Low bandgap tin–lead iodide perovskites are key components of all-perovskite tandem solar cells, but can be unstable because tin is prone to oxidation. Here, to avoid a reaction with the most popular hole contact, we eliminated polyethylenedioxythiophene:polystyrenesulfonate as a hole transport layer and instead used an upward band offset at an indium tin oxide–perovskite heterojunction to extract holes. To suppress oxidative degradation, we improved the morphology to create a compact and large-grained film. The tin content was kept at or below 50% and the device capped with a sputtered indium zinc oxide electrode. These advances resulted in a substantially improved thermal and environmental stability in a low bandgap perovskite solar cell without compromising the efficiency. The solar cells retained 95% of their initial efficiency after 1,000 h at 85 °C in air in the dark with no encapsulation and in a damp heat test (85 °C with 85% relative humidity) with encapsulation. The full initial efficiency was maintained under operation near the maximum power point and near 1 sun illumination for over 1,000 h.

低带隙锡铅碘化钙钛矿是全钙钛矿串联太阳能电池的关键组件，但由于锡易于氧化，因此可能不稳定。在这里，为了避免与最流行的空穴接触发生反应，我们取消了聚乙烯二氧噻吩：聚苯乙烯磺酸盐作为空穴传输层的作用，而是在铟锡氧化物-钙钛矿异质结处使用向上的能带偏移来提取空穴。为了抑制氧化降解，我们改善了形貌以形成致密且大颗粒的薄膜。锡含量保持在50％或以下，并用溅射的铟锌氧化物电极覆盖器件。这些进步导致低带隙钙钛矿太阳能电池中的热稳定性和环境稳定性得到显着改善，而又不影响效率。1，之后，太阳能电池保留了其初始效率的95％在黑暗中，无封装，在黑暗中的空气中，在85°C的黑暗环境中000 h，在潮湿加热试验（85°C，相对湿度为85％）中进行封装。在最大功率点附近和1个太阳光照射下运行1000个小时以上，可以保持全部初始效率。