Research And Theoretical Simulation Of Silicon Heterojunction Solar Cells

Due to high conversion efficiency,simple process,low temperature coefficient,and the advantages of the low temperature process,HIT solar cells had been widely attentioned.Different to traditional crystalline silicon diffusion process,HIT solar cells deposited the intrinsic amorphous silicon thin film on both sides of the silicon wafer surface to achieve good passivation effect,and then the doped p and n amorphous silicon layer were deposited on the intrinsic layers to form the heterojunction cell structure.In the case of illumination,the generated holes are transported towards the amorphous p layer,and the electrons are transported toward the amorphous n layer,thereby bringing carrier separation.In this paper,the effects of silicon cleaning and intrinsic layer passivation on the performance of the cells were studied,and the simulation of the new HIT solar cell was done by simulation software.This paper is divided into three parts,and the first part is the texture of silicon wafers and characterization of morphology and light reflection properties.In the cleaning process,ammonia and hydrogen peroxide were used for initial cleaning to remove some of the contaminants,followed by 20%concentration of potassium hydroxide solution to remove the destructive layer,then by the use of potassium hydroxide on the monocrystalline silicon to make heterodromous corrosion and different concentrations of heterodromous factors using additive solution for monocrystalline silicon to form the the pyramid structure on the surface to reduce reflection and increase the absorption of light.By changing the temperature of the texture fluid,the time of texture process,and the proportions of the components in the additive,we can control the size of the pyramid to match the deposition of the intrinsic amorphous silicon thin film to obtain a higher minority lifetime which brings good passivation effect,higher open circuit voltage and conversion efficiency.The second part is to optimize the intrinsic amorphous silicon thin film on the textured silicon surface,so that we can achieve good passivation effect and improve the efficiency of the solar cells.The intrinsic a-Si:H thin film has a very good effect to passivate the surface defects of crystalline silicon,which can greatly reduce the surface recombination of the crystalline silicon.After depositing the intrinsic layer,the recombination rate can be reduced to 3cm/s,ensuring that the soalr cells can get high open circuit voltage.Therefore,the quality of the intrinsic amorphous silicon thin film has a great influence on the electrical performance of the HIT solar cells.We have prepared high quality intrinsic amorphous silicon thin films by adjusting different deposition temperatures and different intrinsic layer preparation conditions.By optimizing the deposition temperature,deposition power,deposition pressure and hydrogen dilution of amorphous silicon thin films,we achieve a good passivation layer,the minority carrier lifetime can reach 3 ms.Subsequently,an efficient HIT solar cell was prepared by optimizing the doping layers and ITO process.When the deposition temperature is 225 ℃,the deposition power is 10 W,the pressure is 2 T,the minority carrier lifetime of passivated silicon wafers is up to 3 ms,and the short circuit current of the solar cells is 40.5 mA/cm2 and the efficiency is 21.68%.The third part is to simulate the new heterojunction solar cells by simulation software AFORS-HET,We used AFORS-HET to design a new double emitter HIT solar cell.By studying the influence of the emitter thickness,doping concentration and the parameters of the TCO on the solar cell performance of the double emitter cells,We find that when the light doping layer thickness is 5 nm,the light doping concentration is 7.5×1019 cm-3,the heavy doping layer thickness is 5 nm,the doping concentration is 2×1020 cm-3,the HIT solar cell simulation conversion efficiency is obtained up to 25.6%.