Optimizing surface passivation Unproductive charge recombination at surface defects can limit the efficiency of hybrid perovskite solar cells, but these defects can be passivated by the binding of small molecules. Wang et al. studied three such small molecules—theophylline, caffeine, and theobromine—that bear both carbonyl and amino groups. For theophylline, hydrogen bonding of the amino hydrogen to surface iodide optimized the carbonyl interaction with a lead antisite defect and improved the efficiency of a perovskite cell from 21 to 22.6%. Science, this issue p. 1509 Molecules that bring N-H and C=O groups into an optimal configuration passivate antisite lead defects on perovskite surfaces. Surface trap–mediated nonradiative charge recombination is a major limit to achieving high-efficiency metal-halide perovskite photovoltaics. The ionic character of perovskite lattice has enabled molecular defect passivation approaches through interaction between functional groups and defects. However, a lack of in-depth understanding of how the molecular configuration influences the passivation effectiveness is a challenge to rational molecule design. Here, the chemical environment of a functional group that is activated for defect passivation was systematically investigated with theophylline, caffeine, and theobromine. When N-H and C=O were in an optimal configuration in the molecule, hydrogen-bond formation between N-H and I (iodine) assisted the primary C=O binding with the antisite Pb (lead) defect to maximize surface-defect binding. A stabilized power conversion efficiency of 22.6% of photovoltaic device was demonstrated with theophylline treatment.

中文翻译：

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钙钛矿光伏表面缺陷钝化的建设性分子构型

优化表面钝化表面缺陷处的非生产性电荷复合会限制混合钙钛矿太阳能电池的效率，但这些缺陷可以通过小分子的结合钝化。王等人。研究了三种这样的小分子——茶碱、咖啡因和可可碱——同时带有羰基和氨基。对于茶碱，氨基氢与表面碘化物的氢键结合优化了羰基与铅反位缺陷的相互作用，并将钙钛矿电池的效率从 21% 提高到 22.6%。科学，这个问题 p。1509 将 NH 和 C=O 基团带入最佳配置的分子钝化钙钛矿表面上的反位铅缺陷。表面陷阱介导的非辐射电荷复合是实现高效金属卤化物钙钛矿光伏的主要限制。钙钛矿晶格的离子特性通过官能团和缺陷之间的相互作用实现了分子缺陷钝化方法。然而，缺乏对分子构型如何影响钝化效果的深入了解是对合理分子设计的挑战。在这里，用茶碱、咖啡因和可可碱系统地研究了为缺陷钝化而激活的官能团的化学环境。当 NH 和 C=O 在分子中处于最佳构型时，NH 和 I（碘）之间的氢键形成有助于初级 C=O 与反位点 Pb（铅）缺陷结合，从而最大限度地结合表面缺陷。茶碱处理证明了光伏器件的稳定功率转换效率为 22.6%。