The effect of different rates of ultra-thin gossamer-like rGO coatings on photocatalytic performance in ZnO core-shell structures for optoelectronic applications

Abstract

In the study, core-shell-structured Al/(ZnO:rGO)/pSi/Al photo-diodes were successfully fabricated using a sol-gel spin-coating method by varying the concentration of reduced-graphene oxide (rGO) from 1 % to 9 % (wt). The ZnO:rGO composite solution was coated on a silicon (p-Si) wafer at 1000 rpm and 300 K. Both aluminum back-ohmic and front-rectifier contacts were performed on the p-Si wafer by physical-vapor-deposition (PVD). The morphological and chemical structure of the photo-diodes were determined by using field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). The current-voltage (I-V) analysis in dark and under ultraviolet (UV, 365 nm) wavelength was utilized in detail. Basic electrical parameters, including the ideality factor (n), barrier height (BH) and series-shunt resistances (R s , R sh ), were calculated using a variety of methods and compared to each other. The Card-Rhoderick method was used to extract energy-dependent profiles of interface traps (N ss ). The core-shell-structured (ZnO-7 % rGO) photo-diode exhibited the best photocatalytic performance both in dark and under various illumination intensities (50–250 mW/cm 2 ). The ZnO:rGO interlayer at the metal-semiconductor (M/S) interface leads to improvement of the photo-diode in respect of low-ideality factor/Nss/leakage-current and high-rectification and BH. • The ZnO:rGO core-shell structures were synthesized and coated successfully and homogeneously using sol-gel spin coating. • This study is pioneer due to the fact that there is no detailed study about the Al/ZnO:rGO/pSi/Al photo-diodes from ZnO:rGO interface as wrapped different rGO rates ZnO core-shell. • The rGO nanosheets were provided bridging and this may be a conductivity mechanism between ZnO spheres that increases the conductivity of the photo-diodes. • The 7 % rGO included ZnO core-shell structure has a strongly positive effect on the photo-diode performance. • The 7 % rGO included ZnO:rGO interlayer can be succesfully used instead of traditional insulator layer in the future.