The Simulation Of A-Si/μc-Si Tandem Solar Cells And Research In μc-SiOx Thin Film

A-Si thin film solar cells has excellent photoelectric properties like simple preparation process, low production cost, manufacturing in large area. However, a-Si thin film solar cells is faced with two big problems that is the low conversion efficiency, and the poor stability caused by S-W effect.Replacing the original window layer by wide band gap materials such as a-SiOx,a-SiC,μc-SiOx and the use of a-Si/μc-Si tandem structure have become a more effective way to improve the conversion efficiency and stability of cells.In this paper, we studied the influence of each layer parameters to the the performance of a-Si solar cells by using wxAMPS simulation software. For the a-Si/μc-Si tandem solar cells, the key factors that affect the performance of cells was investigated from the top and bottom cells thickness matching as well as tunneling recombination junction. At the last, we prepared different μc-SiOx thin films under the condition of different process parameters, and explored the influence of process parameters to the photoelectric properties (transmittance, light dark conductivity)of thin films.(1)The doping concentration in window layer and the defect density in the intrinsic absorption layer was the key factor that influence the performance of cells.The performance of cells will deteriorate rapidly when the doping concentration in window layer is lower than 1019cm-3, or intrinsic absorption layer defect density is higher than 1017 cm-3eV-1. The performance of cells will increases with increasing in the band gap of window layer and thickness of intrinsic absorption layer at first then decreases, the optimal value of window layer and thickness of intrinsic absorption layeris 2.2 eV and 300 nm.(2) The top and bottom cells thickness matching as well as the middle defect state density and the doping concentration of tunneling recombination junction has a great influence in the performance of a-Si:H/μc-Si:H tandem solar cells. The best solar cell performace would be achieved when the intrinsic layer thickness from top to bottom is set to be 200 nm and 2000 nm as the same time the middle defect state density and the doping concentration is set to be 1017cm-3 eV-1 and 5×1019 cm-3.(3) Incorporation of oxygen in microcrystalline silicon can effectively improve the transmittance of thin film, but at the same time, the mixed oxygen can lead to sharply declining in light and dark conductivity of thin film, oxygen adding ratio (the ratio of CO2/SiH4) should not be higher than 0.1. Transmittance of thin films will decrease with the increase of rf power, the light and dark conductivity of film will with increase with the increase of rf power at first and then decrease, the optimal value of rf power is 100 w. Growth temperature has a little effect on the transmittance of thin films, but is the main influence of light dark conductivity of thin film, the higher temperature will get the better light dark conductivity.