Enhancement of electrical properties by CuS–PVP nanocomposite on the ZnO/polymer heterojunction

A nanocomposite matrix of covellite–polyvinylpyrrolidone (CuS–PVP) was synthesized through a solution processing method and applied via spin coating onto hydrothermally grown zinc oxide (ZnO) nanorods. Characterization techniques, including X-ray powder diffraction and scanning electron microscopy, confirmed the successful decoration of chain-like CuS–PVP polymer composites onto hexagonal ZnO nanorods. The UV-vis spectroscopy revealed an absorption peak at 372 nm, indicating excitonic absorption of ZnO, and a reduction in the band gap from 3.11 to 2.59 eV upon CuS–PVP polymer decoration, enhancing light harvesting efficiency. Photoluminescence spectra demonstrated the lowest charge carrier recombination rate in the ZnO/CuS–PVP sample, promoting efficient charge separation and transportation, supported by Fourier-transform infrared analysis indicating chemical bonding. Subsequently, the impact of CuS–PVP as an insertion layer in the ZnO/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) inorganic–organic heterojunction was investigated. Favorable band alignment between ZnO, CuS–PVP, and PEDOT:PSS improved conduction, increasing current from 0.3394 to 1.14 mA for D2 (poly-ethyleneterephthalate/Indium tin oxide/ZnO/PEDOT:PSS/Al) and D1 (poly-ethyleneterephthalate/Indium tin oxide/ZnO/CuS–PVP/PEDOT:PSS/Al) at a +2 V bias. Transient photo-responses (J–t) at 0 V bias revealed decreased rise and fall times from 0.382 and 1.154 s to 0.301 and 0.229 s for D2 and D1 devices, respectively. This novel approach provides control over charge carrier transport characteristics at the interface, potentially benefiting self-powered photo-detection in optoelectronic devices.