Ionic Effect Enhances Light Emission and the Photovoltage of Methylammonium Lead Bromide Perovskite Solar Cells by Reduced Surface Recombination

Abstract

The achievement of optimal power conversion efficiencies (PCEs) in wide-band-gap perovskite solar cells (PSCs) is delayed by photovoltage losses associated with poor understanding of recombination dynamics. In this work, we use high-quality methylammonium lead bromide perovskite solar cells with selective contacts treated with lithium-containing additives to investigate recombination mechanisms. By comparison of the photovoltaic performance of devices we confirm that the presence of this additive in the electron selective layer (ESL) significantly increases the open-circuit potential to values of 1.58 V. Impedance spectroscopy coupled with electroluminescence and photoluminescence analysis reveals that lithium ions present at the mesoporous TiO2 layer dramatically enhances the radiative recombination in the perovskite by reduction of undesired nonradiative and surface recombination pathways. This work highlights that the employ of additives helps to modify the electronic charge distribution at the metal oxide/perovskite interface to suppress undesired recombination mechanisms.