8.2%-Efficiency hydrothermal Sb2S3 thin film solar cells by two-step RTP annealing strategy

Antimony sulfide (Sb₂S₃) solar cells fabricated via hydrothermal deposition have attracted widespread attention. The annealing crystallization process plays a crucial role in achieving optimal crystallinity in hydrothermal Sb₂S₃ thin films. Nevertheless, incomplete crystallization and the loss of sulfur at high-temperature contribute to defect recombination, constraining device performance. Herein, a two-step rapid thermal processing (RTP) annealing strategy is proposed to improve the crystal quality and efficiency of Sb₂S₃ solar cells. The annealing process in Ar protection with atmospheric pressure can suppress S loss caused by saturated vapor pressure. The two-step RTP annealing with the 330°C low-temperature and 370°C high-temperature process ensures high crystallinity and vertical orientations of Sb₂S₃ thin films, accompanied by a reduction in defect concentration from 1.01 × 10¹² to 5.97 × 10¹¹ cm⁻³. The Sb₂S₃ solar cell achieves an efficiency of 8.20% with an enhanced open circuit voltage (V_OC) of 784 mV. The build-in voltage (V_bi) of 1.17 V and irradiation-dependent ideal factor (n) of 1.48 demonstrate enhanced heterojunction quality and suppressed defect recombination in the devices. The presented two-step annealing strategy and physical mechanism study will open new prospects for high-performance Sb₂S₃ solar cells.