Highly Sensitive and Self Powered Ultraviolet Photo Detector based on ZnO Nanorods Coated with TiO$_2$

TL;DR

This paper reports the development of a highly sensitive, self-powered UV photodetector using ZnO nanorods coated with TiO$_2$, demonstrating enhanced photocurrent, responsivity, and detectivity due to heterostructure effects.

Contribution

The study introduces a novel ZnO@TiO$_2$ nanorod-based UV photodetector with significantly improved performance and provides theoretical insights into the heterostructure's electronic and optical properties.

Findings

Photocurrent increased from 6 μA to 17 μA in UV light in the 'ON' state.

Dark current increased from 0.08 μA to 0.6 μA in the 'OFF' state.

Photocurrent enhancement of 250 μA compared to 35 μA for bare ZnO NRs at 10 V.

Abstract

Nanorods (NRs) of crystalline ZnO coated with thin layers of TiO$_2$(ZnO@TiO$_2$) were fabricated with the help of the spin coating technique followed by the hydrothermal method. Scanning electron microscopy (SEM) and X-ray diffraction analysis confirms the morphology and structural stability of as-prepared NRs. The optical band gaps of the NRs were estimated, and a clear blue shift toward the UV region has been detected. When UV light falls on as-prepared device (i.e., in the "ON" state), a significant increase in photocurrent (I$_{UV}$) at zero voltage supply was observed from 6 $\mu$A to 17 $\mu$A while in the "OFF" state, the dark current (I$_{dark}$), increases from 0.08 $\mu$A to 0.6 $\mu$A with ZnO@TiO$_2$ NRs as compared to bare ZnO NRs respectively. Responsivity and detectivity of TiO$_2$ coated ZnO NRs based device found maximum in UV region unlike bare ZnO NRs. Enhanced photocurrent achieved by the growth of TiO$_2$ layers on ZnO NRs is 250 $\mu$A as compared to bare ZnO NRs for which it is 35 $\mu$A at 10 V voltage supply under the ultraviolet irradiation (illumination intensity of 1 mW/cm$^2$). Furthermore, theoretical calculations have been performed using the first-principles density-functional theory to understand the effects of heterostructure NRs on the electronic and optical properties of TiO$_2$ coated ZnO.