Carrier transport behavior in the perovskite light absorption layer significantly impacts the performance of perovskite solar cells (PSCs). In this work, reduced carrier recombination losses were achieved by the design of a band structure in perovskite materials. An ultrathin (PbI₂/PbBr₂)_n film with a gradient thickness ratio was deposited as the lead halide precursor layer by a thermal evaporation method, and PSCs with a gradient band structure in the perovskite absorption layer were fabricated by a two-step method in ambient atmosphere. For comparison, PSCs with homogeneous perovskite materials of MAPbI₃ and MAPbI_xBr_{3 − x} were fabricated as well. It is found that the gradient type-II band structure greatly reduces the carrier lifetime and enhances the carrier separation efficiency. As a result, the PSCs with a gradient band structure exhibit an average power conversion efficiency of 17.5%, which is 1–2% higher than that of traditional PSCs. This work provides a novel method for developing high-efficiency PSCs.

钙钛矿光吸收层中的载流子传输行为显着影响钙钛矿太阳能电池（PSC）的性能。在这项工作中，通过设计钙钛矿材料的能带结构来减少载流子复合损失。采用热蒸发法沉积梯度厚度比的超薄(PbI ₂ /PbBr ₂ ) _n薄膜作为卤化铅前驱体层，并采用两步法制备了钙钛矿吸收层具有梯度能带结构的PSCs在环境大气中。为了进行比较，还制备了具有均质钙钛矿材料 MAPbI ₃和 MAPbI _x Br _{3 − x}的 PSC。研究发现梯度II型能带结构大大降低了载流子寿命并提高了载流子分离效率。结果，具有梯度能带结构的PSC的平均功率转换效率为17.5%，比传统PSC高1-2%。这项工作为开发高效 PSC 提供了一种新方法。