Working gas pressure during sputter deposition can significantly affect the conformality of a thin film when it is grown on a nanostructured surface. In this study, we fabricated core-shell nanostructured photodetectors, where n-type In2S3 nanorod arrays (core) were coated with p-type CuInS2 (CIS) films (shell) at relatively low and high Ar gas pressures. In2S3 nanorods were prepared by glancing angle deposition (GLAD) technique using a thermal evaporator unit. CIS films were deposited by RF sputtering at Ar pressures of 2.7x10-2 mbar (high pressure sputtering, HIPS) and 7.3x10-3 mbar (low pressure sputtering, LPS). The morphological characterization was carried out by means of SEM. The photocurrent measurement was conducted under 1.5 AM Sun under no bias. Nanostructured photodetectors of HIPS-CIS/GLAD-In2S3 (i.e. HIPS-GLAD) were shown to demonstrate enhanced photoresponse with a photocurrent value of 98 μA, which is about ∼230% higher than that of LPS-GLAD devices. The enhancement originates from the improved core-shell structure achieved by more conformal coating of the CIS shell. In addition, the results were compared to their counterpart thin-film devices incorporating an In2S3 film coated either with HIPS or LPS CIS layer. Nanorod devices with high and low pressure CIS films showed photocurrent values ∼20 times and ∼ 19 times higher compared to those of high and low pressure film devices, respectively. This finding can be explained by the higher light absorption property of nanorods, and the reduced inter-electrode distance as a result of core-shell structure, which allows the effective capture of the photo-generated carriers. Therefore, the results of this work can pave way to the development of high photoresponse core-shell semiconductor devices fabricated by physical vapor deposition techniques.

We report on the photovoltaic characteristics of molecular beam epitaxy-grown PiN InGaN nanorod solar cells. The glancing angle deposition process was adapted to grow continuous transparent metal layers on discontinuous nanorods. A short-circuit current density of 4.6 mA/cm 2 and an open-circuit voltage of 0.22 V with a power conversion efficiency of 0.5% under 1 sun, air-mass 1.5, illumination were observed. The excellent lightgenerated current in the InGaN nanorod solar cells is considered to stem from the improved crystal quality owing to the strain-free nature as well as the enhanced light concentration effects in the nanorod configuration.

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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.