Deciphering exciton-generation processes in quantum-dot electroluminescence

Yunzhou Deng, Xing Lin, Wei Fang, Dawei Di, Linjun Wang, Richard H. Friend, Xiaogang Peng and Yizheng Jin ()
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Yunzhou Deng: Zhejiang University
Xing Lin: Zhejiang University
Wei Fang: Zhejiang University
Dawei Di: International Research Center for Advanced Photonics, Zhejiang University
Linjun Wang: Zhejiang University
Richard H. Friend: University of Cambridge
Xiaogang Peng: Zhejiang University
Yizheng Jin: Zhejiang University

Nature Communications, 2020, vol. 11, issue 1, 1-8

Abstract: Abstract Electroluminescence of colloidal nanocrystals promises a new generation of high-performance and solution-processable light-emitting diodes. The operation of nanocrystal-based light-emitting diodes relies on the radiative recombination of electrically generated excitons. However, a fundamental question—how excitons are electrically generated in individual nanocrystals—remains unanswered. Here, we reveal a nanoscopic mechanism of sequential electron-hole injection for exciton generation in nanocrystal-based electroluminescent devices. To decipher the corresponding elementary processes, we develop electrically-pumped single-nanocrystal spectroscopy. While hole injection into neutral quantum dots is generally considered to be inefficient, we find that the intermediate negatively charged state of quantum dots triggers confinement-enhanced Coulomb interactions, which simultaneously accelerate hole injection and hinder excessive electron injection. In-situ/operando spectroscopy on state-of-the-art quantum-dot light-emitting diodes demonstrates that exciton generation at the ensemble level is consistent with the charge-confinement-enhanced sequential electron-hole injection mechanism probed at the single-nanocrystal level. Our findings provide a universal mechanism for enhancing charge balance in nanocrystal-based electroluminescent devices.

Date: 2020
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DOI: 10.1038/s41467-020-15944-z

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