Ginger extract (GE) was employed for the reduction of graphene oxide (GO) by refluxing in an aqueous medium with different reduction times. The reduced GO was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) to investigate structural, chemical bonding and functional groups, respectively. The XRD results reveal that the maximum reduction GO was observed at 12 h. The scanning electron microscopy (SEM) images showed the formation of a thin sheet-like structure for ginger reduced graphene oxide (GRG12). The electrochemical properties of GRG samples were further evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The GRG12 showed the highest specific capacitance value of 99.61 F g$^{-1}$ at a scan rate of 5 mV s$^{-1}$ with cycling stability of 98% after 1000 cycles. This study demonstrates the potential of GE for the reduction of GO and efficiency of the reduced product for application in supercapacitors.

Silicon nanowire (SiNW) hybrid solar cell has been fabricated using PEDOT:PSS and rGO-PEDOT:PSS as the organic hole transport layer. The electrical characterization of the as-fabricated solar cell was done by both dark and photo $J–V$ characteristic curves. Vertically aligned arrays of SiNWs have been synthesized by following the electroless metal-assisted chemical etching method, as confirmed by both the scanning electron microscopy and atomic force microscopy images. The structural properties of SiNWs, PEDOT:PSS and rGO-PEDOT:PSS were characterized with thehelp of X-ray diffraction and Raman characterization techniques. The bandgap of PEDOT:PSS comes out to be 1.77 eV asobtained from the UV–visible and photoluminescence spectra. In addition, the bandgap of PEDOT:PSS was 1.76 eV and for reduced graphene oxide (rGO) it was 0.04 eV, as obtained from the cyclic voltammetry curve. rGO-PEDOT:PSS heterojunction showed excellent $J–V$ characteristic property in the dark and under the illumination of 1 sun. Hence the incorporation of rGO in PEDOT:PSS can improve the photovoltaic properties by increasing the conductivity of the hole transport layer, making a good interface between organic–inorganic heterojunction as well as by reducing the recombination of electron–hole pairs.