Annealing process optimization method of wide band gap CuGaSe2 solar cell absorption layer
Through magnetron sputtering method and precise annealing process optimization, the problems of grain disorder and secondary phase generation of CGSe absorption layer are solved, and efficient grain growth and photoelectric conversion efficiency are achieved.
Patent Information
- Application Number
- CN202510584436.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-07
- Publication Date
- 2025-07-08
AI Technical Summary
In the existing CGSe absorption layer preparation process, the grains are small and disordered, resulting in low carrier mobility, insufficient device filling factor, and lack of precise control of annealing temperature and time, resulting in secondary phase generation and reducing battery efficiency.
Prefabricated films were prepared by magnetron sputtering method, combined with precise annealing temperature and time control, and selenium-rich targets were used to avoid H2Se gas. By annealing in an argon environment, grain growth was optimized and secondary phase generation was suppressed.
A CGSe absorbing layer with micron-scale grains was obtained, with a flat surface and an photoelectric conversion efficiency increased to 0.69%, avoiding cost and safety risks and improving device performance.
Smart Images
Figure CN120282574A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technology for preparing photovoltaic materials, and particularly to a process method for improving the performance of the absorption layer of a wide-bandgap CuGaSe2 (CGSe) solar cell by optimizing the annealing time and temperature parameters. Background Art
[0002] With the transformation of the global energy structure towards renewable energy, the technology of solar cells has been continuously innovated. The efficiency of single-junction solar cells has approached the Shockley-Queisser theoretical limit (about 33.7%), and tandem cells have become the key direction to break through the efficiency bottleneck due to their ability to absorb the solar spectrum in a graded manner. Among them, the wide-bandgap (~1.7 eV) CGSe material is regarded as an ideal candidate material for the top cell of tandem cells due to its high light absorption coefficient, elemental abundance, and stability. However, the practical application of the CGSe absorption layer still faces the following technical bottlenecks:
[0003] In traditional preparation processes (such as the three-stage co-evaporation method), small-sized grains (<1 μm) and a high density of grain boundaries are easily formed in the CGSe absorption layer. Grain boundaries, as carrier recombination centers, significantly reduce the carrier mobility and lifetime. The unoptimized annealing process results in disordered stacking of grains, and the fill factor (FF) of the device is less than 40%.
[0004] In the prior art, the annealing temperature and time often adopt empirical values (such as 500 - 600 °C, 10 - 60 minutes), but there is a lack of precise control over the grain growth kinetics and phase transformation law. For example, the comparative example shows that when the annealing temperature exceeds 570 °C, the content of the Cu 2-x Se phase in the CGSe absorption layer increases to 5% (detected by XRD), resulting in a sudden drop in the device efficiency to 0.13%. Therefore, it is urgent to develop an efficient and controllable annealing process to solve the above problems. Summary of the Invention
[0005] Aiming at the above problems, the present invention discloses an optimization method for the annealing process of the absorption layer of a wide-bandgap CuGaSe2 solar cell. By precisely controlling the annealing temperature, time, and the amount of selenium powder added, the generation of secondary phases is inhibited, the directional growth of grains is promoted, and the quality of the CGSe absorption layer and the device performance are significantly improved. The specific solutions are as follows:
[0006] S1: Using the magnetron sputtering method, deposit a CuGaSe2 prefilm on the Mo back electrode with a selenium-rich target. The sputtering parameters are 1×10 -3 Pa, the working pressure is 0.5 Pa, the argon flow rate is 30 sccm, and the RF power is 50 W.
[0007] S2: Place the prefabricated film in an argon environment for annealing treatment. The heating rate is 10 °C, the annealing temperature is 550 °C, and the holding time is 30 minutes. Then cool down, and take out the sample after the temperature drops to room temperature.
[0008] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0009] Firstly, a selenium-rich target is used, avoiding the use of toxic H2Se gas, reducing costs and safety risks. Under the optimal conditions (holding at 550 °C for 30 minutes), the obtained grain size of the absorption layer reaches the micron level, without secondary phases, with a flat surface, and the photoelectric conversion efficiency is increased to 0.69%. Description of the Drawings
[0010] Figure 1 It is the morphology of the CGSe absorption layer obtained in Examples 1-4 of the present invention.
[0011] Figure 2 It is the Raman shift spectrum of the CGSe absorption layer obtained in Examples 1-4 of the present invention.
[0012] Figure 3 It is the XRD spectrum of the CGSe absorption layer obtained in Examples 1-4 of the present invention. Detailed Embodiments
[0013] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.
[0014] Example 1
[0015] Step S1: Under a radio frequency power supply, a prefabricated film of CGSe (atomic ratio Cu:Ga:Se = 0.9:1.0:2.0) with a thickness of 1 μm is prepared by magnetron sputtering. The sputtering parameters are 1×10 -3 Pa, the working pressure is 0.5 Pa, the argon flow rate is 30 sccm, and the radio frequency power is 50 W;
[0016] Step S2: Place the prefabricated film in a tube furnace, pump the pressure in the quartz tube to 0.1 Pa and then introduce argon to one atmosphere, repeat three times, heat to 550 °C at a rate of 10 °C / min, hold for 30 minutes, and naturally cool to room temperature to obtain a CGSe absorption layer.
[0017] Figure 1The "550 °C" figure corresponds to the morphology of the CGSe absorption layer obtained in Example 1 of the present invention. The root mean square deviation value (Rq) of the surface roughness of the CGSe absorption layer is 4.9 nm. The cross-sectional grains are large, uniform in size, without pores, and the stacked structure is dense.
[0018] Figure 2 The "550 °C" curve corresponds to the Raman shift spectrum of the CGSe absorption layer obtained in Example 1 of the present invention, which is consistent with the CGSe peak position.
[0019] Figure 3 The "550 °C" curve corresponds to the XRD pattern of the CGSe absorption layer obtained in Example 1 of the present invention. The CGSe absorption layer is a single chalcopyrite phase, and each peak position corresponds to the CGSe standard card (JCPDS No. 31-0456).
[0020] Example 2
[0021] Step S1: Under a radio frequency power supply, a prefabricated film of CGSe (atomic ratio of Cu:Ga:Se = 0.9:1.0:2.0) with a thickness of 1 μm is prepared by magnetron sputtering. The sputtering parameters are 1×10 -3 Pa, working pressure 0.5 Pa, argon flow rate 30 sccm, radio frequency power 50 W;
[0022] Step S2: Place the prefabricated film in a tube furnace. Pump the pressure in the quartz tube to 0.1 Pa and then introduce argon to one atmosphere, repeat three times. Heat it to 470 °C at a rate of 10 °C / min, hold for 30 minutes, and then cool it naturally to room temperature to obtain the CGSe absorption layer.
[0023] Figure 1 The "470 °C" figure corresponds to the morphology of the CGSe absorption layer obtained in Example 1 of the present invention. The root mean square deviation value (Rq) of the surface roughness of the CGSe absorption layer is 1.6 nm. Due to the relatively low annealing temperature, the growth conditions of the absorption layer are not satisfied. The surface grains are dense but small in size, there are many grain boundaries, and the absorption layer is a stacked nanocrystal.
[0024] Figure 2 The "470 °C" curve corresponds to the Raman shift spectrum of the CGSe absorption layer obtained in Example 1 of the present invention, which is consistent with the CGSe peak position.
[0025] Figure 3 The "470 °C" curve corresponds to the XRD pattern of the CGSe absorption layer obtained in Example 1 of the present invention. The CGSe absorption layer is a single chalcopyrite phase, and each peak position corresponds to the CGSe standard card ((JCPDS No. 31-0456).
[0026] Example 3
[0027] Step S1: Under a radio frequency power supply, a prefabricated film of CGSe (atomic ratio of Cu:Ga:Se = 0.9:1.0:2.0) with a thickness of 1 μm is prepared by magnetron sputtering. The sputtering parameters are 1×10 -3 Pa, the working pressure is 0.5 Pa, the argon flow rate is 30 sccm, and the radio frequency power is 50 W;
[0028] Step S2: Place the prefabricated film in a tube furnace, pump the pressure in the quartz tube down to 0.1 Pa, introduce argon to one atmosphere, repeat three times, heat it up to 510 °C at a rate of 10 °C / min, hold for 30 minutes, and naturally cool to room temperature to obtain a CGSe absorption layer.
[0029] Figure 1 The "510 °C" figure corresponds to the morphology of the CGSe absorption layer obtained in Example 1 of the present invention. The root mean square deviation value (Rq) of the surface roughness of the CGSe absorption layer is 5.7 nm, the grain size increases, and the number of grain boundaries decreases. The existence of grain boundaries will lead to lattice mismatch between adjacent grains, carrier recombination occurs when carriers transfer between grains, and the effective mobility of carriers decreases.
[0030] Figure 2 The "510 °C" curve corresponds to the Raman shift spectrum of the CGSe absorption layer obtained in Example 1 of the present invention, which is consistent with the peak position of CGSe.
[0031] Figure 3 The "510 °C" curve corresponds to the XRD pattern of the CGSe absorption layer obtained in Example 1 of the present invention. The CGSe absorption layer is a single chalcopyrite phase, and each peak position corresponds to the CGSe standard card ((JCPDS No. 31-0456).
[0032] Example 4
[0033] Step S1: Under a radio frequency power supply, a prefabricated film of CGSe (atomic ratio of Cu:Ga:Se = 0.9:1.0:2.0) with a thickness of 1 μm is prepared by magnetron sputtering. The sputtering parameters are 1×10 -3 Pa, the working pressure is 0.5 Pa, the argon flow rate is 30 sccm, and the radio frequency power is 50 W;
[0034] Step S2: Place the prefabricated film in a tube furnace, pump the pressure in the quartz tube down to 0.1 Pa, introduce argon to one atmosphere, repeat three times, heat it up to 590 °C at a rate of 10 °C / min, hold for 30 minutes, and naturally cool to room temperature to obtain a CGSe absorption layer.
[0035] Figure 1The "590 °C" figure corresponds to the morphology of the CGSe absorption layer obtained in Example 1 of the present invention. The root mean square deviation value (Rq) of the surface roughness of the CGSe absorption layer is 7.0 nm. Some grains in the absorption layer further grow, but there is a large difference in grain size. The surface of the film becomes porous, possibly due to the volatilization of elements caused by too high temperature.
[0036] Figure 2 The "590 °C" curve corresponds to the Raman shift spectrum of the CGSe absorption layer obtained in Example 1 of the present invention. An additional Raman peak is detected at 257 cm -1 According to the literature survey, this peak belongs to Cu 2-x Se. It shows that when the annealing temperature is too high, there is a secondary phase Cu 2-x Se in the CGSe absorption layer.
[0037] Figure 3 The "590 °C" curve corresponds to the XRD pattern of the CGSe absorption layer obtained in Example 1 of the present invention. A peak located at 2θ = 27° is detected in the CGSe absorption layer, corresponding to the (111) orientation of the Cu 2-x Se secondary phase and the formation of the Cu 2-x Se phase.
Claims
1. An annealing process optimization method for the absorption layer of a wide-bandgap CuGaSe2 solar cell, characterized in that, Including the following steps: (1) Adopt the magnetron sputtering method to deposit a CuGaSe2 prefabricated film on the Mo back electrode with a selenium-rich target. The sputtering parameters are 1×10 -3 Pa, the working pressure is 0.5 Pa, the argon gas flow rate is 30 sccm, and the RF power is 50 W; (2) Place the prefabricated film in an argon environment for annealing treatment, with a heating rate of 8-12 °C, an annealing temperature of 470 °C - 590 °C, and a holding time of 20-40 minutes.
2. The annealing process according to claim 1, wherein The annealing temperature is preferably 550 °C, and the holding time is preferably 30 minutes.
3. The annealing process according to claim 1, characterized in that, Under the optimized conditions, the grain size of the CGSe absorption layer after annealing is 1-3 μm, without Cu 2-x Se secondary phase, and the surface roughness (Rq) ≤ 7.0 nm.
4. The annealing process according to claim 1, wherein Under the preferred conditions, the band gap width of the CGSe absorption layer after annealing is 1.57-1.72 eV, and the absorption coefficient is ≥90% in the wavelength range of ≤750 nm.
5. The annealing process according to claim 1, a CuGaSe2 solar cell prepared under preferred conditions, characterized in that, Its photoelectric conversion efficiency is ≥0.4%, and the carrier lifetime is ≥20 μs.