The effects of crystal structure on the photovoltaic performance of perovskite solar cells under ambient indoor illumination

Abstract

Organic-inorganic hybrid lead halide perovskite materials with the general formula MAPbI3-nBrn (n = 0, 1, 2, and 3) exhibiting a range of crystal structures and a wide range of optical bandgaps are explored for their potential to harvest energy from ambient light sources. The replacement of I− with Br− is found to transform the perovskite crystal structure from the tetragonal for MAPbI3 to the pseudo cubic for MAPbI2Br and MAPbIBr2 and cubic for MAPbBr3 while increasing the optical bandgap from 1.59 eV to 2.31 eV. Photovoltaic cells (PVCs) are constructed using these perovskites and are found to exhibit power conversion efficiencies (PCEs) of 29.83 (MAPbI3), 23.75 (MAPbI2Br), 21.47 (MAPbIBr2), and 19.94% (MAPbBr3) under LED light illumination (1000 lux; ~0.371 mW cm−2), with a record high open-circuit voltage (VOC) of 1.15 V being observed for the MAPbBr3. The effect of crystal structure variation on the charge carrier mobility, trap states, recombination losses, photovoltaic properties, and operational stabilities has been investigated systematically under indoor illumination. Overall, this work provides a clear vision on the influence of perovskite crystal structures upon the photovoltaic properties and shows a pathway to achieve high VOC in perovskite PVCs under low-intensity ambient light sources.