The surface chemistry of colloidal quantum dots (CQD) play a crucial role in fabricating highly efficient and stable solar cells. However, as‐synthesized PbS CQDs are significantly off‐stoichiometric and contain inhomogeneously distributed S and Pb atoms at the surface, which results in undercharged Pb atoms, dangling bonds of S atoms and uncapped sites, thus causing surface trap states. Moreover, conventional ligand exchange processes cannot efficiently eliminate these undesired atom configurations and defect sites. Here, potassium triiodide (KI₃) additives are combined with conventional PbX₂ matrix ligands to simultaneously eliminate the undercharged Pb species and dangling S sites via reacting with molecular I₂ generated from the reversible reaction KI₃ ⇌ I₂ + KI. Meanwhile, high surface coverage shells on PbS CQDs are built via PbX₂ and KI ligands. The implementation of KI₃ additives remarkably suppresses the surface trap states and enhances the device stability due to the surface chemistry optimization. The resultant solar cells achieve the best power convention efficiency of 12.1% and retain 94% of its initial efficiency under 20 h continuous operation in air, while the control devices with KI additive deliver an efficiency of 11.0% and retains 87% of their initial efficiency under the same conditions.

中文翻译：

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通过化学结合优化 PbS 胶体量子点的表面化学以实现高效稳定的太阳能电池

胶体量子点（CQD）的表面化学在制造高效、稳定的太阳能电池中发挥着至关重要的作用。然而，所合成的 PbS CQD 明显偏离化学计量，并且表面含有不均匀分布的 S 和 Pb 原子，这导致 Pb 原子带电不足、S 原子的悬挂键和无帽位点，从而导致表面陷阱态。此外，传统的配体交换过程不能有效地消除这些不需要的原子构型和缺陷位点。在此，三碘化钾 (KI _{3 ) 添加剂与传统的 PbX 2}基质配体结合，通过与可逆反应 KI ₃  ⇌ I _{2 + KI 产生的分子 I 2}反应，同时消除带电不足的 Pb 物种和悬挂的 S 位点 。同时，PbS CQD 上的高表面覆盖率壳是通过 PbX ₂和 KI 配体构建的。_{由于表面化学优化，KI 3}添加剂的使用显着抑制了表面陷阱态并增强了器件稳定性。所得太阳能电池的最佳功率转换效率为12.1%，在空气中连续工作20小时后仍保留其初始效率的94%，而添加KI添加剂的控制装置的效率为11.0%并保留其初始效率的87%相同条件下。