Multi-junction all-perovskite tandem solar cells are a promising choice for next-generation solar cells with high efficiency and low fabrication cost. However, the lack of high-quality low-bandgap perovskite absorber layers seriously hampers the development of efficient and stable two-terminal monolithic all-perovskite tandem solar cells. Here, we report a bulk-passivation strategy via incorporation of chlorine, to enlarge grains and reduce electronic disorder in mixed tin–lead low-bandgap (~1.25 eV) perovskite absorber layers. This enables the fabrication of efficient low-bandgap perovskite solar cells using thick absorber layers (~750 nm), which is a requisite for efficient tandem solar cells. Such improvement enables the fabrication of two-terminal all-perovskite tandem solar cells with a champion power conversion efficiency of 21% and steady-state efficiency of 20.7%. The efficiency is retained to 85% of its initial performance after 80 h of operation under continuous illumination.

多结全钙钛矿串联太阳能电池是具有高效率和低制造成本的下一代太阳能电池的有前途的选择。然而，缺乏高质量的低带隙钙钛矿吸收体层严重阻碍了高效稳定的两端整体单钙钛矿串联太阳能电池的开发。在这里，我们报告了通过引入氯来进行整体钝化的策略，以扩大晶粒并减少混合的锡铅低带隙（〜1.25 eV）钙钛矿吸收层中的电子无序。这使得能够使用厚的吸收层（〜750 nm）来制造高效的低带隙钙钛矿型太阳能电池，这对于高效的串联太阳能电池来说是必不可少的。这样的改进使得能够制造具有21％的最佳功率转换效率和20.7％的稳态效率的两端全钙钛矿串联太阳能电池。在连续照明下运行80小时后，效率保持其初始性能的85％。