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CdSe/CdTe II型胶态量子阱中长寿命的单激子、带电激子和双激子
王俊慧, 梁桂杰, 吴凯丰
中国科学院大连化学物理研究所, 分子反应动力学国家重点实验室, 能源材料化学协同创新中心, 大连 116023
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DOI:10.1063/1674-0068/30/cjcp1711206
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基金项目:This work was supported by the start-up funding from Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and the Collaborative Innovation Center of Chemistry for Energy Materials (iChEM-2011).
Long-lived Single Excitons, Trions, and Biexcitons in CdSe/CdTe Type-Ⅱ Colloidal Quantum Wells
Jun-hui Wang, Gui-jie Liang, Kai-feng Wu
State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials(iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
Abstract:
Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential electron transfer processes, which leads to a complicated situation that excited states involves not only excitons (electron-hole pairs) but also multi-excitons and charged excitons. While long-lived excitons can be obtained in various systems (e.g., semiconductor nanocrystals), multi-excitons and charged excitons are typically shorted-lived due to nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the third carrier on a few to hundreds of picoseconds timescale. In this work, we report a study of excitons, trions (an exciton plus an additional charge), and biexcitons in CdSe/CdTe colloidal quantum wells or nanoplatelets. The typeⅡ band alignment effectively separates electrons and holes in space, leading to a single exciton lifetime of 340 ns which is ~2 order of magnitudes longer than that in plane CdSe nanoplatelets. More importantly, the electron-hole separation also dramatically slows down Auger decay, giving rise to a trion lifetime of 70 ns and a biexciton lifetime of 11 ns, among the longest values ever reported for colloidal nanocrystals. The long-lived exciton, trion, and biexciton states, combined with the intrinsically strong light-absorption capability of two-dimensional systems, enable the CdSe/CdTe type-Ⅱ nanoplatelets as promising light harvesters for efficient solar-to-fuel conversion reactions.
Key words:  Solar energy  Excited state lifetime  Exciton  Trion  Biexciton  Type-II quantum wells  Nanoplatelets  Auger recombination