Synergistic Effect through the Introduction of Inorganic Zinc Halides at the Interface of TiO and SbS for High-Performance SbS Planar Thin-Film Solar Cells.

The competition between charge recombination and extraction principally affects the fill factor (FF) and power conversion efficiency (PCE) of planar thin-film solar cells. In SbS thin-film solar cells, the electrocharge recombination and extraction n transport layer (ETL) plays a significant role in electron extraction and determination of SbS film absorber quality. Herein, a TiO ETL is strategically modified using an inorganic salt zinc halide (i.e., ZnCl, ZnBr, ZnI), which simultaneously improves the electronic properties of TiO and promotes the growth of SbS films with larger grain size and higher crystallinity. The experimental results and theoretical calculations further reveal that the zinc halide can interact with TiO and simultaneously bond strongly with the upper SbS film, which creates a unique pathway for electron transfer, passivates the trap states, and alleviates the recombination losses effectively. As a result, an average PCE of 6.87 ± 0.11% and the highest PCE of 7.08% have been attained with an improved FF from 51.22 to 61.61% after ZnCl introduction. Additionally, introduction of ZnCl helps the unencapsulated devices to maintain 93% of their original performance after 2400 h of storage in a nitrogen-filled glovebox. This work develops an effective route for the optimization of ETLs and defect healing using simple and low-cost inorganic salts.