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HL: Fachverband Halbleiterphysik

HL 42: Quantum Dots and Wires: Optics I

HL 42.4: Vortrag

Mittwoch, 19. März 2025, 17:45–18:00, H17

Studying the optical properties of AgInS2-based quanutm dots — •Yizhuo Xi, Julian Mann, Jochen Feldmann, and Sushant Ghimire — Chair for photonics and optoelectronics, Nano-institute Munich and department of physics, Ludwig-Maximilians-University, Königstr.10, 80539 Munich, Germany

I-III-VI quantum dots have attracted considerable interest for their non-toxic nature, tunable bandgap, and excellent stability. However, these quantum dots contain intrinsic sub-gap defects, which can act as donor-acceptor pairs. In this work, we synthesize AgInS2 quantum dots showing a dual emission spectrum. A narrow but weak free-exciton emission is observed near the band edge, while a broad and intense emission, associated with donor-acceptor-type defects, appears in the lower energy region. After coating the core particles with a gallium sulfide shell, the free-exciton luminescence is strongly improved, and the recombination at donor-acceptor pairs is suppressed. This demonstrates the successful elimination of defects in AgInS2/GaSx core/shell quantum dots, which is further evidenced in the absorption spectrum by the removal of a defect-related Urbach tail. In essence, we find that the donor-acceptor pair defects in these AgInS2 quantum dots are mainly located on the surface, and the excitonic character emerges upon their elimination through the growth of a gallium sulfide shell.

Keywords: Quantum dot; core shell structure; free exciton emission; donor-acceptor defect emission; carrier-trapping