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 300 nm-550 nm 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 SnO2/ITO-soda lime glass substrates, and with Cu/graphite paste/silver paste as back contact electrodes, yield a power conversion efficiency of 12%. MoO3-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. (C) 2015 Elsevier B.V. All rights reserved.