Influence of Sulfur Source on Growth of In-Air Sprayed Ultrathin Film Sb₂S₃ for Enhanced Solar Cell Performance

Addressing the critical need for scalable and efficient production of high-quality antimony sulfide (Sb₂S₃) ultrathin films for next-generation solar cell technologies, this study introduces a novel, industrially scalable approach utilizing ultrasonic spray pyrolysis with antimony trichloride (SbCl₃) and thiourea precursors. This contrasts sharply with record Sb₂S₃ solar cells, often exceeding 200 nm and fabricated by using time-consuming chemical bath deposition, which presents challenges for tandem device integration. This work successfully fabricated high-quality 70 nm Sb₂S₃ ultrathin films. Extensive characterization revealed that excess thiourea addition in the Sb:S 1:6 ratio significantly reduced the growth rate, crucial for achieving ultrathin films, while simultaneously improving stoichiometry, morphology, and carrier transport, resulting in more homogeneous films. Devices fabricated with these optimized films demonstrated a substantial fill factor improvement, reaching 62%, comparable to the best reported values for Sb₂S₃ solar cells. This translated to a maximum power conversion efficiency of 5.3%. The films fabricated with the optimized thiourea addition in the Sb:S 1:6 ratio exhibited near-optimal stoichiometry, leading to a wider depletion width and improved device performance. This study proves the significance of precise precursor molar ratio control for high-quality ultrathin films, setting the stage for scalable Sb₂S₃ solar cells and advancing solution-processed photovoltaic technologies.