the like). It will be appreciated that by allowing selenide and/or other residues to accumulate on the end cap structure, the cleaning process can be facilitated and the residue on the end cap structure can be easily wiped off. In various conventional techniques, cleaning the residue from the furnace typically requires cleaning the interior of the processing chamber.

8A, 8B, and 8C are diagrams showing the steps of decomposition of residual selenide and a path when elemental selenium is deposited at the end cap region of the processing chamber.

It should also be understood that the examples and embodiments described herein are for illustrative purposes only and that there are various modifications or variations that are apparent to those skilled in the art that are included in the spirit of the present application. And scope and the scope of the appended patent application.

9 is a simplified diagram of a self-cleaning furnace after decomposition of a selenide species and deposition of elemental selenium at an end cap, in accordance with an embodiment of the present invention. This figure is only an example and should not limit the scope of the patent application herein. As shown, furnace 900 includes a process chamber 902 and an end cap 904 for the chamber. The inner surface and the spatial region of the processing chamber 902 are depicted as an inner processing region 906 . In one embodiment, the processing chamber 902 can include a quartz tube. End cap region 908 represents the inner surface of end cap 904 that is exposed to inner processing region 906 . In one embodiment, the end cap 904 can be made of a metallic material. Residual selenide 910 is included in end cap region 908 after decomposition and deposition of the selenide species. After the formation of the CIS layer is completed and the substrate is removed from the processing chamber 902 , a cloth such as linen, or the like, may be used to mechanically remove residual selenide.

It is also to be understood that the embodiments and the embodiments described herein are for the purpose of illustrations And scope and the scope of the appended patent application. Although specific structures for CIS and/or CIGS thin film batteries have been primarily described above, other specific CIS and/or CIGS configurations may be used without departing from the invention described by the scope of the present application. , for example, those mentioned in the U.S. Patent Nos. 4,611,091 and 4,612,411, the disclosures of each of which are incorporated herein by reference.

100. . . Processing structure, structure

102. . . Metal electrode layer

104. . . Transparent substrate, substrate

200. . . structure

202. . . Floor

204. . . Floor

206. . . Depositing metal layers, metal layers, layers

208. . . Glass, glass substrate, substrate

210. . . Composite structure, structure, substrate

212. . . Floor

214. . . Metal electrode layer

216. . . Transparent substrate, glass, substrate

300. . . furnace

302. . . Processing room

304. . . End cap

306. . . Heating element

308. . . Substrate

310. . . Turbomolecular pump

312. . . Rotary pump

314. . . Gas injection pipeline

316. . . Manifold

318. . . Conduction valve

400. . . method

402. . . step

404. . . step

406. . . step

408. . . step

410. . . step

412. . . step

414. . . step

416. . . step

418. . . step

420. . . step

422. . . step

424. . . step

426. . . step

428. . . step

600. . . supporting structure

602. . . Floor

604. . . Floor

606. . . Semiconductor layer

608. . . Metal layer

610. . . Substrate

620. . . structure

622. . . ZnO

624. . . Layer CdS

626. . . Semiconductor layer

628. . . Floor

630. . . glass substrate

700. . . furnace

702. . . Processing room

704. . . End cap

706. . . Internal processing area

708. . . End cap area

710. . . Selenide

800. . . furnace

802. . . Processing room

804. . . End cap

806. . . Internal processing area

808. . . End cap area

810. . . Selenide

820. . . furnace

822. . . Processing room

824. . . End cap

826. . . Internal processing area

828. . . End cap area

830. . . Residual substance

840. . . furnace

842. . . Processing room

844. . . End cap

846. . . Internal processing area

848. . . End cap area

850. . . Selenide

900. . . furnace

902. . . Processing room

904. . . End cap

906. . . Internal processing area

908. . . End cap area

910. . . Selenide

1 is a simplified diagram of a transparent substrate having overlapping electrode layers in accordance with an embodiment of the present invention;

2 is a simplified diagram of a composite structure including a copper and an indium film in accordance with an embodiment of the present invention;

2A is a simplified diagram of a composite structure including a copper indium composite/alloy according to an embodiment of the present invention;

Figure 3 is a schematic view of a furnace in accordance with an embodiment of the present invention;

4 is a simplified diagram of a process for forming a copper indium diselenide layer in accordance with an embodiment of the present invention;

5 and 5A are diagrams showing a temperature distribution of a furnace according to an embodiment of the present invention;

6A is a schematic diagram of a thin film copper indium diselenide device in accordance with an embodiment of the present invention;

6B is a schematic diagram of a thin film copper indium diselenide device in accordance with another embodiment of the present invention;

7 is a simplified diagram of a self-cleaning furnace prior to decomposition of a selenide material, in accordance with an embodiment of the present invention;

8A is a simplified diagram of a self-cleaning furnace prior to decomposition of a selenide material, in accordance with an embodiment of the present invention;

8B is a simplified diagram of a self-cleaning furnace during decomposition of a selenide species and deposition of elemental selenium at an end cap, in accordance with an embodiment of the present invention;

8C is a simplified diagram of a self-cleaning furnace after decomposition of a selenide species and deposition of elemental selenium at an end cap, in accordance with an embodiment of the present invention;

9 is a simplified diagram of a self-cleaning furnace after decomposition of a selenide species and deposition of elemental selenium at an end cap, in accordance with an embodiment of the present invention.

400. . . method

402. . . step

404. . . step

406. . . step

408. . . step

410. . . step

412. . . step

414. . . step

416. . . step

418. . . step

420. . . step

422. . . step

424. . . step

426. . . step

428. . . step

Claims (20)

A method of fabricating a copper indium diselenide semiconductor film using a self-cleaning furnace, comprising: transferring a plurality of substrates into a furnace, the furnace including a processing region and at least one end cap region detachably engaged with the processing region, Each of the plurality of substrates is disposed perpendicularly with respect to a direction of gravity, the plurality of substrates being defined by a number N, wherein N is greater than 5, each substrate having a composite structure of copper and indium; comprising hydrogen species and selenide A gaseous substance of a substance and a carrier gas is introduced into the furnace, and thermal energy is transferred to the furnace to raise the temperature from a first temperature to a second temperature, the second temperature ranging from about 350 ° C to At about 450 ° C, thereby forming a copper indium diselenide film from at least a copper and indium composite structure on each of the substrates; decomposing residual selenide material in an inner region of the processing region of the furnace; Depositing elemental selenium species in the vicinity of the end cap region operated at the third temperature; and maintaining the inner region by decomposing at least residual selenide species in the inner region of the treated region Substantially free of elemental selenium species. The method of claim 1, wherein in the process of depositing the elemental selenium material, the vicinity of the end cap region is characterized by a temperature lower than a temperature of the furnace chamber. The method of claim 1, wherein the end cap region is characterized by a specific heat lower than a specific heat of the furnace chamber. The method of claim 1, wherein depositing the elemental selenium material comprises cooling the furnace by a predetermined amount. The method of claim 1, further comprising removing deposited selenium species from the end cap region. The method of claim 1, wherein the substrate comprises a gallium material. The method of claim 1, wherein the second temperature ranges from about 390 ° C to about 410 ° C. The method of claim 1, wherein the first temperature is about room temperature. The method of claim 1, wherein the second temperature is maintained for about 10 to 60 minutes. The method of claim 1, wherein the gaseous substance comprises H ₂ Se. The method of claim 1, wherein the carrier gas comprises nitrogen. The method of claim 1, wherein N is greater than 40. The method of claim 1, wherein the furnace is characterized by a temperature distribution in the furnace having a uniformity of less than about 10 °C. The method of claim 1, wherein each of the substrates maintains a substantially planar configuration without warping or damage. The method of claim 1, wherein the furnace is characterized by a volume of 200 liters or more. The method of claim 1, wherein the processing region of the furnace comprises a quartz material. The method of claim 1, wherein the third temperature is lower than the second temperature. The method of claim 1, wherein the third temperature ranges from about 500 ° C to about 550 ° C. The method of claim 1, wherein the end cap region comprises a metallic material. The method of claim 1, further comprising removing a portion of the end cap region and mechanically removing the elemental selenium material to clean the furnace.