Carbon quantum dots (CQDs) are promising luminescent nanomaterials for optoelectronic applications; however, achieving efficient solid-state emission and broadband white-light generation remains challenging due to aggregation-caused quenching and limited spectral coverage. In this work, hydrophilic solid thin-film CQDs were synthesized via a rapid microwave-assisted carbonization method. Undoped CQDs exhibited a dominant emission peak at 424 nm under excitation wavelengths ranging from 350–400 nm, displaying strong excitation-dependent photoluminescence and bright blue emission under 365 nm UV illumination. Nitrogen-and nitrogen/sulfur-co-doped CQDs demonstrated tunable emission behavior, while solid-state thin films showed suppressed aggregation effects and an enhanced quantum yield of approximately 5%. Ternary CdSe 1− x S x quantum dots were synthesized via a one-pot aqueous method, exhibiting an absorption edge near 550 nm corresponding to the first excitonic transition. Hybrid CQDs/CdSe 1− x S x nanostructures fabricated through hydrothermal integration displayed enhanced absorption intensity across 256–394 nm and broadened photoluminescence spanning ∼375–600 nm, resulting in near white-light emission under UV excitation. The broadband emission is attributed to effective interfacial exciton coupling mediated by Förster resonance energy transfer and/or photoinduced charge transfer between CQDs surface states and CdSe 1− x S x band-edge transitions. These findings demonstrate that integrating doped CQDs with alloyed CdSe 1− x S x quantum dots provides a viable strategy for tunable, broadband emission in solution-processable thin films, highlighting their potential for white light-emitting diode (WLED) applications.
Mahmoud et al. (Sat,) studied this question.