Facilitate hole transport with thin 2D perovskite capping layer to passivate interface defects of 3D perovskite solar cells using PEABr

Hybrid 2D/3D-perovskites are attracting more interest in the area of organometal halide perovskite solar cells (PSCs) because of their high efficiency and extended environmental stability. The 3D portion in 2D/3D perovskites, serves as an active material with exceptional optoelectronic characteristics (for example excellent light absorption and an extended carrier lifetime), while its 2D counterpart protects against environmental conditions (water and oxygen) and increase the stability of the whole structure. In this study, a hetero-structure 2D/3D is constructed via spin-coating a phenyl-ethyl ammonium bromide (PEABr) solution upon over of (FA0.6MA0.4)PbI3 3D perovskite films. As compared to their 3D analogs, the PSC devices based on optimized 2D/3D hetero-structures display substantial improvements in photovoltaic efficiency due to the passivation of cationic and halide vacancies on the surface of 3D perovskite for better energy level alignments, longer carrier lifetimes, and fewer defects, which facilitate hole transfer and transport to the hole transport layer and reduce interface recombination centers. The extremely-thin film of 2D perovskite on the top of 3D perovskite boots the stability and reduces the crystal imperfection of 3D perovskite. Furthermore, the PEABr-treated perovskite device has a PCE of 20.57% as compared with the control device, which has a PCE of 17.01%.