Research Of N-type Interdigitated Back Contact Silicon Photovoltaic Cell By Aluminum Diffusion

The interdigitated back contact photovoltaic cell is a novel cell structure.The front surface of the cell has no grid lines,which can reduce the optical loss and improve the efficiency of the cell.The ordinary N-type cells are produced by high-temperature boron diffusion.As a substitute of boron diffusion,aluminum diffusion cells can avoid the damage of silicon wafer and the production of B-O compound pair in high temperature process,and the fabrication process is more economical and convenient.Therefore,the N-type interdigitated back contact silicon photovoltaic cell by aluminum diffusion is considered to be the most effective way to improve cell efficiency while to reduce manufacturing costs.By introducing the physical basis of crystalline silicon photovoltaic cells and related theories,this thesis establishes the structure model of N-type interdigitated back contact silicon photovoltaic cell using simulation software PC1D.Based on the requirements for the preparation of high-efficiency interdigitated back contact N-type silicon photovoltaic cells,the cell parameters are set to simulate numerically the cell characteristics.The influences of the front surface structure parameters,substrate parameters and back surface structure parameters on the main performance parameters of the cell are systematically studied and analyzed.The highest efficiency expected to be achieved and the optimal process conditions obtained theoretically are calculated.The electrode preparation technology that simultaneously meet low series resistance,low interface state and low recombination rate is researched to solve the leakage problem of Al-P⁺emitters formed by direct sintering in order to maximize cell efficiency.The main work completed in this thesis is as follows:?1?Using crystalline silicon photovoltaic cells as the research basis,this thesis studies the working principle,characterization and the structure and characteristics of high-efficiency crystalline silicon photovoltaic cells,so as to design an aluminum diffused N-type silicon photovoltaic cell with interdigitated back contact structure.?2?The structure of the interdigitated back-contact photovoltaic cell is designed.The PN junction and metal electrodes of the cell are all arranged on the back of the cell,and the positive and negative electrodes are arranged in a cross shape with fingers.The front surface adopts the"pyramid"suede structure.The light phosphorus and concentrated phosphorus are diffused in different areas.The localized and small area aluminum diffusion P⁺region is on the back surface.The double-sided passivation of SiO₂/SiN_x and Al₂O₃/SiN_x are adopted.According to the device structure,the PC1D physical model is built and simulation parameters are set.The fabrication process of interdigitated back contact photovoltaic cells is researched.?3?Using PC1D to numerically simulate the interdigitated back contact photovoltaic cell.This thesis analyzes respectively the impact on the output characteristics of photovoltaic cells of the surface doping concentration of the front surface field and the back surface field,the front surface recombination rate,the substrate thickness,the volume resistivity and the volume life,P⁺emitter doping concentration and depth.According to the simulation results,the interdigitated back contact photovoltaic cell is optimized.The optimized cells have good output characteristics,and the conversion efficiency is as high as 23.54%under AM1.5conditions.?4?This thesis analyzes the Auger recombination and SRH recombination of the Al-P⁺emitter,and studies the modification and passivation of the Al-P⁺emitter.Through theoretical simulation,the interdigitated electrode with low recombination state and no leakage phenomenon is designed,thereby improving the conversion efficiency of the cell.