CuO/Cu core/shell nanostructured photoconductive devices by hot water treatment and high pressure sputtering techniques

Abstract

This work demonstrates the fabrication of simple photoconductive devices based on CuO/Cu core/shell nanostructured heterojunction that performs notable photocurrent response. Copper oxide (CuO) nanoleaf structures (NLs) have been successfully grown on ITO-coated glass substrate via a simple hot water treatment (HWT) method. A conformal Cu shell was fabricated by high pressure sputtered (HIPS) deposition technique on the CuO nanoleaves to produce NLs-core/metal shell photoconductive devices. For comparison, CuO thin film (TF) was prepared by the thermal oxidation method to manufacture the conventional planar thin film devices. Results showed that the HWT method resulted in the formation of dense 3D CuO nanoleaves on ITO/glass substrate with a high surface area. CuO NLs showed higher optical absorption than CuO TF in the ultraviolet and visible spectrum. Further, the optical band gaps of CuO NLs and TF samples have been estimated from Touc’s plot to be 1.45 ± 0.10 eV and 1.63 ± 0.20 eV, respectively. Current density–voltage measurements’ result revealed that core/shell devices have superior photocurrent response compared to TF devices. The average photocurrent density at zero-bias for the NLs devices was 23.5 ± 2.0 μA cm−2 and for TF devices was 6.7 ± 1.0 μA cm−2. Besides, NLs core/shell photoconductive devices exhibit a remarkable increase in photocurrent response values with increasing bias voltage compared to the increased values in TF devices. The results demonstrate that the devices based on HWT-NLs-core/HIPS-shell design showed a significant enhancement on the photoconductivity response compared with the conventional TF design. The performance enhancement can be attributed to improving light trapping, photocarriers generation-recombination times and carrier collection by introducing an alternative radial interface in core/shell design. Also, HWT CuO NLs geometry feature with the high surface area has worked to enhance light absorption that enables the design of high efficiency, functional and commercial photoconductive detectors.