Direct Hydrothermal Deposition of Antimony Triselenide Films for Efficient Planar Heterojunction Solar Cells

Antimony selenide (Sb₂Se₃) has attracted increasing attention in photovoltaic applications due to its unique quasi-one-dimensional crystal structure, suitable optical band gap with a high extinction coefficient, and excellent stability. As a promising light-harvesting material, the available synthetic methods for the fabrication of a high-quality film have been quite limited and seriously impeded both the fundamental study and the efficiency improvement. Here, we developed a facile and low-cost hydrothermal method for in situ deposition of Sb₂Se₃ films for solar cell applications. In this process, we apply KSbC₄H₄O₇ and Na₂SeSO₃ as the antimony and selenium sources, respectively, in which thiourea (TU) serves as an additive to suppress the formation of Sb₂O₃ impurities. As a result, improved phase purity and enhanced crystallinity of the Sb₂Se₃ film are thus obtained, along with decreased trap states. Finally, the planar heterojunction Sb₂Se₃ solar cell delivered a power conversion efficiency of 7.9%, which is thus far the highest reported efficiency among solution-processed Sb₂Se₃ solar cells. This simple procedure and efficiency achievement demonstrate the great potential of the hydrothermal deposition process for the fabrication of high-efficiency Sb₂Se₃ solar cells.