Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: Poster II

HL 29.68: Poster

Dienstag, 18. März 2025, 18:00–20:00, P1

Investigating Photo-Physical Properties of Ag-In-S Core and Core-shell Quantum Dots — •Johannes Kunze, Julian Mann, Sushant Ghimire, and Jochen Feldmann — Chair for Photonics and Optoelectronics, Nano-Institute Munich and Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstr. 10, 80539 Munich, Germany

Non-toxic I-III-VI quantum dots (QDs) are promising candidates for next-generation light-emitting and energy-harvesting devices. However, the optical properties in these QDs are governed by subgap defects which limit their applications. Here, we synthesize AgInS2 QDs, and study them using various steady-state and time-resolved spectroscopy. Photoluminescence spectroscopy reveals that these QDs exhibit a narrow free-exciton emission and a more dominant, broad, red-shifted emission. The observed dominance arises from defects in the QDs, which introduce donor and acceptor states within the bandgap, effectively trapping electrons and holes from the band edge. A femtosecond differential transmission spectroscopy reveals an ultrafast carrier trapping time in these QDs. Additionally, a broad absorption onset with a defect-related Urbach tail is observed. We coated AgInS2 QDs with gallium sulfide, forming core/shell QDs, which significantly enhanced the intensity of the narrow free-exciton emission, reduced defect emissions, and sharpened the absorption onset by lowering the Urbach energy. These results show that the defects in these QDs are located on their surface, and Ga-S coating effectively passivates them, improving the excitonic characteristics.

Keywords: optical properties; free-exciton emission; defect emission; core-shell; defect passivation