Band Gap Adjustable Antimony Selenosulfide Indoor Photovoltaics with 20% Efficiency

Antimony selenosulfide Sb 2 (S x Se 1− x ) 3 is featured as a stable, environment‐friendly, and low‐cost light‐harvesting material with a tunable bandgap in the range of 1.1–1.8 eV, satisfying the requirement of indoor photovoltaics (IPVs). Up to now, the certified efficiency of Sb 2 (S x Se 1− x ) 3 solar cell with 1.45 eV bandgap has broken 10% under standard illumination (AM1.5G). However, this bandgap is not suitable for IPVs in terms of spectral matching. Herein, for the first time, the effect of optical bandgap of Sb 2 (S x Se 1− x ) 3 on photovoltaic performance of the devices under AM1.5G and indoor light conditions is studied systematically. It is discovered that although an appropriate Se/S atomic ratio is beneficial for improving the crystallinity of Sb 2 (S x Se 1− x ) 3 film and passivating the trap states, the band gap remains a key factor in determining the suitability of this material for IPVs. As a result, solar cells based on Sb 2 S 3 with a large bandgap of 1.74 eV achieve an optimal efficiency of 20.34% under 1000 lux indoor illumination. Moreover, a high IPV efficiency of over 16% can still be maintained within a wide bandgap range from 1.5 to 1.7 eV, demonstrating the great potential of Sb‐based chalcogenide as a light‐harvesting material for IPVs.