For improving the photovoltaic performance of CdS/CdTe thin film solar cells, the US window layer is one of the most crucial factors. Here we demonstrate the photovoltaic performances of the low-environmental-load CdS/CdTe solar cell employing the US layer doped with various metal organic (MO) compounds, i.e., (CH3)(2)SnCl2, (C6H5)(3)GeCl, (CH3CO2)(3)In, [(C2H5)NCS2](2)Zn. Due to the MO doping, the degree of (111) preferential orientation of CdTe on the US layer is improved remarkably, influencing the increases in V-oc and F.F. Being almost independent of the kind of the MO compounds, the short circuit current increases due to increasing optical transmittance of the MO-doped US layers. As a result, utilizing MO-doped US, we have achieved the conversion efficiency of 15.1 %. (c) 2006 Elsevier B.V. All rights reserved.