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Abstract Mixed cation hybrid perovskites such as Cs x FA 1− x PbI 3 are promising materials for solar cell applications, due to their excellent photoelectronic properties and improved stability. Although power conversion efficiencies (PCEs) as high as 18.16% have been reported, devices are mostly processed by the anti‐solvent method, which is difficult for further scaling‐up. Here, a method to fabricate Cs x FA 1− x PbI 3 by performing Cs cation exchange on hybrid chemical vapor deposition grown FAPbI 3 with the Cs + ratio adjustable from 0 to 24% is reported. The champion perovskite module based on Cs 0.07 FA 0.93 PbI 3 with an active area of 12.0 cm 2 shows a module PCE of 14.6% and PCE loss/area of 0.17% cm −2 , demonstrating the significant advantage of this method toward scaling‐up. This in‐depth study shows that when the perovskite films prepared by this method contain 6.6% Cs + in bulk and 15.0% at the surface, that is, Cs 0.07 FA 0.93 PbI 3 , solar cell devices show not only significantly increased PCEs but also substantially improved stability, due to favorable energy level alignment with TiO 2 electron transport layer and spiro‐MeOTAD hole transport layer, increased grain size, and improved perovskite phase stability.
Jiang et al. (Wed,) studied this question.