Ag-to-Cu template conversion enables sharp red emission from (Cu,Ag)-In-Ga-S quantum dots with unity quantum yield

초록

Cu-based I-III-VI quantum dots (QDs) have long been constrained by defect-dominated emission, limiting narrowband, high-efficiency red output. Here we report a template-conversion strategy that transforms sharp-emissive Ag-In-Ga-S (AIGS) nanocrystals into (Cu,Ag)-In-Ga-S ((C,A)IGS) cores via post-synthetic Ag-to-Cu cation exchange, yielding excitonic red emission at 629 nm with a small Stokes shift (60 meV) and a narrow linewidth (41 nm). Sequential shell growth produces (C,A)IGS/GaSx/ZnS heterostructures with unity photoluminescence (PL) quantum yield and linewidth down to 37 nm. The ZnS outer shell suppresses oxidation-driven reconstruction of GaSx, enabling near-complete PL retention under thermal aging (85 degrees C) and markedly improved UV stability, corroborated by nearly invariant Ga 3d and S 2p X-ray photoelectron spectroscopy features after UV exposure. As color converters, these (C,A)IGS QDs outperform red InP/ZnSe/ZnS benchmarks, delivering 24%-52% higher blue absorption and 30%-44% higher blue-to-red color-conversion efficiency at identical loadings. Finally, (C,A)IGS QDs-based electroluminescent devices demonstrate pure red emission, reaching a maximum luminance of 14007 cd/m2 and an external quantum efficiency up to 13.8%.

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