Abstract
The effects of surface passivation on the photoluminescence (PL) properties of CdS nanoparticles oxidized by straightforward H2O2 injection were examined. Compared to pristine cadmium sulfide nanocrystals (quantum efficiency ≅ 0.1%), the surface-passivated CdS nanoparticles showed significantly enhanced luminescence properties (quantum efficiency ≅ 20%). The surface passivation by H2O2 injection was characterized using X-ray photoelectron spectroscopy, X-ray diffraction, and time-resolved PL. The photoluminescence enhancement is due to the two-order increase in the radiative recombination rate by the sulfate passivation layer.
Highlights
Semiconductor nanocrystals or quantum dots have attracted great attention because their optical and electrical properties can be tuned by changing their sizes and surface states [1,2,3,4,5,6]
Photoluminescence (PL) characteristics of semiconductor nanocrystals are strongly dependent on their surface states since a large portion of atoms are located at or near the surface of nanoparticles, forming dangling bonds as main trap states against radiative recombination
Focused on the surface states, various strategies for the enhancement of optical properties in CdS nanocrystals have been developed by employing a core/ shell structure, size-selective photoetching, and surface passivation by reducing agents [7,8,9,10,11,12]
Summary
Semiconductor nanocrystals or quantum dots have attracted great attention because their optical and electrical properties can be tuned by changing their sizes and surface states [1,2,3,4,5,6]. Focused on the surface states, various strategies for the enhancement of optical properties in CdS nanocrystals have been developed by employing a core/ shell structure, size-selective photoetching, and surface passivation by reducing agents [7,8,9,10,11,12]. In this regard, the artificial formation of an oxide layer on the surface of CdS nanocrystals holds great potential for surface passivation and tuning the size of nanocrystals [13]. The correlations of the enhanced PL properties with the quantum dot size, local strain, chemical states, and radiative recombination rates are systematically investigated
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