Acta Chim. Sinica ›› 2015, Vol. 73 ›› Issue (9): 959-964.DOI: 10.6023/A15030216 Previous Articles     Next Articles

Special Issue: 非碳基二维材料



徐伟高a, 赵琰媛a, 申超a, 张俊a, 熊启华a,b   

  1. a 南洋理工大学数理科学学院 新加坡 637371;
    b 南洋理工大学电气与电子工程学院 新加坡 639798
  • 投稿日期:2015-03-30 发布日期:2015-05-19
  • 通讯作者: 熊启华
  • 基金资助:

    项目受新加坡国家研究基金(No. NRF-RF2009-06)、教育部Tier2基金(No. MOE2012-T2-2-086)和南洋理工大学启动基金(No. M58110061)资助.

Phonon-assisted Upconversion Photoluminescence in Monolayer MoSe2 and WSe2

Xu Weigaoa, Zhao Yanyuana, Shen Chaoa, Zhang Juna, Xiong Qihuaa,b   

  1. a Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371;
    b NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798
  • Received:2015-03-30 Published:2015-05-19
  • Supported by:

    Project supported by the Singapore National Research Foundation via a fellowship grant (No. NRF-RF2009-06), Ministry of Education via a Tier 2 grant (No. MOE2012-T2-2-086) and Nanyang Technological University via a start-up grant support (No. M58110061).

Phonon-assisted upconversion photoluminescence is the basis of laser cooling effect in solids. Compared to conventional cooling methods, laser cooling has many advantages such as compactness, high efficiency, free of vibrational disturbance and refrigerant-free, etc. Exploring more semiconducting materials in which a net cooling effect can be observed is an important area among the laser cooling community. Monolayer two-dimensional transition metal dichalcogenides (TMDs) like MoSe2 and WSe2 are direct band gap semiconductors. The perfect crystal structure and high extraction efficiency (due to thickness at atomic level) guarantee them the possibility to be potential candidates for laser cooling. In this work, with a Ti-sapphire tunable laser (pumped by a 532 nm laser), we studied the upconversion photoluminescence and its wavelength-dependence. In detail, we implemented experiments on laser power-dependent photoluminescence intensity, the linearity fitting results (at low power) show that it is a phonon-assisted upconversion photoluminescence process; furthermore, this mechanism is also verified from the temperature-dependent upconversion photoluminescence intensity. Further experiments on the investigation of which kinds of phonons are involved in the upconversion process and its efficiency, as well as the design of a sample structure that is free of background absorbance, are still required to help to tell whether net laser cooling can be achieved, or how it can be achieved in monolayers TMDs.

Key words: monolayer two-dimensional crystals, transition metal dichalcogenides (TMDs), upconversion photoluminescence, laser cooling