[8p-A414-1~8] 13.9 Optical properties and light-emitting devices

[8p-A414-6] Band-edge photoluminescence from AgInS₂ colloidal quantum dots by the formation of III-VI semiconductor shells

〇Taro Uematsu¹, Kazutaka Wajima¹, Watcharaporn Hoisang¹, Dharmendar Kumar Sharma², Shuzo Hirata², Takahisa Yamamoto³, Tatsuya Kameyama³, Martin Vacha², Tsukasa Torimoto³, Susumu Kuwabata¹ (1.Osaka Univ., 2.Tokyo Tech., 3.Nagoya Univ.)

Keywords:colloidal quantum dots, silver indium sulfide, core/shell structure

Colloidal semiconductor nanoparticles (quantum dots) have been put into practical use as backlight sources of liquid crystalline displays for commercial TV and smartphones. The narrow-band emission originating band-edge transition is a biggest advantage of quantum dot fluorophores. In such a situation, cadmium (Cd)-free quantum dots are attracting much more attention because many countries are planning to place a ban on Cd usage. Several candidates, represented by III-V and I-III-VI semiconductors, have been proposed so far. Silver indium sulfide (AgInS₂) nanoparticles are one of the Cd-free fluorescent nanoparticles with quantum yield higher than 50%. However, their emission was very broad (FWHM of 250 nm or 400 meV) due to the multiple defect-related transition. In the present study, we have succeeded in generating narrow-band emission (FWHM of 28 nm or 103 meV) from AgInS₂ nanoparticles. A new peak was generated at shorter wavelength side with decreasing the original defect emission by coating them with III-VI semiconductors; indium sulfide (In₂S₃) and gallium sulfide (Ga₂S₃). Optical analyses revealed that the new emission originated from the band edge transition. A STEM observation revealed that the Ga₂S₃ shell was amorphous, which was very surprising because conventional II-VI shells such as CdS and ZnS have been designed putting importance on crystallinity and crystalline matching with core nanoparticles. We hope that these findings open up a new strategy for designing core/shell structures.