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Role of the Electron Dark Current and Early Effect in the Degradation of the Open Circuit Voltage and S-Shape Distortion in a-Si:H(p)/c-Si Heterojunction Solar Cells with Schottky Contact
M.Y. Ghannam, Y.M. Abdulraheem, I. Gordon, J. Poortmans
Heterojunction, a-Si:H, Silicon Solar Cell
Silicon Materials and Cells
Subtopic: Characterisation & Simulation of Si Cells
Event: 8th World Conference on Photovoltaic Energy Conversion
Session: 1BO.5.5
74 - 78
ISBN: 3-936338-86-8
Paper DOI: 10.4229/WCPEC-82022-1BO.5.5
0,00 EUR
Document(s): paper


A bipolar equivalent circuit model is developed for silicon hetero-junction silicon solar cells (HJT) with a Schottky contact between the p-type amorphous silicon and the transparent conducting oxide (TCO). The Schottky barrier is treated as a bipolar collector junction through which holes are transported by thermionic emission, while electrons reaching the barrier are swiftly collected. The electron current is shown to exhibit an Early effect especially in cells with low a-Si:H(p) doping level. The results of the equivalent circuit analysis in the dark and under illumination perfectly match the J-V characteristics resulting from AFORS-HET device simulations of cells with low and with high doping levels in aSi:H(p). The model provides a clear interpretation for the role of the Schottky diode in the degradation of the cell open circuit voltage and in the S-shape distortion of the J-V characteristics under illumination.