Preparation device and preparation method of efficient ultrathin CIGS solar cell absorption layer

Abstract

The invention discloses a preparation device and a preparation method of an efficient ultrathin CIGS solar cell absorption layer, and belongs to the technical field of solar cells, the device mainly comprises a process cavity, evaporation sources and an H2S gas inlet system, the process cavity comprises a preheating cavity, four evaporation cavities and a cooling cavity; the evaporation sources comprise a Se evaporation source, an alkali metal evaporation source, a first Ga evaporation source, a first In evaporation source, a Cu evaporation source, a second Ga evaporation source and a second In evaporation source, and the H2S gas inlet system is communicated with the fourth evaporation cavity. The preparation method comprises the following steps: respectively evaporating Ga, In and Cu in different chambers in Se and alkali metal atmosphere in three steps by utilizing the preparation device, enabling alkali metal to be uniformly doped into the absorption layer, co-evaporating, compensating and depositing Ga and In in a fourth evaporation cavity in H2S atmosphere, carrying out surface vulcanization on the absorption layer, and enabling Cu (In0. 5Ga0. 5) Se2 small crystal grains to exist on the surface of the absorption layer at low temperature, the surface roughness of the absorption layer is increased, and the electrical property parameters of the battery are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and specifically discloses a device and a method for preparing a high-efficiency ultra-thin CIGS solar cell absorption layer. Background Art

[0002] Copper indium gallium selenide (CIGS) thin film solar cells have high sunlight absorption efficiency, adjustable bandgap width, low cost, and good weak light performance. They are considered to be the most promising thin film solar cells. The cell structure is mainly composed of soda-lime glass / back electrode layer / absorption layer / buffer layer / window layer / transparent conductive layer. However, since the indium (In) (currently the world's production is 900 tons / year) and gallium (Ga) (currently the world's production is 300 tons / year) used to prepare the CIGS absorption layer film are rare elements, the global production is limited and the price is high, which has become a key factor restricting the development of CIGS solar cells. Fortunately, CIGS thin film has a high light absorption coefficient, which can reach up to 10 5 cm -1 By utilizing this feature, the thickness of the CIGS absorption layer can be reduced from the conventional 1.5-2.5μm to below 1μm, so the development of high-efficiency ultra-thin CIGS solar cells is crucial. The existing technology directly thins the absorption layer without changing the various technical parameters, which will greatly reduce the carrier concentration of the battery and affect the various performance parameters of the battery, and cannot meet the performance requirements of industrialized, large-area CIGS solar cells. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the carrier concentration of the solar cell is greatly reduced and various performance parameters of the cell are affected by directly thinning the absorption layer in the prior art, and to propose a preparation device and method for the absorption layer of a high-efficiency ultra-thin CIGS solar cell.

[0004] In order to solve the above technical problems, the present invention provides a device for preparing an efficient ultra-thin CIGS solar cell absorption layer, comprising:

[0005] The process chamber comprises a preheating chamber, an evaporation chamber and a cooling chamber which are arranged in sequence, wherein the evaporation chamber comprises a first evaporation chamber, a second evaporation chamber, a third evaporation chamber and a fourth evaporation chamber which are arranged in sequence;

[0006] A transmission system, arranged at the bottom of the process chamber, for transmitting the substrate;

[0007] A vacuum system, which is in communication with the process chamber and is used to provide vacuum for the process chamber;

[0008] The cavity heating resistance wire is arranged in the preheating cavity and the evaporation cavity, and is used for heating the preheating cavity and the evaporation cavity;

[0009] A cooling system is arranged in the cooling chamber;

[0010] An evaporation source, including an alkali metal evaporation source, a selenium evaporation source, a first Ga evaporation source, a first In evaporation source, a Cu evaporation source, a second Ga evaporation source, and a second In evaporation source, wherein the evaporation source is provided with an evaporation source heating resistance wire, and the evaporation source is communicated with an evaporation chamber through a connecting pipe, wherein the alkali metal evaporation source and the Se evaporation source are communicated with all evaporation chambers, the first Ga evaporation source is communicated with the first evaporation chamber, the first In evaporation source is communicated with the second evaporation chamber, the Cu evaporation source is communicated with the third evaporation chamber, and the second Ga evaporation source and the second In evaporation source are both communicated with the fourth evaporation chamber;

[0011] H 2 S air intake system, communicating with the fourth evaporation chamber;

[0012] The temperature control system is arranged in the preheating chamber, the evaporation chamber and the cooling chamber, and is used to control the temperature of the preheating chamber, the evaporation chamber and the cooling chamber.

[0013] As a further description of the present invention, an entrance door is provided at the entrance of the preheating chamber, an exit door is provided at the exit of the cooling chamber, and isolation doors are provided between the preheating chamber, the first evaporation chamber, the second evaporation chamber, the third evaporation chamber, the fourth evaporation chamber and the cooling chamber.

[0014] As a further description of the present invention, position sensors are provided on the chamber entrance door, the isolation door and the chamber exit door.

[0015] As a further description of the present invention, an evaporation source heating resistance wire is provided in each of the evaporation sources.

[0016] As a further description of the present invention, a control valve is provided on the connecting pipeline.

[0017] As a further description of the present invention, a pipeline heating device is provided on the connecting pipeline.

[0018] In order to solve the above technical problems, the present invention also provides a method for preparing a high-efficiency ultra-thin CIGS solar cell absorption layer, comprising the following steps:

[0019] (1) Turn on the vacuum system and evacuate the preheating chamber and evaporation chamber to a vacuum degree of 3.0×10 -6 mbar; turn on the heating resistor wire to control the temperature in the preheating chamber and the evaporation chamber at 340-360°C, turn on the evaporation source heating wire to make all evaporation sources reach the predetermined evaporation temperature, turn on the alkali metal evaporation source and the Se evaporation source to fill the process chamber with Se and alkali metal vapor, of which the alkali metal vapor accounts for 0.08-0.1%;

[0020] (2) sending the substrate into a preheating chamber for preheating;

[0021] (3) transferring the preheated substrate to the first evaporation chamber, and co-evaporating and depositing Ga on the back electrode at a Ga deposition rate of 30 to 50 nm / min for 3 to 5 min;

[0022] (4) Transferring to the second evaporation chamber, co-evaporating and depositing In, the In deposition rate is 30-50 nm / min, and the time is 3-5 min;

[0023] (5) transferring to the third evaporation chamber to co-evaporate and deposit Cu at a Cu deposition rate of 50 to 70 nm / min for 4 to 6 min;

[0024] (6) is transferred to the fourth evaporation chamber, and 2 Ga and In were deposited by co-evaporation compensation in S atmosphere, with a compensation deposition rate of 30-50 nm / min and a time of 1-2 min;

[0025] (7) The product is transferred to a cooling chamber for cooling, thereby completing the preparation of the CIGS solar cell absorption layer.

[0026] As a further description of the present invention, the alkali metal evaporation source is preferably Na / Na 2 S evaporation source.

[0027] As a further description of the present invention, after the Cu is evaporated and deposited in step (5), it is necessary to detect whether the deposited film is rich in Cu. The film is then sent to the fourth chamber after it is rich in Cu.

[0028] As a further description of the present invention, the atomic fraction ratio of Cu:In:Ga:Se in step (6) is (28-35):(8-15):(4-7):(40-55).

[0029] The method of the present invention utilizes a preparation device for the absorption layer, and controls the temperature of the substrate at a low temperature of 340 to 360° C. through a precise temperature control system. In a Se atmosphere, the element Ga is first evaporated, and after evaporation for a certain period of time, the substrate is transferred to the next chamber to evaporate In, and after obtaining a suitable element ratio, it is transferred to the next chamber to evaporate Cu, and a method of checking the cooling point is used to determine whether the film is Cu-rich. After the film is Cu-rich, indium and gallium are added to adjust the film composition. During the reaction process, Na, K or other alkali metal compounds are continuously evaporated into the evaporation chamber to allow the alkali metal to be uniformly incorporated into the absorption layer, and finally H is introduced into the fourth evaporation chamber. 2 S, the surface of the absorption layer is sulfurized, and the Ga / (Ga+In) of the final absorption layer is about 0.30, Cu / (Ga+In) is about 0.91, and the thickness is about 0.70μm. At low temperature, there is Cu(In 0.5 Ga 0.5 )Se2 Small grains increase the roughness of the absorption layer surface, and the alkali metal is evenly distributed in the absorption layer while the surface sulfidation degree is improved, which can also greatly improve the electrical performance parameters of the battery.

[0030] In order to solve the above technical problems, the present invention also provides a method for preparing a high-efficiency ultra-thin CIGS solar cell. The absorption layer of the high-efficiency ultra-thin CIGS solar cell is prepared by the above method, and a light trapping structure is formed at the CdS / CIGS interface. At the same time, a low-Ga-containing phase and a high-Ga-containing phase are separated at low temperatures. The band gap value of the low-Ga-containing phase is small, which is conducive to the absorption of long-wave light and greatly improves JSC (short circuit current);

[0031] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0032] (1) During the CIGS co-evaporation process, the substrate temperature and evaporation time are precisely controlled to ensure that Cu(In 0.5 Ga 0.5 )Se 2 Small grains increase the surface roughness of the absorption layer, forming a light-trapping structure at the CdS / CIGS interface. At the same time, at low temperatures, there is a separation between the low-Ga-containing phase and the high-Ga-containing phase. The band gap value of the low-Ga-containing phase is small, which is conducive to the absorption of long-wave light and effectively improves JSC. The conversion efficiency of the high-efficiency ultra-thin CIGS solar cell with a thickness of about 0.7μm prepared at a substrate temperature of 350℃ reached 15%, achieving the goals of low temperature, ultra-thinness and high efficiency.

[0033] (2) Alkali metal elements are uniformly introduced during the formation of the absorption layer, which effectively improves the electrical properties of the absorption layer; the S element is introduced in the final stage of the reaction to increase the S content on the surface of the absorption layer. At the same time, Ga forms a "V"-shaped gradient band gap during the entire evaporation process. The silver nanowire array can effectively improve the conductivity and light transmittance of the transparent conductive film, effectively improve the collection capacity of photogenerated carriers, and further increase the conversion efficiency of the battery;

[0034] (3) The continuous and rapid preparation method of the absorption layer can be applied to large-scale, large-size and continuous production, and has a wide range of applications;

[0035] (4) By combining the absorption layer preparation device with effective parameter control, the absorption layer thickness and performance can be optimized, the absorption layer performance can be continuously improved, and thus the various performances of CIGS solar cells can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of a device for preparing a high-efficiency ultra-thin CIGS solar cell according to the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of a high-efficiency ultra-thin CIGS solar cell prepared by the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] Embodiment 1:

[0040] This embodiment provides a device for preparing an efficient ultra-thin CIGS solar cell absorption layer. Figure 1 As shown, including:

[0041] A process chamber, comprising a preheating chamber 110, an evaporation chamber and a cooling chamber 130 which are arranged in sequence, wherein the evaporation chamber comprises a first evaporation chamber 121, a second evaporation chamber 122, a third evaporation chamber 123 and a fourth evaporation chamber 124 which are arranged in sequence, an inlet door 141 is arranged at the entrance of the preheating chamber 110, an outlet door 143 is arranged at the exit of the cooling chamber 130, an isolation door 142 is arranged between the preheating chamber 110, the first evaporation chamber 121, the second evaporation chamber 122, the third evaporation chamber 123, the fourth evaporation chamber 124 and the cooling chamber 130, and position sensors 144 are arranged on the inlet door 141 and the isolation door 142;

[0042] The transport system 200 includes a transport roller disposed at the bottom of the process chamber and used for transporting the substrate;

[0043] A vacuum system 300 is communicated with the process chamber and is used to provide vacuum for the process chamber;

[0044] The cavity heating resistance wire 400 is arranged in the preheating cavity 110 and the evaporation cavity, and is used to heat the preheating cavity 110 and the evaporation cavity;

[0045] A cooling fan 500 is disposed in the cooling chamber 130;

[0046] Evaporation source, wherein the evaporation source is provided with an evaporation source heating resistor 680, the evaporation source is connected to the evaporation chamber through a connecting pipe, and a control valve and a pipe heating device 690 are provided on the connecting pipe. The evaporation source includes Na / Na 2 S evaporation source 610, Se evaporation source 620, first Ga evaporation source 630, first In evaporation source 640, Cu evaporation source 650, second Ga evaporation source 660 and second In evaporation source 670, wherein Na / Na 2 The S evaporation source 610 and the Se evaporation source 620 are in communication with all the evaporation chambers, the first Ga evaporation source 630 is in communication with the first evaporation chamber 121, the first In evaporation source 640 is in communication with the second evaporation chamber 122, the Cu evaporation source 650 is in communication with the third evaporation chamber 123, and the second Ga evaporation source 660 and the second In evaporation source 670 are both in communication with the fourth evaporation chamber 123;

[0047] H 2 Se / H 2 S air intake system 700, communicating with the fourth evaporation chamber 123;

[0048] The temperature control system 800 is disposed in the preheating chamber 110 , the four evaporation chambers 121 , 122 , 123 , 124 and the cooling chamber 130 .

[0049] Embodiment 2:

[0050] This embodiment provides a method for preparing an efficient ultra-thin CIGS solar cell absorption layer, using the device of embodiment 1, comprising the following steps:

[0051] (1) Turn on the vacuum system 300 and evacuate the entire process chamber. The vacuum degree is required to reach 3.0×10 -6 mbar, turn on the chamber heating resistor 400 and the temperature control system 800, accurately control the temperature in the preheating chamber 110 and the evaporation chamber at 340-360°C, turn on the evaporation source heating resistor 680, make all evaporation sources reach the predetermined evaporation temperature, turn on the Na evaporation source 610 and the Se evaporation source 620, make the process chamber full of Se and Na vapor, of which the Na vapor accounts for 0.08-0.1%;

[0052] (2) Open the chamber door 141 and the transmission system 200, and send the glass substrate coated with the molybdenum back electrode into the preheating chamber 110 for heating, so that the substrate temperature reaches 340-360° C.;

[0053] (3) opening the isolation door 142 between the preheating chamber 110 and the first evaporation chamber 121, allowing the glass substrate to enter the first evaporation chamber 121, opening the control valve of the first Ga evaporation source 630, and co-evaporating and depositing Ga at a deposition rate of 30 to 50 nm / min for a deposition time of 3 to 5 min;

[0054] (4) Open the isolation door 142 between the first evaporation chamber 121 and the second evaporation chamber 122, the substrate enters the second evaporation chamber 122, open the control valve of the first In evaporation source 640, and co-evaporate and deposit In. The deposition rate of In is 30 to 50 nm / min, and the deposition time is 6 to 10 min;

[0055] (5) Open the isolation door 142 between the second evaporation chamber 121 and the third evaporation chamber 122, and the substrate enters the second evaporation chamber 122. Open the control valve of the Cu evaporation source 650, co-evaporate and deposit Cu, and use the method of checking the temperature drop point to detect whether the deposited film is Cu-rich. After the film is Cu-rich, it is transferred to the next chamber. The Cu deposition rate is 50-70 nm / min, and the deposition time is 4-6 min.

[0056] (6) The isolation door 142 between the third evaporation chamber 123 and the fourth evaporation chamber 124 is opened, and the substrate enters the fourth evaporation chamber 123. The temperature of the fourth evaporation chamber 123 is maintained at 380-420°C. At the same time, H 2 The control valves of the S intake system 700, the second Ga evaporation source 660 and the second In evaporation source 670 are arranged in the H 2 Co-evaporation compensation deposition of Ga and In in S atmosphere, the deposition rate is 30-50 nm / min, the deposition time is 1-2 min, and the final atomic fraction ratio of Cu: In: Ga: Se is (28-35): (8-15): (4-7): (40-55);

[0057] (7) The isolation door 142 between the third evaporation chamber 123 and the cooling chamber 130 is opened, the substrate enters the cooling chamber 130, and the cooling fan 500 is turned on to quickly cool the substrate, which is conducive to the formation of a chalcopyrite structure in the absorption layer, and finally forms an ultra-thin CIGS absorption layer with a Ga / (Ga+In) ratio of about 0.30, a Cu / (Ga+In) of about 0.91, a thickness of about 0.70 μm, and a surface sulfurization treatment.

[0058] Embodiment three:

[0059] This embodiment provides a method for preparing a high-efficiency ultra-thin CIGS solar cell. Figure 2 As shown, the following steps are included:

[0060] (1) a Mo (molybdenum) film, a SiN layer and a Mo film are sequentially deposited on a glass substrate 10 by magnetron sputtering to form a Mo back electrode 20;

[0061] (2) cleaning the substrate glass 10 with the Mo back electrode 20 to remove dirt;

[0062] (3) The CIGS absorption layer 30 is evaporated and deposited on the Mo back electrode 20 by the method of Example 2, and Na 31 and S 32 are uniformly added to the CIGS absorption layer;

[0063] (4) On the CIGS absorption layer 30, a CdS buffer layer of about 50 nm is prepared by a chemical bath method (CBD);

[0064] (5) using magnetron sputtering to prepare 80 nm of intrinsic ZnO and about 800 nm of low-resistance ZnO:Al window on the buffer layer 40 to form a buffer layer 40 with a window;

[0065] (6) A 900 nm AZO transparent conductive layer 50 is prepared on the buffer layer 40 by using a DC magnetron sputtering method;

[0066] (7) A silver nanowire array of a few nanometers is formed on the AZO transparent conductive layer 50 by a PVD method, and finally a high-efficiency ultra-thin CIGS solar cell is formed.

[0067] The high-efficiency ultra-thin CIGS solar cell prepared in this embodiment is as follows Figure 2 As shown, the thickness of the CIGS absorption layer 30 is only 0.7 μm, forming Cu(In 0.5 Ga 0.5 )Se 2 Small grains increase the surface roughness of the absorption layer. Na 31 and S 32 are evenly incorporated into the CIGS absorption layer 30, so as to achieve the purpose of thinning the CIGS absorption layer 30 without affecting the battery conversion efficiency. A light trapping structure is also formed at the CdS / CIGS interface. At the same time, a low-Ga-containing phase and a high-Ga-containing phase are separated at low temperatures. The band gap value of the low-Ga-containing phase is small, which is conducive to the absorption of long-wave light, effectively improving JSC. The conversion efficiency of CIGS solar cells reaches 15%.

[0068] The method of the present invention uses a low-temperature preparation device for preparing a CIGS solar cell absorption layer, uses a precise temperature control system, controls the temperature of the substrate at a low temperature of 340-360 DEG C, and continuously evaporates the elements of the absorption layer in sequence under a Se atmosphere. During the reaction process, Na, K or other alkali metal compounds are continuously evaporated into an evaporation chamber, so that the alkali metal is uniformly incorporated into the absorption layer, thereby achieving the purpose of thinning the absorption layer without affecting the battery conversion efficiency; at the same time, the S element is introduced in the last stage of evaporation, and a silver nanowire array is formed on a transparent conductive film by a PVD method, so as to further improve various performance parameters of the battery; finally, a high-efficiency CIGS solar cell absorption layer with a thickness of only 0.7 μm and a "V"-shaped gradient band gap is formed, the electron transmission is enhanced, the open circuit voltage and the filling factor are improved, thereby improving the photoelectric conversion efficiency of the CIGS solar cell, greatly reducing the production cost of the CIGS solar cell, and the process is stable, controllable and pollution-free.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. A person skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A device for preparing an efficient ultra-thin CIGS solar cell absorption layer, characterized in that: include: The process chamber comprises a preheating chamber, an evaporation chamber and a cooling chamber which are arranged in sequence, wherein the evaporation chamber comprises a first evaporation chamber, a second evaporation chamber, a third evaporation chamber and a fourth evaporation chamber which are arranged in sequence; A transmission system, arranged at the bottom of the process chamber, for transmitting the substrate; A vacuum system, which is in communication with the process chamber and is used to provide vacuum for the process chamber; The cavity heating resistance wire is arranged in the preheating cavity and the evaporation cavity, and is used for heating the preheating cavity and the evaporation cavity; A cooling system is arranged in the cooling chamber; An evaporation source, comprising an alkali metal evaporation source, a Se evaporation source, a first Ga evaporation source, a first In evaporation source, a Cu evaporation source, a second Ga evaporation source, and a second In evaporation source, wherein the evaporation source is provided with an evaporation source heating resistance wire, and the evaporation source is communicated with the evaporation chamber through a connecting pipe, wherein the alkali metal evaporation source and the Se evaporation source are communicated with all the evaporation chambers, the first Ga evaporation source is communicated with the first evaporation chamber, the first In evaporation source is communicated with the second evaporation chamber, the Cu evaporation source is communicated with the third evaporation chamber, and the second Ga evaporation source and the second In evaporation source are both communicated with the fourth evaporation chamber; An H2S air intake system communicates with the fourth evaporation chamber; The temperature control system is arranged in the preheating chamber, the evaporation chamber and the cooling chamber, and is used to control the temperature of the preheating chamber, the evaporation chamber and the cooling chamber.

2. The device for preparing the high-efficiency ultra-thin CIGS solar cell absorption layer according to claim 1, characterized in that: An inlet door is arranged at the entrance of the preheating chamber, an outlet door is arranged at the outlet of the cooling chamber, and isolation doors are arranged between the preheating chamber, the first evaporation chamber, the second evaporation chamber, the third evaporation chamber, the fourth evaporation chamber and the cooling chamber.

3. The device for preparing the high-efficiency ultra-thin CIGS solar cell absorption layer according to claim 2, characterized in that: The chamber entrance door and the isolation door are both provided with position sensors.

4. The device for preparing the high-efficiency ultra-thin CIGS solar cell absorption layer according to claim 1, characterized in that: The communicating pipeline is provided with a control valve.

5. The device for preparing the high-efficiency ultra-thin CIGS solar cell absorption layer according to claim 1, characterized in that: The communicating pipe is provided with a pipe heating device.

6. A method for preparing an efficient ultra-thin CIGS solar cell absorption layer, characterized in that: Utilizing the device according to any one of claims 1 to 5, comprising the following steps: (1) Turn on the vacuum system and evacuate the preheating chamber and evaporation chamber to a vacuum degree of 3.0×10 -6 mbar; turn on the heating resistor wire and the temperature control system to control the temperature in the preheating chamber and the evaporation chamber at 340-360°C, turn on the evaporation source heating wire to make all evaporation sources reach the predetermined evaporation temperature, turn on the alkali metal evaporation source and the Se evaporation source to fill the process chamber with Se and alkali metal vapor, of which the alkali metal vapor accounts for 0.08-0.1%; (2) sending the substrate into a preheating chamber for preheating; (3) transferring the preheated substrate to the first evaporation chamber, and co-evaporating and depositing Ga on the back electrode at a Ga deposition rate of 30 to 50 nm / min for 3 to 5 min; (4) Transferring to the second evaporation chamber, co-evaporating and depositing In, the In deposition rate is 30-50 nm / min, and the time is 3-5 min; (5) transferring to the third evaporation chamber to co-evaporate and deposit Cu at a Cu deposition rate of 50 to 70 nm / min for 4 to 6 min; (6) transferring to the fourth evaporation chamber, co-evaporating and compensating Ga and In in a H2S atmosphere, with a compensating deposition rate of 30-50 nm / min for 1-2 min, and an atomic fraction ratio of Cu:In:Ga:Se of (28-35):(8-15):(4-7):(40-55); (7) The product is transferred to a cooling chamber for cooling, thereby completing the preparation of the CIGS solar cell absorption layer.

7. The method for preparing a high-efficiency ultra-thin CIGS solar cell absorption layer according to claim 6, characterized in that: The alkali metal evaporation source is a Na evaporation source or a Na2S evaporation source.

8. The method for preparing a high-efficiency ultra-thin CIGS solar cell absorption layer according to claim 6, characterized in that: After the Cu is evaporated and deposited in step (5), it is necessary to detect whether the deposited film is rich in Cu. If the film is rich in Cu, it is sent to the fourth chamber.

9. A method for preparing a high-efficiency ultra-thin CIGS solar cell, characterized in that: The absorption layer of the high-efficiency ultra-thin CIGS solar cell is prepared by the method described in any one of claims 6 to 8.

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