Plant-Derived l-Theanine for Ultraviolet/Ozone Resistant Perovskite Photovoltaics

As the efficiency of perovskite solar cell has skyrocketed to as high as 25.7%, their stability has become the biggest obstacle to commercialization. Preliminary analyses suggest that additive engineering may be effective in improving both solar cell efficiency and its stability. Herein, the plant-derived natural green additive of l-Theanine (Thea) is selected to improve the crystal quality of the perovskite absorber and obtain high-performance perovskite solar cells (PSCs) with ultraviolet/ozone (UV/O-3) resistance. The characterization results reveal that the C(sic)O group in Thea can effectively inhibit the precipitation of metal Pb-0, passivate undercoordinated Pb2+ ions, and promote the nucleation and crystallization of perovskite. In addition, the combination of the N-H group and I- in the form of a hydrogen bond cooperatively reduce the probability of nonradiative recombination of photogenerated carriers and effectively improves the extraction ability of carriers from perovskite absorber. With the cooperation of C(sic)O and -NH2 groups in Thea, the champion efficiency is improved from 22.29% in the control device to 24.58%. More importantly, Thea significantly alleviates the perovskite phase transition and film decomposition induced by UV/O-3 treatment. The study provides exploratory research for the application of plant-derived green additives in the UV/O-3 resistance field of perovskite photovoltaics.