Research On Back-point Contact Thin Film Silicon Photovoltaic Cells

In the back-contact thin-film silicon solar cells,the positive and negative electrodes both are put on the back which solves the problem that the positive electrode blocks the incident light leading to light loss.However,the back electrode increases the back surface metal coverage and the series resistance of the cell,and also needs complex doping process that increase the process cost.To reduce the cost,we propose a new architecture for thin film solar cells in which point metal contacts and one doping layer are used,and It can reduce the metal-semiconductor contact area.In addition,the back-point contact type cell requires only one high-temperature doping which leads to the cost similar to that of classic solar cells.It is of great significance to the development of such solar cells.the photovoltaic industry.The main research contents of this paper are as follows:First of all,the optical and electrical losses that affect the performance of the solar cells were analyzed,and an improved method was proposed.For optical loss,a full back structure can be adopted to solve the front electrode shielding loss.On the front surface,we can deposit the anti-reflection film on the light-receiving surface,or prepare a light trapping structure to reduce the reflection loss.For electrical loss,a passivation film can be deposited on the light-receiving surface of the cell to reduce the surface combination loss.Then,the semiconductor simulation software TCAD was used to establish the physical model of back point contact thin-film silicon solar cell.The influence of the silicon absorber layer thickness on the performance of the solar cell was analyzed and the advantages of thin-film silicon cell were illustrated.The effects of P and N electrode contact width,P contact depth,and N-doping time on the performance of back-contact thin-film silicon solar cells were simulated.The optimal cell structure parameters and process parameters were obtained.based on the optimization of the cell parameters,the preparation process of back-point contact thin film silicon solar cells was studied.The principle and specific process conditions of high-temperature diffusion,thermal oxidation,photolithography,wet etching,junction depth measurement,electron beam evaporation,dry etching,and annealing were introduced,respectively.some back-point contact solar cells were is prepared.Finally,the performance of the back-contact cells before and after annealing was studied.The conversion efficiency of the thick silicon cell after annealing was 10.48%.Subsequently,dry etching method was used to reduce the thickness of silicon solar cells and the Si₃N₄ anti-reflection film was introduced.the reduced thin-film silicon cell has an efficiency of 6.34%.