Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada.
Adv Mater. 2019 Nov;31(48):e1904304. doi: 10.1002/adma.201904304. Epub 2019 Oct 10.
Infrared-absorbing colloidal quantum dots (IR CQDs) are materials of interest in tandem solar cells to augment perovskite and cSi photovoltaics (PV). Today's best IR CQD solar cells rely on the use of passivation strategies based on lead iodide; however, these fail to passivate the entire surface of IR CQDs. Lead chloride passivated CQDs show improved passivation, but worse charge transport. Lead bromide passivated CQDs have higher charge mobilities, but worse passivation. Here a mixed lead-halide (MPbX) ligand exchange is introduced that enables thorough surface passivation without compromising transport. MPbX-PbS CQDs exhibit properties that exceed the best features of single lead-halide PbS CQDs: they show improved passivation (43 ± 5 meV vs 44 ± 4 meV in Stokes shift) together with higher charge transport (4 × 10 ± 3 × 10 cm V s vs 3 × 10 ± 3 × 10 cm V s in mobility). This translates into PV devices having a record IR open-circuit voltage (IR V ) of 0.46 ± 0.01 V while simultaneously having an external quantum efficiency of 81 ± 1%. They provide a 1.7× improvement in the power conversion efficiency of IR photons (>1.1 µm) relative to the single lead-halide controls reported herein.
红外吸收胶体量子点（IR CQDs）是串联太阳能电池中用于增强钙钛矿和 cSi 光伏（PV）的材料。目前最好的 IR CQD 太阳能电池依赖于基于碘化铅的钝化策略，但这些策略无法完全钝化 IR CQD 的整个表面。氯化铅钝化的 CQD 显示出改善的钝化效果，但电荷输运性能更差。溴化铅钝化的 CQD 具有更高的电荷迁移率，但钝化效果更差。本文引入了一种混合铅卤化物（MPbX）配体交换，它可以在不影响传输的情况下实现彻底的表面钝化。MPbX-PbS CQD 表现出的特性超过了单铅卤化物 PbS CQD 的最佳特性：它们显示出改善的钝化效果（Stokes 位移为 43 ± 5 meV 比 44 ± 4 meV），同时具有更高的电荷输运性能（迁移率为 4×10 ± 3×10 cm V s 比 3×10 ± 3×10 cm V s）。这转化为 PV 器件具有创纪录的红外开路电压（IR V ）为 0.46 ± 0.01 V，同时具有 81 ± 1%的外部量子效率。与本文报道的单铅卤化物对照物相比，它们对大于 1.1 µm 的红外光子的功率转换效率提高了 1.7 倍。
