Carbon Dots for Electroluminescence: Bridging Molecular Fluorophores and Quantum Emitters.

Carbon dots (CDs) are an emerging class of carbon-based luminescent nanomaterials composed of localized sp2-conjugated domains and edge/surface functional groups. Unlike inorganic quantum dots, CDs are constructed from earth-abundant, low-toxicity elements and can be chemically programmed through precursor design, heteroatom incorporation, edge-state regulation, and topology engineering. At the same time, unlike molecular fluorophores, CDs are nanoscale condensed-state emitters whose optical properties are governed by quantum confinement, chemical composition, aggregation, interdomain coupling, and solid-state organization. CDs therefore occupy a unique position between molecular emitters and semiconductor quantum dots. This hybrid identity becomes particularly important in light-emitting diodes (LEDs), where electroluminescence arises not from intrinsic photophysical properties alone but from the coupled interplay of charge injection, carrier transport, exciton confinement. As a result, electroluminescent performance cannot be directly inferred from solution-phase photoluminescence. This distinction is especially critical for CDs, whose emissive states are highly sensitive to condensed-state packing, interfacial interactions, and device architecture, often leading to a disparity between photoluminescence efficiency and electroluminescent performance. Within this context, we show that CDs offer unique opportunities for electroluminescent applications while also presenting fundamental challenges. Their emission is highly tunable through structural and chemical design, enabling broad spectral control across the visible region. Their carbon-based composition provides a heavy-metal-free alternative to Cd- and Pb-based emitters, and their solution processability supports scalable thin-film fabrication. However, conventional CDs suffer from broad emission bandwidths, structural heterogeneity, aggregation-induced quenching, and fluorescence-dominated exciton utilization, which limit efficiency and color purity. We identify that recent progress lies not only in achieving electroluminescence, but in transforming CDs into increasingly programmable emissive systems. In this Account, we present the evolution of CD-based electroluminescent materials from the perspective of coupled structure-photophysics-device relationships. We first establish the device framework of CD-LEDs, including multilayer architectures, energy-level alignment, and the role of the emissive layer in charge recombination and exciton relaxation. We then discuss synthetic strategies that advance CD emitters from empirically carbonized products toward increasingly structure-defined systems. On this basis, we highlight four key directions: multicolor electroluminescence via hierarchical emissive-state regulation, narrowband emission through molecular programming, efficient solid-state emission, and triplet-exciton management. Together, we demonstrate that these advances establish CDs as a class of programmable electroluminescent materials bridging molecular photophysics and quantum optoelectronics.