Electric-field-manipulated crystal stacking for high-quality organic–inorganic halide perovskites

An external electric field (EEF) was applied to regulate perovskite crystal growth in order to achieve the preferred crystallization. The out-of-plane and in-plane crystallization of MAPbI 3-x Cl x , MAPbI 3 and Cs 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 perovskites was compared based on the grazing incidence X-ray diffraction technique. The results showed that vertical EEF stretches the perovskite crystals, making them exhibit vertical preferential growth on the substrate while shortening the lateral stacking spacing. Although the upward and downward EEF directions showed a similar regulatory effect on crystallization, they exhibited opposing effects on the built-in field in a photovoltaic device. This work reveals the mechanism of perovskite crystal stacking under an external field.