Preparation method of copper-indium-gallium-selenium thin film and preparation method of photoelectric device

Abstract

The application provides a preparation method of a copper-indium-gallium-selenium thin film, comprising the following steps: S10, heating a substrate to a first temperature, and co-evaporating indium, gallium and selenium on the substrate; S20, increasing the temperature of the substrate to a second temperature, and co-evaporating copper and selenium on the substrate; S30, keeping the temperature of the substrate as the second temperature, and co-evaporating indium, gallium and selenium on the substrate to obtain the copper-indium-gallium-selenium thin film; wherein the vapor pressure of selenium in step S10 is 4-8 times of the vapor pressure of selenium in step S30, the vapor pressure of selenium in step S20 is 2-8 times of the vapor pressure of selenium in step S10; and the vapor pressure of indium and gallium in step S10 is 4-8 times of the vapor pressure of indium and gallium in step S30. In the process of preparing the copper-indium-gallium-selenium thin film by the three-step co-evaporation method, by adjusting the vapor pressure of selenium in each co-evaporation step, the thin film growth environment of the reaction chamber of the co-evaporation equipment can be more stable, so that the growth of the high-quality thin film is facilitated, and the waste of the selenium source can be avoided, so that the depletion time of the solid selenium source can be more accurately controlled.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device technology, specifically relating to a method for preparing a copper indium gallium selenide thin film, and also to a method for preparing an optoelectronic device. Background Technology

[0002] Copper indium gallium selenide (CIGS) thin-film semiconductors possess continuously tunable bandwidths between 1.0 eV and 1.7 eV and high absorption coefficients (10⁻⁶). 5 CIGS thin films, with their excellent electrical and optical properties such as high density (cm²) and good low-light performance, have significant application value in optoelectronics and photovoltaic solar energy. Currently, the main methods for preparing CIGS thin films include sputtering followed by selenization, thermal spraying, electrodeposition, and a three-step co-evaporation method. Among these, the three-step co-evaporation method offers unique advantages such as precise control over film thickness and accurate controllability of film composition in the thickness direction, making it irreplaceable in the preparation of CIGS semiconductor materials.

[0003] The use of selenium source in the co-evaporation method for preparing CIGS thin films has always been a technical challenge due to the inherent physical and chemical properties of selenium. During selenization, H₂Se gas is often chosen as the selenium source due to its high reactivity and good diffusivity, as it readily forms stable compounds with the pre-formed layer. However, the toxicity and explosiveness of H₂Se gas limit its large-scale application. Currently, an alternative is to use solid selenium, which has lower toxicity and a higher safety factor. However, the selenium vapor obtained from solid selenium at high temperatures consists of Se molecules of different sizes. n Se molecules are composed of (2≤n≤8) atomic groups, and the chemical reactivity of these different atomic groups varies. Among them, the large Se molecule... n (n≥5) has low chemical activity, which is not conducive to growing CIGS films with good crystallinity and density under low temperature conditions.

[0004] To address the above problems, the current solution is to use large Se molecules. n Cleavage into small molecule Se n To enhance its chemical activity, for example, a high-temperature pyrolysis furnace is used. First, solid selenium is evaporated into Se vapor of different molecular sizes, and then further pyrolyzed at high temperature to convert the large Se molecules into larger Se vapor. n Cleavage into small molecule Se nAlthough the problem of generating a highly active and stable selenium beam has been solved, controlling the selenium vapor beam flow rate remains an issue in the three-step co-evaporation process for preparing CIGS thin films. In existing three-step co-evaporation processes for CIGS thin films, the selenium vapor beam flow rate is typically maintained in excess and at a constant flow rate throughout the entire process, as disclosed in Chinese patent application (publication number: CN103710668A) for the preparation of copper indium gallium selenide (CIGS) thin films. This approach leads to unstable pressure in the reaction chamber of the co-evaporation equipment and waste of expensive selenium sources. For example, in the second step of co-evaporating copper and selenium, the growth rate of copper is relatively high, requiring a large amount of selenium. Maintaining the same beam flow rate as in the first step can easily cause significant fluctuations in the pressure environment required by the co-evaporation growth chamber, which is detrimental to the growth of high-quality thin films. In the third step of co-evaporating indium, gallium, and selenium, the growth of indium and gallium is much smaller than in the first step, requiring less selenium. Maintaining the same beam flow rate as in the first step would result in waste of selenium sources. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a method for preparing copper indium gallium selenide (CIGS) thin films to solve the problems of unstable pressure in the reaction chamber and waste of selenium source caused by improper selenium vapor supply in the existing CIGS thin film preparation process.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a copper indium gallium selenide (CIGS) thin film includes the following steps:

[0008] S10. Heat the substrate to a first temperature and co-evaporate indium, gallium and selenium on the substrate;

[0009] S20. Increase the temperature of the substrate to a second temperature, and co-evaporate copper and selenium on the substrate;

[0010] S30. Maintaining the temperature of the substrate at a second temperature, co-evaporating indium, gallium, and selenium on the substrate to obtain a copper indium gallium selenide thin film.

[0011] In step S10, the vapor pressure of selenium is 4 to 8 times that of selenium in step S30; in step S20, the vapor pressure of selenium is 2 to 8 times that of selenium in step S10; and in step S10, the vapor pressures of indium and gallium are 4 to 8 times that of indium and gallium in step S30.

[0012] Specifically, the selenium vapor in steps S10 to S30 is small molecule selenium vapor provided after evaporating and cracking solid selenium using a high-temperature cracking furnace.

[0013] In a preferred embodiment, the high-temperature pyrolysis furnace includes a low-temperature evaporation zone and a high-temperature pyrolysis zone, and the evaporation and pyrolysis of solid selenium using the high-temperature pyrolysis furnace includes:

[0014] Solid selenium is placed in the low-temperature evaporation zone, which is then heated to a temperature T1 and held for a time t1; the temperature T1 is 90℃~110℃, and the time t1 is 1.5h~2.5h.

[0015] The low-temperature evaporation zone is further heated to temperature T2, and the high-temperature pyrolysis zone is heated to temperature T3 and held for time t2; the temperature T2 is 290℃~310℃, the temperature T3 is 440℃~460℃, and the time t2 is 1.5h~2.5h.

[0016] The low-temperature evaporation zone is further heated to temperature T4, and the high-temperature pyrolysis zone is further heated to temperature T5 and held for time t3; the temperature T4 is 370℃~390℃, the temperature T5 is 480℃~520℃, and the time t3 is 3.5h~4.5h.

[0017] The high-temperature pyrolysis zone is further heated to temperature T6 to pyrolyze the selenium vapor in the high-temperature pyrolysis zone; the temperature T6 is 600℃~750℃.

[0018] In a preferred embodiment, the high-temperature pyrolysis furnace evaporates and pyrolyzes solid selenium into small-molecule selenium vapor, which is then supplied to the reaction chamber of the co-evaporation equipment. When the vapor pressure of selenium in the reaction chamber of the co-evaporation equipment reaches 2 × 10⁻⁶... -3 When the temperature is above Pa, the process of step S10 begins; when the process of step S30 is completed, the supply of selenium vapor to the reaction chamber of the co-evaporation equipment is stopped when the temperature of the substrate drops below 200°C.

[0019] In a preferred embodiment, during steps S10 to S30, the pressure of the selenium vapor is adjusted to maintain the pressure within the reaction chamber of the co-evaporation equipment at 2 × 10⁻⁶. -3 Pa ~ 5 × 10 -2 Within the range of Pa.

[0020] In a preferred embodiment, the first temperature is 340℃~390℃, and the second temperature is 480℃~600℃.

[0021] In a preferred embodiment, the preparation method further includes: performing vacuum heat treatment on the copper indium gallium selenide thin film under a selenium atmosphere.

[0022] In a preferred embodiment, the vacuum heat treatment temperature is 350℃~550℃ and the time is 30min~90min.

[0023] Another aspect of the present invention is to provide a method for fabricating an optoelectronic device, wherein a copper indium gallium selenide (CIGS) light-absorbing layer is formed using the method described above for fabricating a CIGS thin film.

[0024] In a preferred embodiment, the optoelectronic device is a thin-film solar cell, and the method for fabricating the thin-film solar cell includes:

[0025] S1. Provide a support substrate, and form a bottom electrode layer on the support substrate;

[0026] S2. A copper indium gallium selenide light-absorbing layer is formed on the bottom electrode layer using the aforementioned method for preparing copper indium gallium selenide thin films.

[0027] S3. A cadmium sulfide buffer layer is formed on the copper indium gallium selenide light-absorbing layer.

[0028] S4. A window layer is formed on the cadmium sulfide buffer layer;

[0029] S5. A top electrode layer is formed on the window layer to obtain the thin-film solar cell.

[0030] The method for preparing copper indium gallium selenide (CIGS) thin films provided in this invention, using a three-step co-evaporation process, controls the vapor pressure (i.e., relative beam flow rate) of selenium in the first step to be 4 to 8 times that in the third step, the vapor pressure of selenium in the second step to be 4 to 8 times that in the first step, and the vapor pressures of indium and gallium in the first step to be 4 to 8 times that in the third step. Compared with the prior art, this method has the following advantages:

[0031] (1) For the method of using a high-temperature pyrolysis furnace to provide selenium vapor, the vapor pressure in the pyrolysis furnace is initially high, especially for large molecular Se. n It is cleaved into small molecule Se. n Since the vapor pressure is higher thereafter, in the technical solution of the present invention, when co-evaporating indium, gallium and selenium in the first step, the growth rate of indium and gallium is increased, and the vapor pressure of selenium vapor is also increased. This avoids excessive selenium vapor being trapped in the high-temperature pyrolysis zone of the pyrolysis furnace, which would result in excessively high vapor pressure and improve the stability of the thin film growth system.

[0032] (2) When copper and selenium are co-evaporated in the second step, the growth rate of copper is relatively large and the required amount of selenium is also relatively large. Therefore, the vapor pressure of selenium vapor is further increased in the second step, which not only meets the selenium requirement for material preparation, but also avoids the rapid decrease of selenium in the reaction chamber and the resulting pressure loss, which is conducive to the growth of high-quality thin films.

[0033] (3) When co-evaporating indium, gallium and selenium in the third step, the growth of indium and gallium is reduced, and the required amount of selenium is also less. Therefore, the vapor pressure of selenium vapor is reduced to avoid waste of selenium source. In addition, since the required amount of selenium is also less in this step, the evaporation of selenium source in the low-temperature evaporation zone of the high-temperature cracking furnace can be stopped in advance, and the selenium vapor that has been cracked in the high-temperature cracking zone can be used to maintain the required amount of selenium in this step, avoiding excessive evaporation of selenium source. Thus, the depletion time of solid selenium source can be controlled more accurately. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the thin-film solar cell prepared in the embodiments of the present invention;

[0035] Figure 2 This is a flowchart of the method for preparing copper indium gallium selenide thin films in the embodiments of the present invention;

[0036] Figure 3 This is a current-voltage curve of the thin-film solar cell prepared in the embodiments of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0038] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0039] This invention first provides a method for preparing a copper indium gallium selenide (CIGS) thin film, the method comprising the following steps:

[0040] Step S10: Heat the substrate to a first temperature, and co-evaporate indium, gallium, and selenium on the substrate. The first temperature is relatively low, preferably between 340°C and 390°C, for example, 340°C, 350°C, 360°C, 370°C, 380°C, or 390°C.

[0041] Step S20: Increase the temperature of the substrate to a second temperature, and co-evaporate copper and selenium on the substrate. The second temperature is relatively high, preferably between 480°C and 600°C, for example, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, or 600°C.

[0042] Step S30: Maintain the temperature of the substrate at a second temperature, and co-evaporate indium, gallium, and selenium on the substrate to obtain a copper indium gallium selenide thin film.

[0043] The selenium vapor in steps S10 to S30 is small molecule selenium vapor provided by evaporating and cracking solid selenium using a high-temperature cracking furnace.

[0044] In the embodiment of the present invention: the vapor pressure of selenium in step S10 is 4 to 8 times that of selenium in step S30, for example, 4, 5, 6, 7, or 8 times, preferably 4 to 5 times; the vapor pressure of selenium in step S20 is 2 to 8 times that of selenium in step S10, for example, 2, 3, 4, 5, 6, 7, or 8 times, preferably 2 to 4 times; the vapor pressure of indium and gallium in step S10 is 4 to 8 times that of indium and gallium in step S30, for example, 4, 5, 6, 7, or 8 times, preferably 6 to 8 times. It should be noted that the above-described vapor pressure multiples are consistent with the multiples of the flow rate of the corresponding element vapors entering the reaction chamber.

[0045] The method for preparing copper indium gallium selenide (CIGS) thin films according to embodiments of the present invention, in the process of preparing CIGS thin films using a three-step co-evaporation method, can make the film growth environment in the reaction chamber of the co-evaporation equipment more stable by adjusting the vapor pressure of selenium in each co-evaporation step, which is conducive to the growth of high-quality films. It can also avoid the waste of selenium source and thus more accurately control the depletion time of solid selenium source.

[0046] In the specific scheme, the high-temperature pyrolysis furnace includes a low-temperature evaporation zone and a high-temperature pyrolysis zone, and the evaporation and pyrolysis of solid selenium using the high-temperature pyrolysis furnace includes the following steps:

[0047] S100. Solid selenium is placed in the low-temperature evaporation zone, and the low-temperature evaporation zone is heated to a temperature T1 and held for a time t1. This step is mainly to remove moisture from the equipment. The temperature T1 can be set to 90℃~110℃, preferably 100℃. The time t1 can be set to 1.5h~2.5h, preferably 2h.

[0048] S200: The low-temperature evaporation zone is further heated to temperature T2, and the high-temperature pyrolysis zone is heated to temperature T3 and held for time t2. This step mainly aims to melt the solid selenium in the low-temperature evaporation zone and preheat the high-temperature pyrolysis zone. Temperature T2 can be set to 290℃~310℃, preferably 300℃. Temperature T3 can be set to 440℃~460℃, preferably 450℃. Time t2 can be set to 1.5h~2.5h, preferably 2h.

[0049] In a further preferred embodiment, during the heating process in step S200, the temperature of the low-temperature evaporation zone and the high-temperature pyrolysis zone is maintained at the current temperature for several minutes after each 100°C increase before the heating continues.

[0050] S300: The low-temperature evaporation zone is further heated to temperature T4, and the high-temperature pyrolysis zone is further heated to temperature T5 and held for time t3. This step mainly involves melting and evaporating the solid selenium in the low-temperature evaporation zone, and further heating the high-temperature pyrolysis zone towards the pyrolysis temperature. Temperature T4 can be set to 370℃~390℃, preferably 380℃. Temperature T5 can be set to 480℃~520℃, preferably 500℃. Time t3 can be set to 3.5h~4.5h, preferably 4h.

[0051] S400, The high-temperature pyrolysis zone is further heated to temperature T6 to pyrolyze the selenium vapor in the high-temperature pyrolysis zone. This step mainly involves further heating the temperature of the high-temperature pyrolysis zone to the pyrolysis temperature to pyrolyze the selenium vapor evaporated in the low-temperature evaporation zone, primarily to pyrolyze the large molecular Se. n Cleavage into small molecule Se n This enhances the chemical activity of selenium vapor. The temperature T6 can be set to 600℃~750℃, preferably 700℃.

[0052] In the specific scheme, the high-temperature pyrolysis furnace evaporates and pyrolyzes solid selenium into small-molecule selenium vapor, which is then supplied to the reaction chamber of the co-evaporation equipment: when the vapor pressure of selenium in the reaction chamber of the co-evaporation equipment reaches 2×10 -3 When the temperature is above Pa, the process of step S10 begins; when the process of step S30 is completed, the supply of selenium vapor to the reaction chamber of the co-evaporation equipment is stopped when the temperature of the substrate drops below 200°C.

[0053] In the specific implementation, during steps S10 to S30, the pressure of the selenium vapor is adjusted to maintain the pressure within the reaction chamber of the co-evaporation equipment at 2 × 10⁻⁶. -3 Pa ~ 5 × 10 -2 Maintaining the pressure within the Pa range is beneficial for growing high-quality copper indium gallium selenide (CIGS) thin films. Keeping the pressure within the reaction chamber of the co-evaporation equipment within a stable range is advantageous for obtaining high-quality CIGS thin films.

[0054] In a further preferred embodiment, after the process in step S30 is completed, the following treatment is performed: the copper indium gallium selenide (CIGS) thin film is subjected to vacuum heat treatment in a selenium atmosphere. The temperature of the vacuum heat treatment can be set to 350℃~550℃, for example, 350℃, 400℃, 450℃, 500℃, or 550℃; the annealing time can be set to 30min~90min, for example, 30min, 40min, 50min, 60min, 70min, 80min, or 90min, and the specific annealing time parameters need to be controlled according to the thickness of the thin film.

[0055] This invention also provides a method for fabricating an optoelectronic device, wherein a copper indium gallium selenide (CIGS) light-absorbing layer is formed using the method described above for fabricating a CIGS thin film.

[0056] Example 1

[0057] This embodiment provides a method for fabricating a thin-film solar cell, wherein the light-absorbing layer in the thin-film solar cell is formed using the method for fabricating a copper indium gallium selenide (CIGS) thin film provided in this embodiment of the invention. The structure of the thin-film solar cell is as follows: Figure 1 As shown, combined with Figure 1 The fabrication process of the thin-film solar cell includes the following steps:

[0058] S1. Provide a support substrate 1, and form a bottom electrode layer 2 on the support substrate 1.

[0059] Specifically, a cleaned soda-lime glass substrate is placed in a magnetron sputtering chamber, and a Cu-Mo alloy back electrode layer is sputtered and deposited using a Cu and Mo alloy target or a Cu and Mo dual target.

[0060] S2. A copper indium gallium selenide (CIGS) thin film is prepared on the bottom electrode layer 2 to form a CIGS light absorption layer 3.

[0061] Specifically, step S2 includes:

[0062] I. Preparation of selenium vapor:

[0063] (1) Add about 2.5 kg of Se particles (purity 99.99%) to the low-temperature evaporation zone of the high-temperature pyrolysis furnace;

[0064] (2) Heat the low-temperature evaporation zone to 100°C and maintain it for about 2 hours to remove water vapor;

[0065] (3) Heat the low-temperature evaporation zone and the high-temperature pyrolysis zone of the high-temperature pyrolysis furnace to 300°C and 450°C respectively. Stabilize the temperature of the low-temperature evaporation zone and the high-temperature pyrolysis zone for several minutes after each 100°C increase. Stop heating when the low-temperature evaporation zone reaches 300°C. Continue heating the high-temperature pyrolysis zone to 450°C. Then maintain this temperature for about 2 hours to melt the Se particles.

[0066] (4) The low-temperature evaporation zone and the high-temperature pyrolysis zone of the high-temperature pyrolysis furnace are heated to 380℃ and 500℃ respectively, and maintained for 4 hours. The Se particles melt and evaporate to form selenium vapor, which contains Se molecules of different sizes. n (2≤n≤8);

[0067] (5) Raise the temperature of the high-temperature pyrolysis zone of the high-temperature pyrolysis furnace to 650°C, and remove the large Se molecules in the selenium vapor. n Cleavage into small molecule Se n .

[0068] II. Preparation of copper indium gallium selenide thin films using a three-step co-evaporation method

[0069] First, the substrate from step S1 is placed onto the sample holder of the co-evaporation equipment (molecular beam epitaxy, MBE). Then, the reaction chamber of the co-evaporation equipment (molecular beam epitaxy, MBE) is evacuated to a vacuum level of 2 × 10⁻⁶. -5 Below Pa.

[0070] See Figure 2 The three-step co-distillation process includes the following steps:

[0071] S10. Heat the substrate to 390°C, and co-evaporate indium, gallium, and selenium onto the substrate. Specifically, selenium vapor is first introduced into the reaction chamber, and when the selenium pressure in the reaction chamber reaches 2 × 10⁻⁶... -3 At Pa, indium and gallium are introduced for co-evaporation.

[0072] like Figure 2 As shown, in this embodiment, the relative beam current of indium is 16, the relative beam current of gallium is 12, and the relative beam current of selenium is 24. The co-evaporation time in this step is 36 minutes.

[0073] S20. Increase the temperature of the substrate to 590°C and co-evaporate copper and selenium on the substrate.

[0074] like Figure 2 As shown, firstly, the selenium beam flux is increased and the substrate temperature is raised from 390°C to 590°C over a period of 5 minutes. After the substrate temperature reaches 590°C, copper is introduced to begin co-evaporation of copper and selenium. In this embodiment, the relative beam flux of copper is 20, and the relative beam flux of selenium is 48. The co-evaporation time in this step is 17 minutes.

[0075] S30. Maintaining the substrate temperature at 590°C, co-evaporate indium, gallium, and selenium on the substrate to obtain a copper indium gallium selenide thin film.

[0076] like Figure 2 As shown, the substrate temperature was maintained at 590°C and the selenium beam flow rate was reduced, while indium and gallium were co-evaporated. In this embodiment, the relative beam flow rate of indium was 2, the relative beam flow rate of gallium was 1.5, and the relative beam flow rate of selenium was 6. The co-evaporation time in this step was 17 minutes.

[0077] After the process in step S30 above is completed, the heating of the substrate is stopped and it is allowed to cool naturally. When the temperature of the substrate drops to 200°C, the supply of selenium vapor to the reaction chamber of the co-evaporation equipment is stopped.

[0078] In this embodiment, after obtaining the copper indium gallium selenide (CIGS) thin film as described above, the CIGS thin film is further subjected to vacuum heat treatment. Specifically, the substrate on which the CIGS thin film has been prepared is placed in a vacuum heat treatment device, selenium vapor is introduced, and vacuum heat treatment is performed under a selenium atmosphere. For example, the treatment temperature is 400°C and the heat treatment time is 50 minutes.

[0079] Based on the above process, a copper indium gallium selenide light-absorbing layer 3 is formed on the bottom electrode layer 2.

[0080] S3. A cadmium sulfide buffer layer 4 is formed on the copper indium gallium selenide light-absorbing layer 3.

[0081] Specifically, in this embodiment, 5.694 g of thiourea was dissolved in 150 mL of deionized water, 0.184 g of cadmium sulfate was dissolved in 60 mL of deionized water, and 45 mL of 30% ammonia solution was added. 425 mL of deionized water was poured into the reactor. The mixture of thiourea solution, cadmium sulfate, and ammonia solution was introduced into the reactor. The heat-treated sample was placed in the center of the reactor and placed in a 69°C constant-temperature water bath. The stirrer was turned on, and the CdS buffer layer material was uniformly grown using a chemical water bath method. After reacting for 10 min, the instrument was turned off, the sample was removed, quickly rinsed with deionized water, dried with N2, and annealed in a 160°C oven for 2 min, thereby preparing the cadmium sulfide buffer layer 4.

[0082] S4. A window layer 5 is formed on the cadmium sulfide buffer layer 4.

[0083] Specifically, the window layer 5 includes an intrinsic zinc oxide (IZO) layer 51 and an aluminum-doped zinc oxide (AZO) layer 52. When sputtering the intrinsic zinc oxide layer, the argon flow rate is 20 sccm, the oxygen flow rate is 2.0 sccm, and sputtering is performed 4 times at a sputtering power of 120 W. Subsequently, the power is adjusted to 220 W for 16 sputterings. When sputtering the aluminum-doped zinc oxide 52, the substrate temperature is heated to 90°C, the argon flow rate is 20 sccm, the hydrogen flow rate is 2.5 sccm, and sputtering is performed 12 times at a sputtering power of 750 W.

[0084] S5. A top electrode layer 6 is formed on the window layer 5 to obtain the thin-film solar cell.

[0085] In this embodiment, the electrical properties of the thin-film solar cells prepared in the above embodiments are tested. Figure 3 This is the current-voltage characteristic curve obtained from the test. According to... Figure 3 The voltage-current characteristic curves shown indicate that the open-circuit voltage (Voc) of the thin-film solar cell prepared in the above embodiments is 733mV, and the short-circuit current (Isc) is 33.6mA / cm. 2 With a fill factor (FF) of 78.01% and an efficiency (Eff) of 19.21%, it exhibits excellent electrical performance.

[0086] In summary, this invention, through the three-step co-evaporation method for preparing copper indium gallium selenide (CIGS) thin films, achieves a more stable film growth environment in the reaction chamber of the co-evaporation equipment by controlling the vapor pressure of selenium in each co-evaporation step. This is beneficial for the growth of high-quality thin films and also avoids the waste of selenium source, allowing for more precise control of the depletion time of the solid-state selenium source. Applying this method to the preparation of CIGS light-absorbing layers for thin-film solar cells can improve the crystallinity and density of the light-absorbing layer, resulting in thin-film solar cells with excellent electrical performance.

[0087] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a copper indium gallium selenide (CIGS) thin film, characterized in that, Includes the following steps: S10. Heat the substrate to a first temperature and co-evaporate indium, gallium and selenium on the substrate; S20. Increase the temperature of the substrate to a second temperature, and co-evaporate copper and selenium on the substrate; S30. Maintaining the temperature of the substrate at a second temperature, co-evaporating indium, gallium, and selenium on the substrate to obtain a copper indium gallium selenide thin film. In step S10, the vapor pressure of selenium is 4 to 8 times that of selenium in step S30; in step S20, the vapor pressure of selenium is 2 to 8 times that of selenium in step S10; and in step S10, the vapor pressures of indium and gallium are 4 to 8 times that of indium and gallium in step S30. The selenium vapor in steps S10 to S30 is small molecule selenium vapor provided by evaporating and cracking solid selenium using a high-temperature cracking furnace. The high-temperature pyrolysis furnace includes a low-temperature evaporation zone and a high-temperature pyrolysis zone, and the evaporation and pyrolysis of solid selenium using the high-temperature pyrolysis furnace includes: Solid selenium is placed in the low-temperature evaporation zone, which is then heated to a temperature T1 and held for a time t1; the temperature T1 is 90℃~110℃, and the time t1 is 1.5h~2.5h. The low-temperature evaporation zone is further heated to temperature T2, and the high-temperature pyrolysis zone is heated to temperature T3 and held for time t2; the temperature T2 is 290℃~310℃, the temperature T3 is 440℃~460℃, and the time t2 is 1.5h~2.5h. The low-temperature evaporation zone is further heated to temperature T4, and the high-temperature pyrolysis zone is further heated to temperature T5 and held for time t3; the temperature T4 is 370℃~390℃, the temperature T5 is 480℃~520℃, and the time t3 is 3.5h~4.5h. The high-temperature pyrolysis zone is further heated to temperature T6 to pyrolyze the selenium vapor in the high-temperature pyrolysis zone; the temperature T6 is 600℃~750℃.

2. The method for preparing copper indium gallium selenide thin films according to claim 1, characterized in that, The high-temperature pyrolysis furnace evaporates and pyrolyzes solid selenium into small-molecule selenium vapor, which is then supplied to the reaction chamber of the co-evaporation equipment. When the vapor pressure of selenium in the reaction chamber of the co-evaporation equipment reaches 2 × 10⁻⁶... -3 When the temperature is above Pa, the process of step S10 begins; when the process of step S30 is completed, the supply of selenium vapor to the reaction chamber of the co-evaporation equipment is stopped when the temperature of the substrate drops below 200°C.

3. The method for preparing copper indium gallium selenide thin films according to claim 1, characterized in that, During the processes of steps S10 to S30, the pressure of the selenium vapor is adjusted to maintain the pressure in the reaction chamber of the co-evaporation equipment at 2 × 10⁻⁶. -3 Pa ~ 5 × 10 -2 Within the range of Pa.

4. The method for preparing a copper indium gallium selenide thin film according to claim 1, characterized in that, The first temperature is 340℃~390℃, and the second temperature is 480℃~600℃.

5. The method for preparing a copper indium gallium selenide thin film according to any one of claims 1-4, characterized in that, The preparation method further includes: performing vacuum heat treatment on the copper indium gallium selenide thin film under a selenium atmosphere.

6. The method for preparing a copper indium gallium selenide thin film according to claim 5, characterized in that, The vacuum heat treatment is performed at a temperature of 350℃ to 550℃ for a time of 30 min to 90 min.

7. A method for fabricating an optoelectronic device, characterized in that, A copper indium gallium selenide (CIGS) light-absorbing layer is prepared using the method described in any one of claims 1-6.

8. The method for fabricating an optoelectronic device according to claim 7, characterized in that, The optoelectronic device is a thin-film solar cell, and the method for preparing the thin-film solar cell includes: S1. Provide a support substrate, and form a bottom electrode layer on the support substrate; S2. A copper indium gallium selenide (CIGS) light-absorbing layer is formed on the bottom electrode layer using the method for preparing a CIGS thin film as described in any one of claims 1-6. S3. A cadmium sulfide buffer layer is formed on the copper indium gallium selenide light-absorbing layer. S4. A window layer is formed on the cadmium sulfide buffer layer; S5. A top electrode layer is formed on the window layer to obtain the thin-film solar cell.

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