The mixed caesium and formamidinium lead triiodide perovskite system (Cs_1−xFA_xPbI₃) in the form of quantum dots (QDs) offers a pathway towards stable perovskite-based photovoltaics and optoelectronics. However, it remains challenging to synthesize such multinary QDs with desirable properties for high-performance QD solar cells (QDSCs). Here we report an effective oleic acid (OA) ligand-assisted cation-exchange strategy that allows controllable synthesis of Cs_1−xFA_xPbI₃ QDs across the whole composition range (x = 0–1), which is inaccessible in large-grain polycrystalline thin films. In an OA-rich environment, the cross-exchange of cations is facilitated, enabling rapid formation of Cs_1−xFA_xPbI₃ QDs with reduced defect density. The hero Cs_0.5FA_0.5PbI₃ QDSC achieves a certified record power conversion efficiency (PCE) of 16.6% with negligible hysteresis. We further demonstrate that the QD devices exhibit substantially enhanced photostability compared with their thin-film counterparts because of suppressed phase segregation, and they retain 94% of the original PCE under continuous 1-sun illumination for 600 h.

量子点 (QD) 形式的混合铯和甲脒三碘化铅钙钛矿系统 (Cs _{1 - x} FA _x PbI _{3 ) 为实现稳定的基于钙钛矿的光伏和光电子学提供了途径。}然而，合成具有高性能量子点太阳能电池（QDSCs）所需特性的多量子点仍然具有挑战性。在这里，我们报告了一种有效的油酸 (OA) 配体辅助阳离子交换策略，该策略允许在整个组成范围内可控合成 Cs _{1 - x} FA _x PbI _{3 QD (} x  = 0-1），这在大晶粒多晶薄膜中是无法获得的。在富含 OA 的环境中，促进了阳离子的交叉交换，从而能够快速形成具有降低缺陷密度的 Cs _{1 - x} FA _x PbI _{3量子点。}英雄 Cs _0.5 FA _0.5 PbI ₃ QDSC 实现了 16.6% 的认证记录功率转换效率 (PCE)，滞后可忽略不计。我们进一步证明，由于相分离受到抑制，与薄膜对应物相比，QD 器件表现出显着增强的光稳定性，并且在连续 1 日光照 600 小时下，它们保留了原始 PCE 的 94%。