Open Access Nano Express

Temperature and composition dependent excitonic luminescence and exciton-phonon coupling in CdSeS nanocrystals

Wenzhi Wu1, Dongqi Yu2, Hong-an Ye1, Yachen Gao1 and Qing Chang1*

Author affiliations

1 School of Electronic Engineering, Heilongjiang University, Harbin 150080, Peoples Republic of China

2 School of Physics and Electronic Technology, Liaoning Normal University, Dalian, 116029, Peoples Republic of China

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Citation and License

Nanoscale Research Letters 2012, 7:301  doi:10.1186/1556-276X-7-301

Published: 8 June 2012

Abstract

The yellow- and red-emitting CdSeS nanocrystals (NCs) synthesized through one-step organometallic synthesis method are uniformly assembled in polymethyl methacrylate (PMMA). A higher-energy emission band originates from band-edge excitonic state appeared at low temperature. With the Se dopant concentration increasing, the luminescent spectra of CdSeS NCs have a red-shifted emission peak and a shorter luminescent lifetime, which is attributed to the existence of trapping state caused by surface defect and Se dopant. CdSeS NC shows a shorter luminescence lifetime and higher energy emission peak in PMMA matrix than that in toluene, indicating that the former is more favorable to transfer energy through exciton-phonon coupling. The upconversion luminescence (UCL) is observed using 800 nm femtosecond laser excitation. The pump power dependence demonstrated UCL spectra of yellow-emitting CdSeS NCs has a slope of 2.2, while that of red-emitting CdSeS NCs has a slope of 1.4. The results demonstrate that the two-photon absorption plays a dominating role when Se concentration of CdSeS NCs is lower, while phonon-assisted UCL by one-photon excitation gradually takes place with the amount of Se dopants increasing.

Keywords:
71.35.Aa; 71.55.Gs; 78.47.jd; 78.67.Hc.