Research On Preparation And Performance Of Graphene/n-Si Solar Cells

Graphene,as a representative of two-dimensional materials,takes into account both electrical conductivity and light transmittance,which makes graphene widely used in the study of new optoelectronic devices.graphene/silicon Schottky junction solar cells using graphene as transparent electrodes have the advantages of simple process and save silicon material,and are considered to be a new generation of environment friendly and high-efficiency solar cells with broad application prospects.However,the low conversion efficiency of this new solar cell limits its large-scale application.Therefore,how to improve the performance of the device has become the main research direction.In this paper,starting from the preparation of graphene films,the corresponding films were first prepared by chemical vapor deposition.,and the corresponding graphene/Si solar cells were assembled by cyclododecane-assisted transfer,and then high-performance and low-cost solar cells were prepared by introducing silicon pyramid array and nitrogen-doped carbon quantum dots as interface layer.The devices and thin films are analyzed by means of solar cell I-V test system,reflectivity,TEM,SEM,XPS and PL.The main research work is as follows:First,Graphene was prepared by RF-PECVD with copper foil as growth substrate and methane and hydrogen as reaction gas.The effects of reaction time（1min-4min）,radio frequency power（50 W-150 W）and growth temperature on the quality of graphene films were studied.The defects and crystallinity of graphene were analyzed by Raman spectrum,and the continuity of graphene was observed by SEM.By optimizing the parameters,the optimal experimental conditions were obtained as follows: reaction time 2 min,RF power 50 W,growth temperature 900 ℃.The corresponding solar cells were assembled with graphene,which showed obvious photoelectric effect.Second,the pyramid array was prepared on the silicon surface by KOH anisotropic etching,and the effect of silicon surface reflectivity on the cell performance was studied.The optimal light trapping effect was achieved when the KOH concentration was 0.05g/m L,the etching time was 30 min,and the isopropanol（IPA）content was 20%.The reflectivity decreased from 43% to 11%,which improved the solar cells’ s utilization of sunlight.Next,Gr/Si Pa solar cells were assembled on the texturing substrate.After texturing,due to the excellent anti-reflection effect,the short-circuit current density was increased by 67%,and the series resistance was reduced by 55%,so that the solar cells efficiency increased from 1.46% to 2.62%,and increased to 4.64% after nitric acid doping.Third,there is a serious interface recombination problem at the interface between graphene and silicon,which is modified and passivated by hydrothermal synthesis of nitrogen-doped carbon quantum dots（N-CQDs）.The related properties of carbon quantum dots were analyzed by TEM,PL and XPS,and the Gr/N-CQDs/n-Si Schottky junction solar cells were assembled by spin coating method,The effects of quantum dot size and spin coating times on device performance are discussed separately.The addition of N-CQDs can effectively passivate the interface,reduce the series resistance of the device,increase the filling factor from 22.3% to 31.7%,increase the efficiency from 1.46% to 4.33%,and increase the efficiency to 8.3% after nitric acid doping.