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A Novel Method of Optimization at a Constant Desposition Rate: Application to Thin-Film Amorphous Silicon Solar Cells
D. Hrunski, B. Rech, T. Repmann, J. Kirchhoff, A. Gordijn, J. Hüpkes, W. Appenzeller
PECVD, Performance, a-Si:H
Thin Films
Subtopic: Amorphous and Microcrystalline Silicon
Event: 23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session: 3AV.1.36
2292 - 2296
ISBN: 3-936338-24-8
Paper DOI: 10.4229/23rdEUPVSEC2008-3AV.1.36
0,00 EUR
Document(s): paper


To reduce the production cost for thin-film amorphous silicon solar cells, a high deposition rate must be achieved without a decline in the cell efficiency. Over the last few decades, evidence was collected on the deposition rate (Rd) as an additional technological parameter: Y. Hishikawa et al. have demonstrated that when substrate temperature (Ts) is fixed, amorphous silicon material properties appear to depend only on Rd, regardless of the gas pressure, rf power, or reactor dimensions. High-efficiency amorphous single-junction solar cells deposited at a higher deposition rate with no further frequency increases is a goal of the present work. To find a technological optimum, the compared cells should have the same deposition rate and thickness. The novel optimization method of a constant deposition rate (CDR) is proposed. This method means that two technological parameters could be varied during optimization in order to keep the deposition rate constant. Here, the discharge power as the second technological parameter was changed in order to ensure a constant deposition rate. When CDR is applied for two different deposition pressures areas (“low-pressure regime” is 0.5 Torr and “high-pressure regime” is 8 Torr), it allows evidence to be obtained which clearly indicates that solar cells of an almost similar quality could be achieved under rather different technological conditions. Based on this fact, an updated view is presented of the role of silane concentration in plasma as a technological parameter. High initial efficiencies of 10.4 % are achieved by CDR for 1 cm2 amorphous silicon single-junction p-i-n solar cells deposited on Asahi-U-type TCO at a deposition rate of 5 Å/s (i-layer). The optimized solar cells show a stabilized efficiency of 8 %.