Intermediate Phase Engineering for Efficient and Stable All-Inorganic Perovskite Solar Cells

The serious carrier recombination in all-inorganic perovskite solar cells (PSCs) is the key factor limiting their efficiency. Residual stress and defects arising from the fabrication process can significantly affect carrier transport, recombination kinetics, activation energy for ion migration, and ultimately the efficiency and stability of PSCs. Herein, the inorganic additive ammonium halide was introduced into the precursor solution to form the NH4Pb2Br5 intermediate phase and regulate the nucleation and crystallization of the film through the interaction of ammonium and chlorine groups with CsPbBr3 crystals. As a result of stress relaxation and simultaneous defect passivation of the perovskite films, the top-performing PSC displays an impressive efficiency of 10.61%, with an ultrahigh open-circuit voltage of 1.650 V. Notably, the device also exhibits significantly improved stability against prolonged exposure to persistent humidity (80% RH) and heat (80 °C) over 120 days.