Ultraviolet saturable absorption and ultrafast carrier dynamics in ultrasmall black phosphorus quantum dots.
Understanding the photoexcited carrier-relaxation actions in ultrasmall black phosphorus quantum dots (BPQDs) will play a crucial role in the fields of electronics and optoelectronics. Herein, we report the ultraviolet (UV) saturable absorption and ultrafast photoexcited carrier-relaxation dynamics of BPQDs. The ultrasmall BPQDs are synthesized using a facile liquid-exfoliation method and possess a diameter of 3.8 ± 0.6 nm and a thickness of 1.5 ± 0.4 nm. Femtosecond open-aperture (OA) Z-scan measurements showed typical saturable absorption properties in the UV band. A negative nonlinear optical (NLO) absorption coefficient of -(1.4 ± 0.3) × 10-3cm GW-1and a saturable intensity of 6.6 ± 1.3 GW cm-2were determined. Using a degenerate pump-probe technique, an ultrafast photoexcited carrier-recombination time was observed in the range of 216-305 fs, which was 3 orders of magnitude faster than that of BP nanosheets. Such an ultrafast relaxation component may be attributable to the edge- and step-mediated recombination and was confirmed by our density functional theory (DFT) calculations. This work provides fundamental insight into the underlying mechanism of the photoexcited carrier relaxation dynamic action in BPQDs which can enable UV photonic devices.
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn.
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http://orcid.org/0000-0003-1828-8420
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Wang
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn.
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Liu
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn.
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Zeng
Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, Guangdong, China. xf.yu@siat.ac.cn.
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Huang
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn and School of Science, Hunan University of Technology, Zhuzhou 412007, China.
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Xiao
Institute of Mathematics and Physics, Central South University of Forestry and Technology, Changsha 410004, China.
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JB
Li
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn.
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Long
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn.
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Xiao
Institute of Biomedicine and Biotechnology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, Guangdong, China. xf.yu@siat.ac.cn.
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Yu
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn and Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
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Gao
Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China. sixiao@csu.edu.cn junhe@csu.edu.cn.
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