Efficient Solar Cells Employing Light‐Harvesting Sb0.67Bi0.33SI

Sb1−xBixSI, an isostructural material with the well‐known quasi‐1D SbSI, possesses good semiconductive and ferroelectric properties but is not applied in solar cells. Herein, solar cells based on alloyed Sb0.67Bi0.33SI (ASBSI) as a light harvester are fabricated. ASBSI is prepared through the reaction of bismuth triiodide in N,N‐dimethylformamide solution with an antimony trisulfide film deposited on a mesoporous (mp)‐TiO2 electrode via chemical bath deposition at 250 °C under an argon or nitrogen atmosphere; the alloy exhibits a promising bandgap (1.62 eV). The best performing cell fabricated with poly[2,6‐(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] as the hole‐transporting layer shows 4.07% in a power conversion efficiency (PCE) under the standard illumination conditions of 100 mW cm−2. The unencapsulated cells exhibit good comprehensive stability with retention of 92% of zjr initial PCE under ambient conditions of 60% relative humidity over 360 h, 93% after 1 sun illumination for 1254 min, and 92% after storage at 85 °C in air for 360 h. Solar cells employing light‐harvesting alloyed Sb0.67Bi0.33SI (ASBSI) are demonstrated, which exhibit a power conversion efficiency of 4.07%. After incorporating Bi into Sb2S3, the bandgap decreases from 1.73 eV (Sb2S3) to 1.62 eV (ASBSI). This work paves the way for the application of alloy metal chalcohalogens in solar cells and provides intermediates for synthesizing new perovskite materials.