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Brightly photoluminescent phosphor materials based on silicon quantum dots with oxide shell passivation

Chang-Ching Tu, Qifeng Zhang, Lih Y. Lin, and Guozhong Cao

Open Access Open Access

Abstract

We demonstrate silicon-based phosphor materials which exhibit bright photoluminescence from near-infra-red to green. The colloidal composites which are composed of silicon quantum dots (SiQDs) attached on micro-size silicon particles are synthesized by electrochemical etching of silicon wafers and then dispersed in ethanol. Subsequently, isotropic etching by HF/HNO3 mixture controls the size so as the emission wavelength of SiQDs, and forms an oxide passivating shell. The phosphors can further react with alkoxysilanes to form a stable suspension in non-polar solvents for solution-processing. The resulting red-light-emitting SiQD-based phosphors in chloroform exhibit photoluminescence external quantum efficiency of 15.9%. Their thin films can be efficiently excited by InGaN light-emitting diodes and are stable in room condition.

©2011 Optical Society of America

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Figures (3)
Fig. 1
Fig. 1 (a) The normalized PL spectra of near-IR-, red-, orange-, yellow-, yellow-green- and green-light-emitting colloidal SiQD-based phosphor materials in ethanol. (b) The normalized excitation spectra of the red-, orange-, yellow- and yellow-green-light-emitting phosphors measured in (a). (c) The PL spectra and EQEs of the red-light-emitting phosphors passivated with hydrides, hydroxyl groups and TMPS.

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Fig. 2
Fig. 2 (a) and (b) The SEM images of a drop-casted phosphor thin film by low (103 × ) and high (105 × ) magnification, respectively. (c) “UW” painted with the red-light-emitting phosphors on a glass slide.

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Fig. 3
Fig. 3 (a) The PL spectra of colloidal green-light-emitting phosphors before (solid lines) and after oxidation (dot lines). (b) The PL spectra of a mixture of colloidal red- and yellow-green-light-emitting phosphors, where the black- and grey-dot lines represent different mixing ratios. (c) The light spectra from a 405 nm InGaN LED with the red-light-emitting phosphor thin film as light converters, as a function of increasing LED intensity (from the bottom-dash line to the top-solid line).

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