Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 12, Issue 49, Pages 11931-11938Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.1c03478
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Funding
- National Natural Science Foundation of China [11904172]
- Natural Science Foundation of Jiangsu Province [BK20190446]
- Nanjing University of Science and Technology
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The study investigates the spectral and dynamic properties of heavy-metal-free ZnSeTe-based CQDs, decoding carrier trapping processes and revealing the relationship between them and the spectral composition in the range of 470-525 nm. Through shell engineering, the CQDs demonstrate high quantum efficiency and show potential as blue-green emitters for optoelectronic applications like white light-emitting diodes.
Developing non-toxic and high-performance colloidal semiconductor quantum dots (CQDs) represents the inevitable route toward CQD-enabled technologies. Herein, the spectral and dynamic properties of heavy-metal-free ZnSeTe-based CQDs are investigated by transient absorption spectroscopy and theoretical modeling. We for the first time decode the ultrafast hot carrier trapping (<2 ps) and band-edge carrier trapping processes (similar to 6 ps) in the CQD system, which plagues the emission performance. The ZnSe/ZnSeS/ZnS shell engineering greatly suppresses the non-radiative trapping process and results in a high photoluminescence quantum yield of 88%. We demonstrate that the core/shell nano-heterostructure forms the quasi-type II configuration, in contrast to the presumed type I counterpart. Moreover, the Auger recombination and hot carrier cooling processes are revealed to be similar to 454-405 ps and 160-370 fs, respectively, and their relationship with the composition in the spectral range of 470-525 nm is clarified. The above merits render these ZnSeTe CQDs as outstanding blue-green emitters for optoelectronic applications, exemplified by the white light-emitting diodes.
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