Fabrication of perovskite solar cells in ambient air by blocking perovskite hydration with guanabenz acetate salt

The fabrication of perovskite solar cells (PSCs) in ambient air can accelerate their industrialization. However, moisture induces severe decomposition of the perovskite layer, limiting the device efficiency. Here we show that sites near vacancy defects absorb water molecules and trigger the hydration of the perovskite, eventually leading to the degradation of the material. We demonstrate that guanabenz acetate salt eliminates both cation and anion vacancies, blocking the perovskite hydration and allowing the crystallization of a high-quality film in ambient air. With guanabenz acetate salt, we prepare PSCs in ambient air with a certified efficiency of 25.08%. The PSCs without encapsulation maintain around 96% of their initial efficiency after 2,000 hours of ageing in ambient air and after 500 hours of operating at the maximum power point under simulated air mass (AM) 1.5 G solar light in a N2 atmosphere. The encapsulated devices retained 85% of their initial efficiency after 300 hours under damp heat conditions (85 degrees C and 85% relative humidity). The fabrication of perovskite solar cells in ambient air is of interest, but the materials are unstable in the presence of moisture. Yan et al. show that guanabenz acetate salt eliminates vacancy defects that trigger perovskite degradation, enabling 25% efficiency devices to be fabricated in air.