Graphene-covered perovskites: an effective strategy to enhance light absorption and resist moisture degradation

Abstract

The long-term stability of methylammonium lead triiodide (MAPbI₃) perovskite in moist environments is a paramount challenge to realise the commercialization of perovskite solar cells. In an attempt to address this concern, we have carried out systematic first-principles studies on the MAPbI₃ perovskite with a hydrophobic graphene layer interfaced as a water barrier. We find there is a charge transfer at the graphene/MAPbI₃ interface and electrons can be excited from graphene into the perovskite surface, leading to well separated electron–hole pairs, i.e. reduced recombination. By studying the optical properties, we find the hybrid graphene/MAPbI₃ nanocomposite displays enhanced light absorption compared with the pristine MAPbI₃. Furthermore, from an ab initio molecular dynamics simulation, the graphene/MAPbI₃ nanocomposite is confirmed to be able to resist the reaction with water molecules, highlighting a great advantage of this nanocomposite in promoting long-term photovoltaic performance.