Using a 10 nm thick molybdenum oxide (MoO3-x) layer as a transparent and low barrier contact to p-CdTe, we demonstrate nanowire CdS-CdTe solar cells with a power conversion efficiency of 11% under front side illumination. Annealing the as-deposited MoO3 film in N2 resulted in a reduction of the cell's series resistance, from 9.97 Ω/cm2 to 7.69 Ω/cm2, and increase in efficiency from 9.9% to 11%. Under illumination from the back, the MoO3-x/Au side, the nanowire solar cells yielded Jsc of 21 mA/cm2 and efficiency of 8.67%. Our results demonstrate use of a thin layer transition metal oxide as a potential way for a transparent back contact to nanowire CdS-CdTe solar cells. This work has implications toward enabling a novel superstrate structure nanowire CdS-CdTe solar cell on Al foil substrate by a low cost roll-to roll fabrication process.

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Published in Scientific Reports, v. 5, article 14859, p. 1-7.

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This work was supported in part by grants from the National Science Foundation, (NSF-NIRT-ECS-0609064) and (NSF-EPCOR EPS-0447479), Department of Energy/Kentucky Renewable Energy Consortium (DE-FG36-05G085013/ULRF 05-1231G, (NSF-EPS-0447479) and by grants from the Kentucky Science and Engineering Foundation, (KSEF–148-502-02-27, KSEF- 148-502-03-68).

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Figure 1

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Figure 2

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Figure 3: Normalized relative EQE of the nanowire CdS/CdTe solar cells on intrinsic SnO<sub>2</sub>/ITO/Soda-lime glass substrate.

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Figure 4: J-V curves of nanowire CdS-CdTe solar cells with as deposited MoO<sub>3</sub>/Au back contacts under front side illumination, annealing MoO<sub>3</sub>/Au back contacts under dark, front side and back side illuminations.

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Figure 5: Energy Band Discontinuities between the CdTe absorber and the MoO<sub>3−x</sub>/Au back contact layers.