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Revealing Crystallization Dynamics and the Compositional Control Mechanism of 2D Perovskite Film Growth by In Situ Synchrotron-Based GIXRD

Quasi-two-dimensional (2D) perovskites promise intrinsically stable solar cell performance. However, the crystal orientation and phase distribution in 2D solution-processed perovskites are difficult to manipulate, which restricts the device efficiency as well as its reproducibility. Here, we simply incorporate potassium ion (K+) into a quasi-2D precursor solution, which can dramatically change the nucleation steps during the perovskite films spin-coating process probed by in situ synchrotron-based grazing incident X-ray diffraction (GIXRD). It is notable that a desired vertically oriented 2D phase without an intermediate compound can be easily formed after spin-coating, which simultaneously reduces the distribution of low-dimensional 2D perovskite phases in association with suppressed trap states. Therefore, the power conversion efficiency of doped 10% K+ 2D perovskite solar cells can yield up to 11.3% as well as long-term stable performance with high reproducibility. This work paves a key path to control...