Halide-mediated surface passivation and optical modulation in Ag-In-Ga-S quantum dots: The critical role of precursor selection

초록

Ag-based I-III-VI quantum dots (QDs) are emerging as environmentally benign alternatives to heavy metal-based QDs due to their compositional flexibility, broad optical tunability, and unique emissive properties. Herein, a comparative synthesis of green-emissive quaternary Ag-In-Ga-S (AIGS) QDs with non-halide versus halide metal precursors demonstrates that halide ions play a critical role in surface passivation, enabling the suppression of defect emissions and the enhancement of band-edge emissivity. In a series of AIGS core syntheses using different Ga halides (GaX3, X=Cl, Br, I) while keeping Ag and In halides constant, the type of GaX3 is found to significantly impact their growth kinetics, composition, surface passivation, and optical properties. Compared to GaBr3 and GaCl3, GaI3 offers advantages in achieving better core composition, surface shielding, and size homogeneity, which collectively favor improved heteroepitaxial GaSx shell growth. Consequently, GaI3-based AIGS/GaSx core/ shell QDs displayed a greater photoluminescence quantum yield of 95 % relative to other halides-based counterparts (63-76 %). The findings further are corroborated by synthesizing red-emissive ternary Ag-In-S QDs with varying In halide precursors. This study underscores the importance of precursor selection in tailoring the optical properties of I-III-VI QDs for advanced optoelectronic applications.

키워드