An adjustable multi-color detector based on regulating TiO₂ surface adsorption and multi-junction synergy

A TiO₂-based multi-color photodetector with controlled photoelectric response to ultraviolet (UV) and visible light is developed by using band regulation technologies such as multi-junction synergy and surface adsorption. This photodetector is manufactured via a continuous process including magnetron sputtering, hydrothermal growth, hydrogen annealing, spin coating and thermal evaporation assembly to form a structure of N-doped TiO₂/hydrogenated-TiO₂/p-Si heterojunction. These synergistic effects form electronic potential wells in the device to control the electrical transport and spectral response of photo-generated carriers. In the air, the device exhibits a controllable photodetection ability that responds to visible light at positive voltages and UV light at negative voltages. But in vacuum (< 0.1 Pa), the photodetection ability of the device at negative voltages is greatly reduced due to the lack of barrier effect caused by surface adsorption. On the contrary, the photodetection ability at positive voltage (e.g., 4 V) has been greatly improved, and the quantum efficiency reaches 206.6% under the 480 nm wavelength light. The device has a controllable ability to detect UV and visible light depending on the environments, which is very useful in the fields of environmental detection, chemical sensing and multi-color communication, etc.