The effects of high temperature processing on the structural and optical properties of oxygenated CdS window layers in CdTe solar cells

Journal Article · Mon Jul 28 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4891235· OSTI ID:22308563

Paudel, Naba R.; Grice, Corey R.; Xiao, Chuanxiao; Yan, Yanfa ^[1]

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1. Department of Physics and Astronomy, and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606 (United States)

High efficiency CdTe solar cells typically use oxygenated CdS (CdS:O) window layers. We synthesize CdS:O window layers at room temperature (RT) and 270 °C using reactive sputtering. The band gaps of CdS:O layers deposited at RT increase when O{sub 2}/(O{sub 2} + Ar) ratios in the deposition chamber increase. On the other hand, the band gaps of CdS:O layers deposited at 270 °C decrease as the O{sub 2}/(O{sub 2} + Ar) ratios increase. Interestingly, however, our high temperature closed-space sublimation (CSS) processed CdTe solar cells using CdS:O window layers deposited at RT and 270 °C exhibit very similar cell performance, including similar short-circuit current densities. To understand the underlying reasons, CdS:O thin films deposited at RT and 270 °C are annealed at temperatures that simulate the CSS process of CdTe deposition. X-ray diffraction, atomic force microscopy, and UV-visible light absorption spectroscopy characterization of the annealed films reveals that the CdS:O films deposited at RT undergo grain regrowth and/or crystallization and exhibit reduced band gaps after the annealing. Our results suggest that CdS:O thin films deposited at RT and 270 °C should exhibit similar optical properties after the deposition of CdTe layers, explaining the similar cell performance.

• OSTI ID: 22308563
• Journal Information: Journal of Applied Physics, Vol. 116, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
ANNEALING
ATOMIC FORCE MICROSCOPY
CADMIUM SULFIDES
CADMIUM TELLURIDES
CRYSTALLIZATION
CURRENT DENSITY
DEPOSITION
EFFICIENCY
ELECTRICAL FAULTS
LAYERS
OPTICAL PROPERTIES
SOLAR CELLS
SPUTTERING
SUBLIMATION
TEMPERATURE RANGE 0273-0400 K
THIN FILMS
VISIBLE RADIATION
X-RAY DIFFRACTION