Multijunction photovoltaics (PVs) are gaining prominence owing to their superior capability of achieving power conversion efficiencies (PCEs) beyond the radiative limit of single-junction cells^1-8, where improving narrow bandgap tin–lead perovskites is critical for thin-film devices⁹. With a focus on understanding the chemistry of tin–lead perovskite precursor solutions, we herein find that Sn(II) species dominate interactions with precursors and additives and uncover the exclusive role of carboxylic acid in regulating solution colloidal properties and film crystallisation, and ammonium in improving film optoelectronic properties. Materials that combine these two function groups, amino acid salts, considerably improve the semiconducting quality and homogeneity of perovskite films, surpassing the effect of the individual functional groups when introduced as part of separate molecules. Our enhanced tin–lead perovskite layer allows us to fabricate solar cells with PCEs of 23.9, 29.7 (certified 29.26%), and 28.7% for single-, double-, and triple-junction devices, respectively. Our 1-cm² triple-junction devices show PCEs of 28.4% (certified 27.28%). Encapsulated triple-junction cells maintain 80% of their initial efficiencies after 860 h maximum power point tracking in ambient. We further fabricate quadruple-junction devices and obtain PCEs of 27.9% with the highest open-circuit voltage of 4.94 V. This work establishes a new benchmark for multijunction PVs.

多结光伏 （PV） 因其实现超越单结电池辐射极限的功率转换效率 （PCE） 的卓越能力而越来越受到重视^1-8，其中改进窄带隙锡铅钙钛矿对于薄膜器件至关重要⁹。通过了解锡-铅钙钛矿前驱体溶液的化学性质，我们发现 Sn（II） 物质在与前驱体和添加剂的相互作用中占主导地位，并揭示了羧酸在调节溶液胶体性能和薄膜结晶中的独特作用，以及铵在改善薄膜光电性能中的独特作用。结合这两个官能团的材料，氨基酸盐，大大提高了钙钛矿薄膜的半导体质量和均匀性，当作为单独分子的一部分引入时，超过了单个官能团的效果。我们增强的锡铅钙钛矿层使我们能够制造单结、双结和三结器件的 PCE 分别为 23.9、29.7（认证 29.26%）和 28.7% 的太阳能电池。我们的 1 cm² 三结器件的 PCE 为 28.4%（经认证为 27.28%）。在环境温度下 80 小时最大功率点跟踪后，封装的三结电池仍保持 80% 的初始效率。我们进一步制造了四结器件，并在最高开路电压 4.94 V 的情况下获得了 27.9% 的 PCE。这项工作为多结 PV 建立了新的基准。