Variation in the Optical Properties of Carbon Dots Fabricated by aGreen and Facile Strategy for Solar-Blind UV Detection br

Despite the strong light absorption and highefficiency of multiple carrier generation and collection of carbondots (CDs), little attention has been paid to thefield ofphotodetection. Herein, CDs are synthesized through a greenand facile strategy, which only uses graphite rods and distilledwater. It is found that the oxygen content and the optical propertiesof CDs could be modulated by the voltage applied between the twographite rods. A series of tests reveal that the excitation-independent blue photoluminescence (PL) emission of as-preparedCDs is related to the topological defects. And the oxygen-containing groups would bring new energy levels between the bandgaps of CDs, which enhanced the excitation-dependent yellow-green PL emission and the absorption from the near-ultraviolet(UV) to the visible range. The CDs with fewer oxygen-containing groups show strong UV absorption and short cutoffwavelength,and they are utilized to fabricate solar-blind UV photodetectors. Tested under 254 nm UV illumination, the detectors exhibit a highphotoresponsivity (1.14 mA/W) and highly characteristic wavelength-dependent response (R254/R365= 115). This study provides adeeper understanding of the relationships between optical properties and the structure/composition of CDs. More importantly, thesolution processability of CDs paves the way for future high-performance, low-cost solar-blind photodetectors.