Improved ultraviolet photodetector performances using solution-processed nitrogen-doped carbon quantum dots/ZnO hybrid thin films

We fabricated the solution-processed photodetectors using the nitrogen-doped carbon quantum dots/zinc oxide (N-CQDs/ZnO) hybrid films and characterized using ultraviolet (UV) spot-light of 365 nm at 1 mW/cm2. The N-CQDs adsorbed onto the surface and/or grain boundaries of ZnO crystallites control ZnO particle size (by capping) in the N-CQDs/ZnO hybrid thin films, resulting in the improved film quality and decreased the dark current in the devices. The N-CQDs to ZnO [%(w/v)] ratio of 1.2 x 10-3 in the hybrid film UV photodetector exhibits the stable and reproducible photoresponses with the highest responsivity & external quantum efficiency (which are -3 times higher), and detectivity (-7.5 times higher) than the pristine ZnO based photodetector, attributed to the effective transfer of photogenerated electrons from N-CQDs to ZnO nanoparticles in the hybrid film. The solution-processed N-CQDs/ZnO hybrid films will be very much useful to improve the UV photodetector performances for the cost-effective commercial applications.