Natural methionine-passivated MAPbI 3 perovskite films for efficient and stable solar devices

Defects located at the surfaces and grain boundaries of solution-processed perovskite films serve as nonradiative recombination centers and are detrimental for the photovoltaic performance of solar devices. Herein, a natural amino acid molecule methionine (Met) is selected as an effective passivation agent to enhance the optoelectronic properties of methylammonium lead iodide (MAPbI 3 ) films. The incorporation of a small amount of Met significantly reduces the trap-state density, contributing to longer carrier lifetime of the perovskite films. As a result, solar cells made of Met-mediated perovskite films deliver a high photovoltage of 1.145 V, which is up to 100 mV higher than the control device. In addition, the Met-mediated device exhibits enhanced stability due to the reduced trap states and the improved hydrophobic property of the modified perovskite film, which retains ~ 85% of their initial efficiency after 480-h storage. Graphical abstract The effective methionine passivation is reported, which significantly reduces the trap-state density and leads to longer carrier lifetime of the perovskite films. Methionine-mediated device produces a champion efficiency of 20.13%, with enhanced moisture stability.