Enhancement on charge transfer properties of CuSbS quantum dots hole transport materials by surface ligand modulation in perovskite solar cells

Colloidal quantum dots (QDs) have been considered as novel hole transport materials (HTMs) for perovskite solar cells (PSCs). Optimizing the surface state of QDs can provide higher current density and better stability. In this work, the original ligand (oleylamine) on the surface of Cu 12 Sb 4 S 13 QDs is first replaced with trimethylammonium hydroxide and then with 3-mercaptopropionic acid through a two-step process, which exhibits better optical property and higher quality. Meanwhile, pure short chain ligand (3-mercaptopropionic acid) capped Cu 12 Sb 4 S 13 QDs can provide an excellent charge transfer pathway when used as a hole transport layer of perovskite solar cells. As a result, PSCs based on the Cu 12 Sb 4 S 13 QDs HTMs prepared by a two-step ligand-exchange process exhibited higher current density than devices based on spiro-OMeTAD, which enhanced the photovoltaic conversion efficiency from 14.65% to 15.43%. A two-step surface ligand-exchange process has been introduced for Cu 12 Sb 4 S 13 QDs hole transport materials, which effectively enhanced the photovoltaic conversion efficiency of perovskite solar cells from 14.65% to 15.43%.