Synthesis of Cu-In-S Fluorescent Nanocrystals
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1064-PP03-19
Synthesis of Cu-In-S Fluorescent Nanocrystals Kosuke Watanabe1, Masato Uehara2, Hiroyuki Nakamura2, and Hideaki Maeda2,3 1 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1, Kasugakoen, Kasuga, Fukuoka, 816-8580, Japan 2 Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 807-1, Shuku-machi, Tosu, Saga, 841-0052, Japan 3 Japan Science and Technology Agency, CREST, 4-1-8, Hon-chou, Kawaguchi, Saitama, 3320012, Japan ABSTRACT CuInS2 (CIS) fluorescent nanocrystals (NCs) were obtained by heating an organic metal complex. The photoluminescence (PL) originated from the donor-acceptor, and the quantum yield (QY) was achieved at 6%. Furthermore, we doped some metal ions (Zn2+, Cd2+ or Ag+) by the post heat-treatment in the organic coordinating solvent in order to tune the band gap of NCs. By this post treatment, the alteration of NCs structure was suggested, such as changing into an alloying and composite structure. In Zn-doping, the PL wavelength was widely tuned from 535 to 650 nm by alloying between CIS and ZnS. Moreover, PL intensity was increased with these structure alterations. In particular, the materials doped with Zn or Cd achieved respective QY of 25% and 40%. INTRODUCTION Semiconductor nanocrystals (NCs) have received much attention due to their many applications particularly as fluorescence tags for biological molecules [1], and as tunable LEDs. The colloidal II-VI type semiconductor NCs are easily produced in organic solvent because they favor ionic bonding. However, II-VI type semiconductor NCs (for example, CdSe, CdTe and HgS) with emission at the visible and near-infrared regions include toxic elements (Cd and Hg) which are unregulated by “Restriction of the Use of Certain Hazardous Substances (RoHS)” and “Waste Electrical and Electronic Equipment (WEEE)”. Therefore, we focused on the chalcopyrite materials as an alternative material. Chalcopyrite I-III-VI2 semiconductors are direct transition semiconductors that favor ionic bonding similar to II-VI type materials. Moreover, chalcopyrite materials have a wider range of choices for elements. CuInS2 (CIS) has a band gap energy (Eg) of 1.5 eV and is expected to show the photoluminescence (PL) in the visible range to near-infrared range by quantum effect. The purpose of this study is to synthesize highly luminescent CIS NCs and to tune their PL wavelength. To the best of our knowledge, the QY of reported CIS NCs were about 5% [2] and high luminescent CIS NCs have not been reported. The reports on wide tuning of PL wavelength are limited. In the previous paper, we tuned the PL wavelength from 550 nm to 800 nm by the alloying with ZnS, but the QY was not high (~5%) [3]. In this study, we synthesized CIS fluorescent NCs of high QY by heating an organic metal complex, and obtained slightly higher luminescent NCs by alteration of the sulfur source compared with the previous report. Moreover, we tried to alter the band gap by alloying another material in order to tun
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