Double interface modification promotes efficient Sb2Se3 solar cell by tailoring band alignment and light harvest

SnO 2 and CdS interlayers are demonstrated to effectively improve the conduction band alignment and light harvest of Sb 2 Se 3 solar cell by forming SnO 2 /TiO 2 /CdS ETL, which drives the efficiency of Sb 2 Se 3 device to 7.0%. The band alignment at the front interfaces is crucial for the performance of Sb 2 Se 3 solar cell with superstrate configuration. Herein, a SnO 2 /TiO 2 thin film, demonstrated beneficial for carrier transport in Sb 2 Se 3 device by the first-principle calculation and experiment, is proposed to reduce the parasitic absorption caused by CdS and optimize the band alignment of Sb 2 Se 3 solar cell. Thanks to the desirable transmittance of SnO 2 /TiO 2 layer, the Sb 2 Se 3 solar cell with SnO 2 /TiO 2 /(CdS-38 nm) electron transport layer performances better than (CdS-70 nm)/Sb 2 Se 3 solar cell. The optimized band alignment, the reduced interface defects and the decreased current leakage of Sb 2 Se 3 solar cell enable the short-circuit current density, fill factor, open-circuit voltage and efficiency of the Sb 2 Se 3 solar cell increase by 26.7%, 112%, 33.1% and 250% respectively when comparing with TiO 2 /Sb 2 Se 3 solar cell without modification. Finally, an easily prepared SnO 2 /TiO 2 /CdS ETL is successfully applied on Sb 2 Se 3 solar cell by the first time and contributes to the best efficiency of 7.0% in this work, which is remarkable for Sb 2 Se 3 solar cells free of hole transporting materials and toxic CdCl 2 treatment. This work is expected to provide a valuable reference for future ETL design and band alignment for Sb 2 Se 3 solar cell and other optoelectronic devices.