4-Phenylthiosemicarbazide Molecular Additive Engineering for Wide-Bandgap Sn Halide Perovskite Solar Cells with a Record Efficiency Over 12.2%

Abstract

The utilization of wide bandgap (WBG) tin halide perovskites (Sn-HPs) offers an environmentally friendly alternative for multi-junction Sn-HP photovoltaics. Nonetheless, rapid crystallization leads to suboptimal film morphology and substantial creation of defect states, which undermine device efficiency. This study introduces 4-Phenylthiosemicarbazide (4PTSC) as an additive to achieve a densely packed Sn-HP film with fewer imperfections. The strong chemical coordination between SnI2 and the functional groups S═C─N (Sn···S═C─N), -NH2, and phenyl conjugation enhances solution stability and supports the delay of perovskite crystallization through adduct formation. This process yields pinhole-free films with preferred grain growth. 4PTSC acts as a strong coordination complex and a reducing agent to passivate uncoordinated Sn2+ and halide ions and reduce the formation of SnI4, thereby reducing defect formation. The π-conjugated phenyl ring in the 4PTSC facilitates the preferred crystal growth orientation of perovskite grains. Furthermore, the hydrophobic nature of 4PTSC mitigates Sn2+ oxidation by repelling moisture, enhancing stability. The open circuit voltage significantly increased from 0.78 to 0.94 V, resulting in achieving the champion efficiency of 12.22% (certified 11.70%), surpassing all previously reported efficiencies for WBG Sn halide perovskite solar cells. Additionally, the unencapsulated 4PTSC-1.0 device maintained outstanding stability over 1200 h under ambient atmospheric conditions.