Triplet Exciton Convergence toward Charge-Transfer States Enables Long-Wavelength Room-Temperature Phosphorescence from Carbon Dots

Combining femtosecond transient absorption spectroscopy, single-crystal structure analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, and theoretical calculations, it was confirmed that the formation of low-energy CT states induced by matrix effects drives the migration and aggregation of intrinsic triplet excitons toward CT-related low-energy triplets, constituting the key mechanism for long-wavelength phosphorescence generation.

The broad applicability of this strategy was further validated using two different representative matrix systems. Therefore, the design strategy for long-wavelength CDs phosphorescence proposed in this study provides a new theoretical framework and design approach for the rational development of long-wavelength and even near-infrared CD-based phosphorescent materials.