Narrow-bandgap (NBG) Pb–Sn perovskites are ideal candidates as rear subcell in all-perovskite tandem solar cells. Because Pb–Sn perovskites contain multiple components, the rational regulation of vertical structure and both interfaces of the film is primarily crucial to achieve high-performing NBG perovskite solar cells (PSCs). Herein, a molecule anchoring strategy is developed to in situ construct Cs_0.1MA_0.3FA_0.6Pb_0.5Sn_0.5I₃ perovskite film with vertically aligned crystals and optimized interfaces. Specifically, l-alanine methyl ester is developed as an anchoring additive to induce the vertical crystal growth, while PEA₂PbI₃SCN film is introduced to promote the homogeneous crystallization at the buried interface via SCN− anchoring with cations. Further ethylenediamine dihalides (EDA(I/Cl)₂) post-treatment leads to the gradient energy level alignment on the film surface. Pb–Sn PSCs based on such film show efficient charge transport and extraction, producing a champion power conversion efficiency (PCE) of 22.3% with an impressive fill factor of 82.14%. Notably, combining with semitransparent 1.78 eV wide-bandgap PSCs, the four-terminal all-perovskite tandem device achieves a PCE of 27.1%. This work opens up a new pathway to boost the performance of Pb–Sn PSCs and their tandem devices.

中文翻译：

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分子锚定策略促进高效铅锡钙钛矿太阳能电池和串联器件的垂直均匀结晶和对齐界面


窄带隙（NBG）Pb-Sn钙钛矿是全钙钛矿串联太阳能电池中后部子电池的理想候选者。由于Pb-Sn钙钛矿含有多种成分，垂直结构和薄膜两个界面的合理调控对于实现高性能NBG钙钛矿太阳能电池（PSC）至关重要。在此，开发了一种分子锚定策略来原位构建具有垂直排列晶体和优化界面的Cs _0.1 MA _0.3 FA _0.6 Pb _0.5 Sn _0.5 I ₃钙钛矿薄膜。具体来说，开发了l-丙氨酸甲酯作为锚定添加剂来诱导垂直晶体生长，同时引入PEA ₂ PbI ₃ SCN膜以通过与阳离子的SCN−锚定来促进埋入界面处的均匀结晶。进一步的乙二胺二卤化物（EDA(I/Cl) ₂ ）后处理导致薄膜表面上的梯度能级排列。基于此类薄膜的 Pb-Sn PSC 显示出高效的电荷传输和提取，产生 22.3% 的冠军功率转换效率 (PCE) 和令人印象深刻的 82.14% 的填充因子。值得注意的是，与半透明1.78 eV宽带隙PSC相结合，四端全钙钛矿串联器件的PCE达到27.1%。这项工作为提高 Pb-Sn PSC 及其串联器件的性能开辟了一条新途径。