Perovskite tandem solar cells show promising performance, but non-radiative recombination and its progressive worsening with time, especially in the mixed Sn–Pb low-bandgap layer, limit performance and stability. Here we find that mixed Sn–Pb perovskite thin films exhibit a compositional gradient, with an excess of Sn on the surface—and we show this gradient exacerbates oxidation and increases the recombination rate. We find that diamines preferentially chelate Sn atoms, removing them from the film surface and achieving a more balanced Sn:Pb stoichiometry, making the surface of the film resistive to the oxidation of Sn. The process forms an electrically resistive low-dimensional barrier layer, passivating defects and reducing interface recombination. Further improving the homogeneity of the barrier layer using 1,2-diaminopropane results in more uniform distribution and passivation. Tandems achieve a power conversion efficiency of 28.8%. Encapsulated tandems retain 90% of initial efficiency following 1,000 h of operating at the maximum power point under simulated one-sun illumination in air without cooling.

钙钛矿串联太阳能电池显示出良好的性能，但非辐射复合及其随时间逐渐恶化，特别是在混合 Sn-Pb 低带隙层中，限制了性能和稳定性。在这里，我们发现混合 Sn-Pb 钙钛矿薄膜表现出成分梯度，表面上有过量的 Sn，并且我们发现这种梯度会加剧氧化并增加复合率。我们发现二胺优先螯合Sn原子，将其从薄膜表面去除并实现更平衡的Sn:Pb化学计量，使得薄膜表面能够抵抗Sn的氧化。该工艺形成电阻性低维势垒层，钝化缺陷并减少界面复合。使用 1,2-二氨基丙烷进一步改善阻挡层的均匀性，导致更均匀的分布和钝化。 Tandems实现了28.8%的功率转换效率。在空气中模拟单太阳光照下，在最大功率点运行 1,000 小时后，封装串联串联器件仍保持 90% 的初始效率，无需冷却。