Low temperature method-based evaporation/spray-coating technology for wide bandgap perovskite solar cells

Years of working on perovskite solar cells (PSCs)-based tandem devices and single-junction devices have approved that low annealing temperatures can be beneficial for improving device performances. In this study, pseudo-halogen ion engineering works well in the evaporation/spray-coating method. According to our research, it is has been proven that the addition of formamidine acetate (FAAc) can effectively reduce the annealing temperature from 170 °C to 150 °C, accelerate the maturation process of the perovskite films, and broaden the annealing window. As a result, a perovskite film with homogeneous crystallization and low residual stress is achieved, leading to extended charge carrier lifetimes, elevated photoluminescence quantum yields (PLQY), reduced Urbach energies. The corresponding PSCs were prepared through evaporation/spray-coating method achieves an impressive power conversion efficiency (PCE) of 19.46%, which is the highest efficiency among wide-bandgap (WBG) PSCs fabricated by this method. And the unencapsulated devices exhibit satisfactory stability, retaining 80% of the initial PCE after 600 h of thermal aging at 60 °C and retaining 90% of the initial PCE after 1500 h of 50% humidity aging at 25 °C, respectively.