Two-dimensional (2D)/quasi-2D perovskite solar cells (PSCs) incorporating organic spacer cations exhibit appealing ambient stability in comparison with their 3D analogs. Most reported organic spacer cations are based on ammonium, whereas formamidinium (FA⁺) has been seldom applied despite that FA has been extensively used in high-efficiency 3D PSCs. Herein, a novel FA-based organic spacer cation, 4-chloro-phenylformamidinium (CPFA⁺), is applied in quasi-2D Ruddlesden-Popper (RP) PSCs for the first time, and methylammonium chloride (MACl) is employed to promote crystal growth and orientation of perovskite film, resulting in high power conversion efficiency (PCE) with improved stability. Upon incorporating CPFA⁺ organic spacer cation and MACl additive, high-quality quasi-2D CPFA₂MA_n−1Pb_n(I_0.857Cl_0.143)_3n+1 (n=9) perovskite film forms, exhibiting improved crystal orientation, reduced trap state density, prolonged carrier lifetime and optimized energy level alignment. Consequently, the CPFA₂MA_n−1Pb_n(I_0.857Cl_0.143)_3n+1 (n=9) quasi-2D RP PSC devices deliver a highest PCE of 14.78%. Moreover, the un-encapsulated CPFA-based quasi-2D RP PSC devices maintain ∼80% of its original PCE after exceeding 2000 h storage under ambient condition, whereas the 3D MAPbI₃ counterparts retain only ∼45% of its original PCE. Thus, the ambient stability of quasi-2D RP PSC devices is improved obviously relative to its 3D MAPbI₃ counterpart.

与 3D 类似物相比，包含有机间隔阳离子的二维 (2D)/准 2D 钙钛矿太阳能电池 (PSC) 表现出吸引人的环境稳定性。大多数报道的有机间隔阳离子基于铵，而甲脒 (FA ⁺ ) 很少应用，尽管 FA 已广泛用于高效 3D PSC。在此，新型 FA 基有机间隔阳离子 4-氯-苯基甲脒 (CPFA ⁺ )首次应用于准二维 Ruddlesden-Popper (RP) PSC，并采用甲基氯化铵 (MACl) 促进结晶。钙钛矿薄膜的生长和取向，从而获得高功率转换效率（PCE）并提高稳定性。加入 CPFA ^{+ 后}有机间隔阳离子和 MACl 添加剂，高质量准二维 CPFA ₂ MA _{n -1} Pb _n (I _0.857 Cl _0.143 ) _{3 n +1} ( n =9) 钙钛矿薄膜形式，表现出改善的晶体取向，降低的陷阱态密度，延长载流子寿命并优化能级对齐。因此，CPFA ₂ MA _{n -1} Pb _n (I _0.857 Cl _0.143 ) _{3 n +1} ( n=9) 准 2D RP PSC 设备提供 14.78% 的最高 PCE。此外，未封装的基于 CPFA 的准 2D RP PSC 器件在环境条件下存储超过 2000 小时后仍保持其原始 PCE 的约 80%，而 3D MAPbI ₃对应物仅保留其原始 PCE 的约 45%。因此，准 2D RP PSC 器件的环境稳定性相对于其 3D MAPbI ₃对应物明显提高。