Efficiency enhancement of TiO2 self-powered UV photodetectors using a transparent Ag nanowire electrode

A novel efficient way to realize high performance TiO2 self-powered UV photodetectors (PDs) with enhanced responsivity is proposed in this work. By constructing asymmetric electrodes consisting of a commercial mixed silver paste and two different forms of Ag nanostructures (nanofilms and nanowires) on the active layer of TiO2, respectively. Both PD devices exhibited attractive photovoltaic characteristics in a self-powered mode (at 0 V bias). Interestingly, the responsivity of the TiO2 UV PDs is found to be enhanced by 9 times at the wavelength of 350 nm without any power supply when the configuration of the Ag nanostructure electrode was changed from nanofilms to transparent nanowires. The enhanced photoelectric conversion efficiency is mainly attributed to a modified Schottky barrier through reducing hole traps and a higher light absorptivity through using a transparent electrode according to the experimental results and physical models based on the energy band theory. In addition, TiO2 UV PDs with a Ag nanowire electrode also exhibited excellent photoelectric properties in terms of a high linear dynamic range of 103.7 dB, a fast response speed (rise time of 2 ms and fall time of 41 ms), and excellent stability. The design solutions proposed here may provide additional opportunities for further development of Schottky junction-based self-powered UV PDs with high efficiencies.