Small-Molecule Copper Chloride Modulating the Buried Interfaces of Perovskite Solar Cells

In perovskite solar cells (PSCs), tin dioxide (SnO₂) is a highly effective electron transport material. On the other hand, the low intrinsic conductivity of SnO₂, the high trap-state density on the surface and bulk of SnO₂, and inadequate interface contacts between SnO₂ and perovskite significantly impact device performance. Herein, small-molecule copper(II) chloride (CuCl₂) is introduced into the SnO₂ dispersion, which inhibits the agglomeration of SnO₂ colloids and improves the quality of the electron transport layer. Furthermore, the introduction of CuCl₂ optimizes the energy-level array between the ETL and perovskite layer (PVK) and passivates the anion/cation defects in SnO₂, perovskite, and their interface, realizing the systematic modulation of the photoelectronic properties of the ETLs and PVKs as well as the PVK/ETL. As a result, the CuCl₂-opmized PSC exhibits an impressive power conversion efficiency of 23.71%, along with improved stability.