Two birds with one stone: SmCl₃ modified TiO₂/perovskite interface to enhance the performance of carbon-based perovskite solar cell

Carbon-based organic-inorganic perovskite solar cells (C-PSCs) are low-cost photovoltaic cells. However, the carrier recombination caused by interface defects and the mismatched interface energy level limits the further improvement of the efficiency of C-PSCs. In this work, SmCl3 was introduced as a "double-sided" modifier to achieve interfacial modification. After modified, Cl- passivated the oxygen vacancy defects on the TiO2 surface. Meanwhile, Sm3+ was diffused into the perovskite interface in the form of a concentration gradient, which balanced the non-coordinated Pb2+ and improved the energy level arrangement. Due to good interfacial contact, the reduced interfacial non-radiative recombination, and rapid charge extraction and transport, the optimized C-PSCs efficiency was increased from 11.03 to 13.4%. In addition, the unencapsulated champion PSC remained stable for long-term stability after the sustained attack for 800 h at room temperature of 20% RH. This work proposed a straightforward interface modification strategy to improve the efficiency of C-PSCs.