Methylammonium, formamidinium and ethylenediamine mixed triple-cation perovskite solar cells with high efficiency and remarkable stability

Abstract

Solar cells with organic–inorganic perovskites as light absorbers are now delivering more than 22% power conversion efficiencies and are comparable to their inorganic counterparts on a laboratory scale. However, their intrinsic instability hinders the commercialization of this promising photovoltaic technique. Herein we introduced the bivalent alkyldiammonium cation ethylenediamine (EDA²⁺) into methylammonium (MA)/formamidinium (FA) lead iodide (MA_0.7FA_0.3PbI₃) to improve its stability, forming a triple cation perovskite (MA_0.7FA_0.3)_1−2xEDA_xPbI₃ as a light absorber layer for planar perovskite solar cells. After delicately tuning the stoichiometric ratio of EDA²⁺ in the cation, PSCs based on the (MA_0.7FA_0.3)_0.97EDA_0.015PbI₃ (x = 1.5%) perovskite yielded a highest power conversion efficiency of 20.01% with negligible hysteresis. More importantly, the devices showed greatly enhanced stability compared to the EDA-free ones. The unencapsulated perovskite solar cells with EDA incorporation retained 96% of their initial efficiencies after 25 days of storage in an ambient atmosphere.