Ruddlesden–Popper (RP) layered perovskites (with general formula of (RNH₃)₂A_n−1M_nX_3n+1) have drawn tremendous attention due to their excellent ambient stability while retaining promising device performance. However, quasi-2D perovskites with mixed-cation often suffer from severe phase segregation and vertically aligned multiple perovskite phases (with small n phases concentrated on the bottom and large n phases on the top) are usually formed. Here, we report a strategy to suppress vertical phase segregation by using hydrochloric acid (HCl) additive. As a result, homogenous quasi-2D perovskite films with uniform phase distribution and enhanced film quality are successfully obtained via this additive strategy, which is confirmed by PL measurements. With uniform distribution of different n value phases and high-quality film, FA-based quasi-2D perovskite solar cells with an efficiency of 13.16% and excellent stability was fabricated. This strategy paves a way to develop stable and efficient quasi-2D perovskite solar cells by suppressing phase segregation.

Ruddlesden-Popper（RP）层状钙钛矿（通式为（RNH ₃）₂ A _{n -1} M _n X _{3 n +1}）由于其出色的环境稳定性同时又保留了有希望的器件性能而备受关注。但是，具有混合阳离子的准2D钙钛矿通常会遭受严重的相分离，并且通常会形成垂直排列的多个钙钛矿相（小n相集中在底部，大n相集中在顶部）。在这里，我们报告一种通过使用盐酸（HCl）添加剂抑制垂直相偏析的策略。结果，通过这种添加策略成功地获得了具有均匀相分布和增强膜质量的均质准2D钙钛矿膜，这通过PL测量得到了证实。通过不同n值相的均匀分布和高质量薄膜，制造出效率为13.16％且稳定性极佳的基于FA的准2D钙钛矿型太阳能电池。