For improving the photovoltaic performance of CdS/CdTe thin film solar cells, the CdS 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 CdS layer doped with various metal organic (MO) compounds, i.e., (CH 3 ) 2 SnCl 2 , (C 6 H 5 ) 3 GeCl, (CH 3 CO 2 ) 3 In, [(C 2 H 5 ) 2 NCS 2 ] 2 Zn. Due to the MO doping, the degree of (111) preferential orientation of CdTe on the CdS 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 CdS layers. As a result, utilizing MO-doped CdS, we have achieved the conversion efficiency of 15.1%.