Defect Engineering in Earth-Abundant Cu2ZnSn(S,Se)4 Photovoltaic Materials via Ga3+-Doping for over 12% Efficient Solar Cells |
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| Authors: | Yachao Du Shanshan Wang Qingwen Tian Yuechao Zhao Xiaohuan Chang Haiqin Xiao Yueqing Deng Shiyou Chen Sixin Wu Shengzhong |
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| Affiliation: | 1. Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an, 710119 China
Key Lab for Special Functional Materials of Ministry of Education, Henan University, Kaifeng, 475004 China;2. Key Laboratory of Polar Materials and Devices (Ministry of Education) and Department of Electronics, East China Normal University, Shanghai, 200241 China;3. Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an, 710119 China;4. Key Lab for Special Functional Materials of Ministry of Education, Henan University, Kaifeng, 475004 China |
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| Abstract: | The efficiency of earth-abundant Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is considerably lower than the Shockley–Queisser limit. One of the main reasons for this is the presence of deleterious cation disordering caused by SnZn antisite and 2CuZn+SnZn defect clusters, resulting in a short minority carrier lifetime and significant band tailing, leading to a large open-circuit voltage deficit, and hence, low efficiency. In this study, Ga-doping is used to increase the CZTSSe solar cell efficiency to as high as 12.3%, one of the highest for this type of cells. First-principles calculations show that the preference of Ga3+ occupying Zn and Sn sites has a benign effect on suppressing the formation of the SnZn deep donor defects by upwardly shifting the Fermi level, which is further confirmed by deep-level transient spectroscopy characterization. Besides, the Ga dopants can also form defect-dopant clusters, such as GaZn+CuZn and GaZn+GaSn, which also have positive effects on suppressing the band-tailing states. The defect engineering via Ga3+-doping may suppress the band-tailing defect with a decreased Urbach energy, elevate the minority carrier lifetime, and in the end, enhance the VOC from 473 to 515 mV. These results provide a new route to further increase CZTSSe-based solar cell efficiency by defect engineering. |
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| Keywords: | cation doping Cu
2ZnSn(S Se)
4 defect engineering kesterite thin-film solar cells thiol/amine |
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