The effect of hybrid photovoltaic thermal device operating conditions on intrinsic layer thickness optimization of hydrogenated amorphous silicon solar cells

Citation data:

Solar Energy, ISSN: 0038-092X, Vol: 86, Issue: 9, Page: 2673-2677

Publication Year:
2012
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Repository URL:
http://digitalcommons.mtu.edu/materials_fp/41
DOI:
10.1016/j.solener.2012.06.002
Author(s):
Pathak, M.; Girotra, K.; Harrison, S. J.; Pearce, Joshua M.
Publisher(s):
Elsevier BV
Tags:
Energy; Materials Science; Amorphous silicon; Annealing; Photovoltaic-thermal hybrid; PVT; Solar thermal; Staebler–Wronski effect
article description
Historically, the design of hybrid solar photovoltaic thermal (PVT) systems has focused on cooling crystalline silicon (c-Si)-based photovoltaic (PV) devices to avoid temperature-related losses. This approach neglects the associated performance losses in the thermal system and leads to a decrease in the overall exergy of the system. Consequently, this paper explores the use of hydrogenated amorphous silicon (a-Si:H) as an absorber material for PVT in an effort to maintain higher and more favorable operating temperatures for the thermal system. Amorphous silicon not only has a smaller temperature coefficient than c-Si, but also can display improved PV performance over extended periods of higher temperatures by annealing out defect states from the Staebler–Wronski effect. In order to determine the potential improvements in a-Si:H PV performance associated with increased thicknesses of the i-layers made possible by higher operating temperatures, a-Si:H PV cells were tested under 1 sun illumination (AM1.5) at temperatures of 25 °C (STC), 50 °C (representative PV operating conditions), and 90 °C (representative PVT operating conditions). PV cells with an i-layer thicknesses of 420, 630 and 840 nm were evaluated at each temperature. Results show that operating a-Si:H-based PV at 90 °C, with thicker i-layers than the cells currently used in commercial production, provided a greater power output compared to the thinner cells operating at either PV or PVT operating temperatures. These results indicate that incorporating a-Si:H as the absorber material in a PVT system can improve the thermal performance, while simultaneously improving the electrical performance of a-Si:H-based PV.