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Antimony sulfide (Sb₂S₃) is a highly promising environmentally friendly semiconductor for the development of stable thin-film solar cells, owing to its high absorption coefficient, suitable bandgap ( ~ 1.7 eV), and the abundance of its constituent elements. Conventionally, CdS is employed as a buffer layer in CdS/Sb₂S₃/spiro/Au-structured solar cells. However, due to its intrinsic defects, various strategies have been implemented to enhance device performance and improve the power conversion efficiency (PCE) of Sb₂S₃ solar cells. In this study, we first fabricated a SnO₂ electron transport layer (ETL) and subsequently optimized the water bath temperature to achieve a smoother CdS layer. Furthermore, a La³⁺ ion doping process was introduced to further decrease the resistance of the CdS layer. The incorporation of an appropriate concentration of La³⁺ into the CdS layer effectively redeced its resistivity. By integrating these enhancements, we developed a La-doped CdS/SnO₂ double ETL structure. The grain size of Sb₂S₃ deposited on the 1% La-doped CdS/SnO₂ double ETL was significantly increased, leading to a substantial reduction in grain boundary density. This improvement minimized non-radiative recombination at both the grain boundaries and the CdS/Sb₂S₃ heterointerface while simultaneously enhancing charge-carrier transport across the heterojunction. Consequently, the optimized solar cell achieved an open-circuit voltage (VOC) of 749 mV and a short-circuit current density (Jsc) of 17.01 mA/cm2, resulting in a power conversion efficiency (PCE) of 7.66%. This work presents an effective doping strategy to enhance the performance of the CdS buffer layer, offering valuable insights for the advancement of Sb₂S₃-based thin-film solar cells.
Zhang et al. (Tue,) studied this question.