Selenium-sensitized TiO2 p-n heterojunction thin films with high resistance to oxidation and moisture for self-driven visible-light photodetection

Semiconductor-sensitized TiO 2 thin films have been widely applied in optoelectronic devices. Here we prepared narrow bandgap (∼1.77 eV) selenium (Se)-sensitized TiO 2 thin films by spin-coating of Se inks onto a TiO 2 mesoporous layer, which forms a p-Se/n-TiO 2 heterojunction interface and holds promise for self-driven visible-light detection and sensing. Under irradiation by simulated sunlight and monochromatic visible-light, the resultant films exhibit large on-off switch ratio, fast response speed, and high spectral responsivity and detectivity at zero bias. Meantime, the p-Se/n-TiO 2 films show notable photoresponse stability and can maintain 92% and 64% of photocurrent of the pristine device after 2-month air storage and 72 h water soaking, respectively. Such good oxygen and moisture resistance of Se/TiO 2 thin films would be promising as applied in environmentally-stable heterojunction optoelectronic devices.