Summary: | 碩士 === 國立中央大學 === 光機電工程研究所 === 103 === In this study, the intrinsic/phosphorus doping hydrogenated amorphous silicon (a-Si:H) double structure was optimized by the process conditions in which film growth of doped silicon as a back surface field (BSF) layer in a symmetric cell structure was prepared by standard radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). PF-PECVD had major advantages: (1) low operation temperature, (2) higher compactness of deposited layer, (3) good passivation properties of deposited layer, (4) good step coverage.
The process parameters effect of a-Si:H thin films such as radio-frequency power, hydrogen dilution ratio, substrate temperature, electrode distance, pressure, PH3 flow was investigated. The thin films physical and optical properties were analyzed by Four Point Sheet Resistance Meter, Hall, TEM, Ellipsometer, Photoconductance lifetime tester and Secondary Ion Mass Spectrometer. We determined the thin film quality by photo conductance lifetime tester. In addition, this double structural film will be applied to heterojunction with intrinsic thin layer (HIT) solar cells as a back surface field layer to improve the open-circuit voltage and short-circuit current of solar cells.
The results of experiments show that the excess phosphorus atoms in the films will increase the defect and degrade the electronic properties. Thus, the control of phosphorus content in the films is very important to obtain a high electronic properties. We achieved high quality of BSF on surface passivation, resulting lifetime up to 1.5ms and concentrations > 1019 in 4cm2 HIT solar cell.
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