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Optimization of Silicon Heterojunction Cells: A Recipe for More Than 26% Efficiency
M.Y. Ghannam
Thin Silicon, Valence Band Offset, Silicon Heterojuction (SHJ) Solar Cells, Cell Efficiency, Work Function
Silicon Cells
Subtopic: Heterojunction Solar Cells
Event: 35th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2AV.3.25
681 - 685
ISBN: 3-936338-50-7
Paper DOI: 10.4229/35thEUPVSEC20182018-2AV.3.25
0,00 EUR
Document(s): paper, poster


Optimum conditions for high efficiency silicon heterojunction solar cells are investigated. It is shown that a large difference between the work functions of the p-type doped amorphous silicon layer (a-Si:H) and that of the n-type crystalline silicon substrate is required but subject to constraints imposed by the valence band offset and by doping concentrations. The optimum cell design when such constraints are taken into consideration should use a-Si:H with a band-gap in the 1.6-1.63 eV range with an electron affinity in the range 3.85-3.9 eV. The p-type doping concentration in a-Si:H should be around 1020 cm-3 with a maximum allowed peak dangling bond density half this concentration, and a substrate doping concentration in the 8x1016 to 1017 cm-3 range with a carrier lifetime in the ms range. With such a design, the predicted efficiency ranges from 25.6-26% for the full wafer thickness SHJ cell, and with effective light trapping reaches 26.1-26.4% for the thin 100 m SHJ cell and 26.3-26.9% for the silicon thin film 50 m SHJ cells.