Photochemical Shield Enabling Highly Efficient Perovskite Photovoltaics

Abstract Oxygen is difficult to be physically removed. Oxygen will be excited by light to form free radicals which further attack the lattice of perovskite. The stabilization of α‐FAPbI 3 against δ‐FAPbI 3 is the key to optimize perovskite solar cells. Herein, the simple molecule, benzaldehyde (BAH) is adopted. The photochemical shield will be established in perovskite layer. Moreover, heterogeneous nucleation induced by BAH enhances the crystallization of α‐FAPbI 3 . Consequently, the stability of device is improved significantly. The target device maintains 95% of original power conversion efficiency after 1500 h under air conditions and light‐emitting diode light. The power conversion efficiency increases from 23.21% of pristine device to 24.82% of target device.