Oriented Perovskite Crystal towards Efficient Charge Transport in FASnI3 Perovskite Solar Cells

Despite a higher power conversion efficiency (PCE) than other lead‐free perovskite solar cells (PSCs) due to intrinsically excellent optoelectronic properties and suitable bandgaps of tin (Sn) perovskites, Sn‐based PSCs still suffer from issues of stability and efficiency for practical applications. Herein, a novel strategy of tuning perovskite crystal orientation toward ≈45° with respect to the substrate by doping 2,3‐diaminopropionic acid monohydrochloride (2,3‐DAPAC) into formamidinium tin iodide (FASnI 3 ) is proposed, which facilitates charge transport in the perovskite film and consequent device performances. In addition, the incorporation of 2,3‐DAPAC into FASnI 3 enables dense and smooth high‐quality perovskite films with less Sn vacancies. Applications of the 2,3‐DAPAC‐treated FASnI 3 films into PSCs acquire a champion PCE of 7.23%, showing 37.2% enhancement compared with 5.27% of the control device. Moreover, the storage stabilities of both perovskite films and PSCs are significantly prolonged with improved film quality.