Advanced light management in Micromorph solar cells

In this study recent results of Micromorph thin film silicon tandem cells with n-doped silicon oxide based intermediate reflectors deposited in the KAI-M industrial PECVD reactor are discussed. From the optical analysis of the devices, specific features in the reflection spectrum attributed to the incorporated intermediate reflector can be observed. In particular, the influence of the Transparent Conductive Oxide (TCO) layer roughness on the reflection spectrum of the cells is studied. Compared to commercial SnO2, reflection losses are reduced and photocurrents are increased by using rougher front TCO-layers like LPCVD-ZnO which should lead to potentially higher efficiencies at same silicon absorber thicknesses. Micromorph tandem cells with intermediate reflector on ZnO leads to 10.18% efficiency after 1000 h of light-soaking, whereas 10.35% have been achieved on commercial SnO2.