High performance flexible copper indium gallium selenide core–shell nanorod array photodetectors

Abstract

In this study, the authors fabricated high performance core–shell nanostructured flexible photodetectors on a polyimide substrate of Kapton. For this purpose, p-type copper indium gallium selenide (CIGS) nanorod arrays (core) were coated with aluminum doped zinc oxide (AZO) films (shell) at relatively high Ar gas pressures. CIGS nanorods were prepared by glancing angle deposition (GLAD) technique using radio frequency (RF) magnetron sputtering unit at room temperature. AZO films were deposited by RF sputtering at Ar pressures of 1.0×10−2 mbar (high pressure sputtering) for the shell and at 3.0×10−3 mbar (low pressure sputtering) to create a top contact. As a comparison, the authors also fabricated conventional planar thin film devices incorporating CIGS film of similar material loading to that of CIGS nanorods. The morphological characterization was carried out by field-emission scanning electron microscope. The photocurrent measurement was conducted under 1.5 AM sun at zero electrical biasing, where CIGS devices were observed to absorb in the ultraviolet-visible-near infrared spectrum. GLAD core–shell nanorod photodetectors were shown to demonstrate enhanced photoresponse with an average photocurrent density values of 4.4, 3.2, 2.5, 3.0, and 2.5 μA/cm2 for bending angles of 0°, 20°, 40°, 60°, and 80°, respectively. These results are significantly higher than the photocurrent of most of the flexible photodetectors reported in the literature. Moreover, our nanorod devices recovered their photoresponse after several bending experiments that indicate their enhanced mechanical durability. On the other hand, thin film devices did not show any notable photoresponse. Improved photocurrent of CIGS nanorod devices is believed to be due to their enhanced light trapping property and the reduced interelectrode distance because of the core–shell structure, which allows the efficient capture of the photo-generated carriers. In addition, enhanced mechanical durability is achieved by the GLAD nanorod microstructure on a flexible substrate. This approach can open a new strategy to boost the performance of flexible photodetectors and wearable electronics.