Ultrathin SnO<sub>2</sub> Buffer Layer Aids in Interface and Band Engineering for Sb<sub>2</sub>(S,Se)<sub>3</sub> Solar Cells with over 8% Efficiency
Xiaoli Mao, Moran Bian, Changxue Wang, Ru Zhou, Lei Wan, Zibin Zhang, Jun Zhu, Wangchao Chen, Chengwu Shi, Baomin Xu
Abstract
The environmentally friendly antimony selenosulfide (Sb2(S,Se)3) semiconductor emerges as a promising light harvester for thin-film photovoltaics owing to its excellent material and optoelectronic properties. The alloyed Sb2(S,Se)3 is endowed with the complementary benefits of Sb2S3 and Sb2Se3, such as a tunable band gap within the range of 1.10–1.70 eV. In Sb2(S,Se)3 solar cells, the n-type semiconductor CdS is extensively used as an electron transport layer (ETL), which plays a role in extracting photogenerated electrons from absorbers and transporting them to conducting substrates. However, the unsatisfactory ETL/absorber interface contact often involves severe interface recombination. Herein, we report that an ultrathin SnO2 buffer layer of ∼10 nm applied on the high-roughness fluorine-doped tin oxide (FTO) substrate aids in effective interface and band engineering for superstrate CdS/Sb2(S,Se)3 solar cells. Careful characterizations confirm that the ultrathin SnO2 buffer layer plays a positive role in inhibiting the shunt current leakage at the ETL/absorber interface and manipulating the cascade energy band structure for more effective interface passivation and efficient electron extraction. Consequently, the resultant SnO2/CdS ETL-based Sb2(S,Se)3 solar cells exhibited a remarkable device efficiency of 8.67%, coupled with a considerable open-circuit voltage of 0.72 V. Our finding demonstrates a facile approach to engineer the interface contact and band offset to accelerate electron extraction, transport, and collection efficiencies.