Wide-Bandgap Carbon Dots for Ultraviolet Photodetection: Structural Origins and Design Rules.

Tunable ultraviolet (UV) selectivity in solution-processable photodetectors remains difficult because absorption, carrier transport, and interfacial extraction are tightly coupled. Carbon dots (CDs) offer broad structural and chemical tunability, yet their structure-state-device relationships remain poorly resolved. This review introduces a core-lattice-shell framework linking local sp2 domains, atomic order and heteroatom configuration, and surface-associated states to UV absorption, transport-active states, and interfacial charge transfer. Synthesis routes are treated as reaction environments that control these coupled descriptors rather than as direct predictors of optical gaps. Device architectures are compared according to the role of CDs as UV absorbers, interface modifiers, or spectral converters in Si, metal-oxide, polymer, graphene, and carbon-nanotube systems. Across these architectures, the central design challenge is to preserve localized UV-selective states while enabling efficient charge separation and long-range transport. Progress requires structure-resolved synthesis datasets, quantitative interface verification, standardized stability testing, and function-separated architectures that decouple UV absorption from charge transport.