Wang Junhui, Ding Tao, Gao Kaimin, Wang Lifeng, Zhou Panwang, Wu Kaifeng
State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, Liaoning, China.
University of the Chinese Academy of Sciences, 100049, Beijing, China.
Nat Commun. 2021 Nov 3;12(1):6333. doi: 10.1038/s41467-021-26705-x.
A key process underlying the application of low-dimensional, quantum-confined semiconductors in energy conversion is charge transfer from these materials, which, however, has not been fully understood yet. Extensive studies of charge transfer from colloidal quantum dots reported rates increasing monotonically with driving forces, never displaying an inverted region predicted by the Marcus theory. The inverted region is likely bypassed by an Auger-like process whereby the excessive driving force is used to excite another Coulomb-coupled charge. Herein, instead of measuring charge transfer from excitonic states (coupled electron-hole pairs), we build a unique model system using zero-dimensional quantum dots or two-dimensional nanoplatelets and surface-adsorbed molecules that allows for measuring charge transfer from transiently-populated, single-charge states. The Marcus inverted region is clearly revealed in these systems. Thus, charge transfer from excitonic and single-charge states follows the Auger-assisted and conventional Marcus charge transfer models, respectively. This knowledge should enable rational design of energetics for efficient charge extraction from low-dimensional semiconductor materials as well as suppression of the associated energy-wasting charge recombination.
低维量子限域半导体在能量转换中的应用所基于的一个关键过程是这些材料的电荷转移，然而，这一过程尚未得到充分理解。对胶体量子点电荷转移的广泛研究表明，电荷转移速率随驱动力单调增加，从未出现过马库斯理论预测的反转区域。反转区域可能被类似俄歇的过程绕过，即过量的驱动力用于激发另一个库仑耦合电荷。在此，我们构建了一个独特的模型系统，使用零维量子点或二维纳米片以及表面吸附分子，来测量从瞬态填充的单电荷态的电荷转移，而不是测量来自激子态（耦合的电子 - 空穴对）的电荷转移。在这些系统中清楚地揭示了马库斯反转区域。因此，从激子态和单电荷态的电荷转移分别遵循俄歇辅助和传统的马库斯电荷转移模型。这一知识应有助于合理设计能量学，以实现从低维半导体材料中高效提取电荷，并抑制相关的能量浪费性电荷复合。
