Oxygen Plasma Surface Activation of Electron-Depleted ZnO Nanoparticle Films for Performance-Enhanced Ultraviolet Photodetectors

Zinc oxide (ZnO) nanoparticles (NPs) with uniform particle radius comparable to the desired Debye length provide a low-cost and a scalable scheme to achieve optimized electron depletion effect, which is the key to high performance ultraviolet (UV) photodetection. Here, a simple and improved sol–gel method for in situ synthesis of highly crystalline constituent ZnO-NP mesoporous thin films is reported. In combination with optimal oxygen plasma treatment to activate the ZnO-NP surface, the UV-detection performance is enhanced remarkably with a reduced dark current by one order of magnitude and an increased UV detectivity by over 300%. Moreover, such UV photodetectors exhibit extraordinary performance with high responsivity of up to 0.8 A W−1V−1 at 340 nm UV power of 0.003 mW cm−2, detectivity of 1.4 × 1011 Jones, and rise/decay time of 3.4 s/5.0 s. These results illustrate that the sol–gel ZnO-NP films provide a promising template for high-performance UV detectors to take full advantages of the electron depletion effect.