Improving solar cell efficiency with optically optimised TCO layers

In this paper we analyse the capabilities and limitations of single layer index matching coatings for the glass/TCO or TCO/absorber interfaces in thin film solar cells. Optical models are used to evaluate the potential gain in cell efficiencies with hypothetical ideal matching materials to minimise losses due to reflections at internal interfaces. We suggest the range of desired optical properties of such materials, where a net gain in cell efficiency can be achieved, and discuss the commercial benefits of such intermediate matching layer. For some selected ternary and quaternary novel oxides available, the potential efficiency gain due to the inclusion of an anti-reflective matching layer in a solar cell structure is calculated and compared with the case of ideal matching materials.

► We show an analytic expression for efficiency increases of internal AR-layers. ► The tuning of a TCOs refractive index to act as such an AR layer is demonstrated. ► Solar cell efficiency can be increased by 15% with optically tuned interfaces. ► We compare our model with the results of existing AR-layers of SiOxSiOx and rough interfaces.