Surface Cleaning and Trap Passivation of Solution-Crystallized AgBiS2 Thin Films for Improved Solar Cell Performance

Abstract

Surface defects and interfacial recombination losses often limit the performance of silver bismuth sulfide (AgBiS2) solar cells. Herein, we present a simple ultraviolet–ozone (UVO3) and subsequent water treatment (UVO3_water) strategy for surface engineering of solution-crystallized AgBiS2 thin films for improved solar cell efficiency without modifying the bulk crystal structure. Our results reveal that the UVO3 treatment removes residual organic impurities, induces surface oxygen-containing species possibly associated with S–O bonding, and subsequent water treatment (UVO3_water) promotes the formation of a Bi–O-rich surface (relative amount of 27%) on the surface of AgBiS2. This surface modification improves charge collection at the AgBiS2/poly(3-hexylthiophene-2,5 diyl, P3HT) interface and suppresses trap-assisted recombination. As a result, the optimized UVO3_water-treated solar cell achieves a power conversion efficiency (PCE) of 6.3%, with an exceptional short-circuit current density (Jsc) exceeding 39 mA cm–2, significantly higher than the previously reported value of 29.15 mA cm–2, and simultaneous improvement of open-circuit voltage (Voc) and fill factor (FF). Additionally, unencapsulated AgBiS2 solar cells exhibit good operational stability under continuous 1 Sun illumination, with efficiency increasing to 6.8%.