Optical Improvement of ZnO-Coated Glass with New Refractive-Index Matching Layer Inserted at Glass/ZnO Interface

We prepared and applied a-SiO x thin films to hydrogenated microcrystalline silicon solar cells (μc-Si:H) as a front antireflection layer (FAL) in order to reduce optical reflection loss. By inserting the optimized SiO x FAL with a refractive index of ${\sim}1.75$ into the glass/ZnO interface a relative increase in short-circuit current density ($J_{\text{sc}}$) by 5% could be obtained which corresponded to an improved spectral response in the 550--950 nm wavelength regions. In addition, this optimized FAL did not deteriorate the properties of the ZnO layer because no significant changes in open-circuit voltage ($V_{\text{oc}}$) and fill factor (FF) were observed. As a result, the cell with an efficiency of as high as 8.28% ($V_{\text{oc}}=0.495$ V, $J_{\text{sc}}=25.09$ mA/cm 2 , $\mathrm{FF}=0.667$) could be obtained.