Abstract Efficient energy band alignment of heterojunction layers in colloidal quantum dot (CQD)-based solar cells is a crucial factor to govern the charge transport characteristics and device performance. In this work, we develop novel cascaded-junctions of lead sulfide (PbS) CQD triple layers consisting of an alkylammonium iodide (AMI)-treated PbS bilayer and a 1,3-propanedithiol (PDT)-treated single layer. The two AMIs, i.e. triethylamine hydroiodide (tri-EAHI) and tetraethylammonium iodide (TEAI), are less hindered and have superior passivation performance compared to tetrabutylammonium iodide (TBAI), the most commonly used AMI. In addition, the band positions of the PbS-TEAI and PbS-tri-EAHI layers are deeper by 0.26 and 0.46 eV, respectively, than those of the PbS-PDT layer, and hence the sequential stacking of these three layers enable an effective cascaded band alignment. The various benefits of the improved band alignment such as increased built-in potential, reduced trap states, widened depletion region, enhanced charge transport and suppressed charge recombination lead to a significant improvement in the device parameters, and the best power conversion efficiency of 10.46% is obtained for the cascaded PbS-tri-EAHI/PbS-TEAI/PbS-PDT-based device.

中文翻译：

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PbS 异质结层的级联能带排列可提高 PbS 量子点太阳能电池的性能

摘要 基于胶体量子点 (CQD) 的太阳能电池中异质结层的有效能带排列是控制电荷传输特性和器件性能的关键因素。在这项工作中，我们开发了新型硫化铅 (PbS) CQD 三层级联结，由烷基碘化铵 (AMI) 处理的 PbS 双层和 1,3-丙二硫醇 (PDT) 处理的单层组成。这两种 AMI，即三乙胺氢碘化物 (tri-EAHI) 和四乙基碘化铵 (TEAI) 与最常用的 AMI 相比，受阻较小且具有优异的钝化性能。此外，PbS-TEAI 和 PbS-tri-EAHI 层的能带位置分别比 PbS-PDT 层深 0.26 和 0.46 eV，因此，这三层的顺序堆叠能够实现有效的级联带对齐。改进的能带排列带来的各种好处，如增加内置电位、减少陷阱态、扩大耗尽区、增强电荷传输和抑制电荷复合，导致器件参数显着改善，最佳功率转换效率为 10.46%为基于级联 PbS-tri-EAHI/PbS-TEAI/PbS-PDT 的器件获得。