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Embedded CdS nanowires are used for improving the spectral transmission of the CdS window layer, thus enhancing the quantum efficiency of CdS-CdTe solar cells. Substantially higher light transmission is observed in the 300nm-550nm wavelength range. A nearly ideal spectral response of quantum efficiency over a wide spectral range provides evidence for improved light transmission through the window layer and enhanced absorption and carrier generation in the CdTe absorber layer. Nanowire CdS/CdTe solar cells on SnO 2 /ITO-soda lime glass substrates, and with Cu/graphite paste/silver paste as back contact electrodes, yield a power conversion efficiency of 12%. MoO 3-x /Au back contacts were also investigated. With these back contacts, the nanowire CdS-CdTe solar cells exhibit efficiency comparable to the efficiency of their planar CdS counterparts. Junction transport mechanisms are delineated for advancing the basic understanding of device physics at the interface. Our results prove the efficacy of this nanowire approach for enhancing the quantum efficiency in window-absorber type solar cells (CdS-CdTe, CdS-CIGS and CdS-CZTSSe etc.) and other optoelectronic devices.

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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