Self-powered, transparent, flexible, and solar-blind deep-UV detector based on surface-modified TiO2 nanoparticles

Titanium oxide (TiO2) has been widely used as a low-cost, chemically stable, and biologically inert semiconductor for many applications. However, there are a limited number of studies on the application of TiO2 for deep-UV photodetection, which has potential environmental and military applications. In this study, we introduce a facile sol–gel method followed by post-modification with acetic acid (HAc) to prepare wide-bandgap anatase TiO2 (3.83 eV) for use as a solar-blind deep-UV photoabsorber. The beneficial effects of simple post-modification on the structural, optical, and electrical properties of TiO2 were comprehensively investigated. When TiO2 nanoparticles are functionalized by an appropriate number of HAc, O vacancies in TiO2 are significantly reduced while the bandgap is increased with reduced particle size. As a result, the HAc-modified TiO2-based deep-UV photodetector exhibits high specific detectivity, fast response time, and R254:R365 rejection at zero bias. Furthermore, the device displays good stability with a nearly constant photoresponse even after one month of storage and under stringent bending strain. The average visible transmittance of the device reaches as high as 80%. The results suggest that the device can be used as an efficient TiO2-based solution-processable solar-blind deep-UV photodetector, with self-powered operability, wearability, and transparency.