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Letter

Surface Treatment to Enhance the Quantum Efficiency of Semiconductor Nanocrystals

Supporting Info

Eunjoo Jang,*^† Shinae Jun,^† Youngsu Chung,^‡ and Lyongsun Pu^†

Electronic Materials Laboratory and Analytical Engineering Laboratory, Samsung Advanced Institute of Technology, Mt.14-1, Nongseo-Ri, Giheung-Eup, Yongin-Si, Gyeonggi-Do, 449-712 Korea

J. Phys. Chem. B, 2004, 108 (15), pp 4597–4600

DOI: 10.1021/jp049475t

Publication Date (Web): March 24, 2004

Corresponding author. Phone: 82-31-280-6753. Fax: 82-31-280-6725. E-mail: ejjang12@samsung.com.

†

Electronic Materials Laboratory.

‡

Analytical Engineering Laboratory.

Abstract

The photoluminescence quantum efficiency of semiconductor nanocrystals at room temperature was markedly enhanced about 50 times by surface treatment of the nanocrystals after synthesis, and the original photoluminescence peak position and narrow line width were maintained. Simply, the nanocrystal surface was treated with a small amount of sodium borohydride (NaBH₄) in toluene at room temperature. The surface-treated nanocrystals showed very high quantum efficiency, up to 75%, even in the blue region of 490 nm. The TGA and XPS data revealed that some of the surfactants on the nanocrystal surface were removed by the reaction with NaBH₄ and that the exposed cadmium on the surface was converted to cadmium oxide. The cadmium oxide functioned as a robust passivation layer on the CdS surface and contributed more electron density toward the inside of the CdS core to enhance exciton recombination. The surface treatment was powerfully effective in improving the quantum efficiency of II−VI compound semiconductors such as CdS, CdSe, and CdTe, and generally their mixture-type nanosized materials synthesized under a variety of conditions.

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