Strengthened cathode interface using an ultrathin 2D ferroelectric semiconductor for inverted perovskite solar cells

Abstract

Cathode interface is of prime importance for inverted perovskite solar cells (PSCs) as interface characteristics play a vital role in overall device performance. Herein, we found that such interface characteristics can be efficiently strengthened by applying an ultrathin 2D ferroelectric semiconductor, α-In₂Se₃, as a cathode buffer layer (CBL). Owing to its intrinsic ferroelectric nature, the explored α-In₂Se₃ CBL tends to be spontaneously polarized at room temperature in an out-of-plane orientation. This polarization direction is perpendicular to the cathode interface, i.e., the PCBM/Ag interface, thus providing an extra polarization electric field to reduce the interface energy barrier to form an ohmic electron contact. Combining this merit with excellent electrical conductivity, interface-mediated charge accumulation and recombination is significantly reduced, boosting the efficiency of the α-In₂Se₃-based device up to 24.51% with substantially improved long term stability. This work demonstrates an effective way to strengthen interface characteristics using an ultrathin 2D ferroelectric semiconductor.