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designed light trapping structure implemented by cheap and common material SiO2. Such a light trapping structure  based on SiO2 is so employed that can avoid parasitic absorption.  However, ultra-thin semiconductor layers are less effective at absorbing sunlight, unless smart light-trapping techniques can be designed and implemented. Such techniques aim at increasing the optical path of light in the semiconductor, which enhances the absorption efficiency for the same material thickness.  100nm of direct bandgap materials such as amorphous silicon (a-Si), cadmium telluride (CdTe), or copper indium gallium diselenide (CIGS) could be adequate to realize thin-film photovoltaic cells with integrated absorbance close to the maximum value. improve light absorption in the absorber layer by  increasing the optical path length, one method has utilized back reflectors in the bottom of  cells to reflect the light back into the absorber layer.  The modified structure has a new or an  extra layer (ZnO) in between TCO and CdS to obtain better  performance and thus it can be said that the front contact  consists of TCO and a buffer layer (ZnO).  To prevent this undesired  forward leakage current a high resistive buffer layer of ZnO  was inserted in between the front contact TCO and CdS  window layer  20.27% (Voc = 1.08 V, Jsc = 24.93 mA/cm2,FF = 0.83).    Prospects of novel front and back contacts for high efficiency cadmium telluride thin film solar cells from numerical analysis