Highly Efficient and Stable FASnI3 Perovskite Solar Cell via Modification with Tetrapotassium Hexacyanoferrate

Sn‐based perovskite material is one of the promising absorption materials due to its low toxicity and narrow bandgap. However, the unsatisfying quality of the perovskite film caused by Sn 2+ oxidation and poor crystal growth greatly hinders the device performance. Herein, a layer of tetrapotassium hexacyanoferrate at the PEDOT:PSS/FASnI 3 interface is introduced, which can minimize the concentration of Sn 4+ , thereby suppressing the defect states in the perovskite film, enhancing the conductivity of the PEDOT:PSS film, and forming well‐matched energy alignment in the device. Consequently, the champion device performance of 8.9% is obtained by the modified device, and the unencapsulated device can keep outstanding stability in N 2 atmosphere.