Formamidinium methylammonium lead iodide (FAMAPbI₃) perovskite has been intensively investigated as a potential photovoltaic material because it has higher phase stability than its pure FAPbI₃ perovskite counterpart. However, its power conversion efficiency (PCE) is significantly inferior due to its high density of surface detects and mismatched energy level with electrodes. Herein, a bifunctional passivator, methyl haloacetate (methyl chloroacetate, (MClA), methyl bromoacetate (MBrA)), is designed to reduce defect density, to tune the energy levels and to improve interfacial charge extraction in the FAMAPbI₃ perovskite cell by synergistic passivation of both CO groups and halogen anions. As predicted by modeling undercoordinated Pb²⁺, the MBrA shows a very strong interaction with Pb²⁺ by forming a dimer complex ([C₆H₁₀Br₂O₄Pb]²⁺), which effectively reduces the defect density of the perovskite and suppresses non-radiative recombination. Meanwhile, the Br⁻ in MBrA passivates iodine-deficient defects. Consequently, the MBrA-modified device presents an excellent PCE of 24.29%, an open-circuit voltage (V_oc) of 1.18 V (V_oc loss ≈ 0.38 V), which is one of the highest PCEs among all FAMAPbI₃-based perovskite solar cells reported to date. Furthermore, the MBrA-modified devices without any encapsulation exhibit remarkable long-term stability with only 9% of PCE loss after exposure to ambient air for 1440 h.

中文翻译：

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卤乙酸甲酯-铅二聚体复合物实现稳定的 24.29% 效率 FA0.85MA0.15PbI3 钙钛矿太阳能电池

甲脒甲基铵碘化铅 (FAMAPbI ₃ ) 钙钛矿已作为一种潜在的光伏材料进行了深入研究，因为它比纯 FAPbI ₃ 钙钛矿对应物具有更高的相稳定性。然而，由于其表面检测的高密度和与电极的能级不匹配，其功率转换效率（PCE）明显较差。 在此，一种双功能钝化剂卤代乙酸甲酯（氯乙酸甲酯，（MClA），溴乙酸甲酯（MBrA））旨在通过协同钝化降低缺陷密度，调整能级并改善 FAMAPbI ₃钙钛矿电池中的界面电荷提取CO 基团和卤素阴离子。正如通过对不协调的 Pb ^{2+建模所预测的那样}，MBrA通过形成二聚体络合物（[C ₆ H ₁₀ Br ₂ O ₄ Pb] ^{2+ ）与Pb 2+}表现出非常强的相互作用，这有效地降低了钙钛矿的缺陷密度并抑制了非辐射复合。同时，MBrA 中的 Br ^-钝化了缺碘缺陷。因此，MBrA 改性器件的 PCE 为 24.29%，开路电压 ( V _oc ) 为 1.18 V ( V _{oc损耗 ≈ 0.38 V)，是所有 FAMAPbI 3}中 PCE 最高的器件之一迄今为止报道的基于钙钛矿的太阳能电池。此外，未经任何封装的 MBrA 改性器件在暴露于环境空气 1440 小时后表现出显着的长期稳定性，PCE 损失仅为 9%。