## 1 Introduction  
Crystalline silicon nanowires (SiNWs) usually exhibit a highly efficient light absorption and an antireflection of the incident light greater than that of a flat surface silicon material of the same size [1]. Geometrical scattering and antenna effect of the SiNWs are the main reasons for high light-harvesting performance [2, 3], where the NW density and diameter determine the absorbed wavelength, which is called the resonance wavelength [4]. One more advantage of the SiNW solar cell is the simplicity of the fabrication process with a large-area scalable structure, as introduced by [PERSON] and [PERSON] [5]. This process produced a high open-circuit voltage value, \(V_{cc}\), and high fill factor, \(FF\), which lead to producing higher overall efficiency, \(\mu\), of the solar cell for high values of short-circuit current density, \(J_{sc}\). However, we still need to increase the value of the \(J_{sc}\), which can be obtained by using an absorber layer, such as graphene, \(C\)[6]. For its good electric properties, as a thin and highly transparent material, graphene has been greatly used in recent research [7]. Graphene on a silicon surface forms a Schottky junction solar cell with a very low efficiency, which can be improved by engineering the interface with a passivation layer to increase the graphene work function [8]. On the other hand, plasmonic nanoparticles have high absorption properties which depend on the surrounding medium and the size, shape, and material of the nanoparticles [9]. In this work, we used a graphene layer and plasmonic NPs distributed on the top of a silicon surface to enhance the power conversion efficiency (PCE) of the SiNW solar cell [10, 11, 12]. Large-area SiNWs with radial PN junctions have been produced using a simple fabrication method by [PERSON] and [PERSON] [5]. The fabricated solar cell was based on a room-temperature aqueous etching method and low-temperature thin film deposition with a rapid thermal annealing crystallization process. The given method increased the PCE to be 5.3% with \(V_{\infty}=0.56\) V, \(FF=0.607\), and \(J_{sc}=17.32\) mA/cm\({}^{2}\). A SiNW solar cell grown on a silicon base and covered with an on-site graphene layer for Schottky junction was introduced by [PERSON] et al. [6]. The graphene layer increased the carrier collection and enhanced the solar cell efficiency to be 3.83%. The obtained open-circuit voltage is 0.47 V, the fill factor is 0.59, and the short-circuit current density is 13.7 mA/cm\({}^{2}\). [PERSON] and [PERSON] fabricated a SiNW nanostructure on a silicon base photovoltaic, which achieved light absorption [1]. In addition, a 3D radial junction solar cell has been developed in order to overcome light-induced degradation. The experimental results illustrated that the maximum obtained open-circuit voltage from the solar cell is 0.82 V and the \(FF\) is 0.73, while the short-circuit current density is 15.2 mA/cm\({}^{2}\), which leads to a power conversion efficiency of 9.3%. A large-scale silicon solar microcell fabricated from bulk wafers using transferring printing technique was presented by [PERSON] et al. [13]. The produced device has many features such as mechanical flexibility, transparency, and ultrathin microconcentrator designs. Theoretical and experimental electrical, mechanical, and optical characteristics of several types of modules were illustrated in this work. The measured \(V_{\infty}\) is 0.51, \(FF\) is 0.61, \(J_{sc}\) is 33.6 mA/cm\({}^{2}\), and PCE is 11.6%. [PERSON] et al. showed the analytical model of the recombination mechanisms of a silicon solar cell with low bandgap-voltage offset [14]. The work showed the effect of changing excess carrier density on the effective lifetime of the carriers. The untextured structure, with 50 \(\upmu\)m thickness, produced 0.764 V as an open-circuit voltage, a fill factor of 0.86, and a short-circuit current density of 38.8 mA/cm\({}^{2}\).