Self-powered ultraviolet photodetectors offer great potential in the field of optical communication, smart security, space exploration, and others; however, achieving high sensitivity with maintaining fast response speed has remained a daunting challenge. Here, we develop a titanium dioxide-based self-powered ultraviolet photodetector with high detectivity (≈1.8 × 1010 jones) and a good photoresponsivity of 0.32 mA W-1 under pulsed illumination (λ = 365 nm, 4 mW cm-2), which demonstrate an enhancement of 114 and 2017%, respectively, due to the alternating current photovoltaic effect compared to the conventional direct current photovoltaic effect. Further, the photodetector demonstrated a high on/off ratio (≈103), an ultrafast rise/decay time of 112/63 μs, and a noise equivalent power of 5.01 × 10-11 W/Hz1/2 under self-biased conditions. Photoconductive atomic force microscopy revealed the nanoscale charge transport and offered the possibility to scale down the device size to a sub-10-nanometer (∼35 nm). Moreover, as one of the practical applications, the device was successfully utilized to interpret the digital codes. The presented results enlighten a new path to design energy-efficient ultrafast photodetectors not only for the application of optical communication but also for other advanced optoelectronic applications such as digital display, sensing, and others.
This study was supported by the National Research Foundation of Korea (NRF-2018R1D1A1B07049871 and NRF-2019R1A2C2003804) of the Ministry of Science and ICT, Republic of Korea. This work was also supported by Ajou University.
