Simple Method of Dual Passivation with Efficiency Beyond 20% for Fabricating Perovskite Solar Cells in the Full Ambient Air

In order to further promote the commercial application of perovskite solar cells (PSCs), it is particularly important to fabricate devices in the ambient air condition. Herein, we explore a simple method to reproduce high-efficiency and stable PSCs using the one-step anti-solvent deposition conducted in the full ambient air. NH4Ac (ammonium acetate), which is green and environmentally friendly, is first introduced into an anti-solvent (ethyl acetate) to enhance the photovoltaic performance and stability of devices. NH4+ causes the intermediate phase to undergo a process of cation exchange, thereby delaying crystallization. Ac- makes the additive and A-site cation form hydrogen bonds, which in turn makes the intermediate phase more stable. The dual effects of NH4+ and Ac- delay the crystallization of the perovskite film, reduce the density of defect states, and decrease the non-radiative recombination of carriers. By optimizing the concentration of NH4Ac, a champion power conversion efficiency (PCE) of 20.41% and an average PCE of 19.46 +/- 0.64% are achieved, which is currently one of the highest efficiencies in fabricating PSCs under the full ambient air condition. Furthermore, the corresponding PSCs without encapsulation can maintain 82% of its initial PCE when stored in full ambient air condition (30-40% RH) for 30 days.