Cu₁₂Sb₄S₁₃ Quantum Dots with Ligand Exchange as Hole Transport Materials in All-Inorganic Perovskite CsPbI₃ Quantum Dot Solar Cells

Perovskite solar cells (PSCs) have developed rapidly in the past 10 years. However, they are faced with a huge challenge for stability improvement because of the volatile organic components in the light absorption and hole transporting layer. Herein, we fabricate all-inorganic PSCs with the structure of FTO/c-TiO2/m-TiO2/CsPbI3 quantum dots (QDs)/Cu12Sb4S13 QDs/Au to improve device stability. To enhance the photovoltaic performance of PSCs, the surface oleylamine ligands of Cu12Sb4S13 QDs with 3-mercaptopropionic acid are exchanged, as the enhanced electronic coupling and reduced band gap are realized after the ligands exchange. Cu12Sb4S13 QD based PSCs exhibit a PCE of 10.02%, approaching that of the spiro-MeOTAD based PSCs (12.14%). A high short-circuit current density of 18.28 mA cm–2 is achieved because of the enhanced light absorption and excellent hole extraction ability of Cu12Sb4S13 QDs. Moreover, Cu12Sb4S13 QD based PSCs exhibit the improved long-term stability and retain 94% of their initial PCE after storage in ambient air for 360 h.