Pinhole Dynamics in Textured Passivated-Contact Si Solar Cells

Passivated-Contact Si solar cells are quickly becoming a dominant cell architecture promising high efficiencies over 25%. However, their thin SiOx layer is prone to formation of Si-rich pinholes. Pinholes have a crucial impact on carrier transport, with the potential of even shorting the cell. Therefore, a robust model of pinhole formation is needed to help control their formation. Such models have been already developed for planar cells. In contrast, most modern cells have oxide layers with inverted pyramid, or valley textures. Recent EBIC experiments indicate that pinholes form preferentially in the valley troughs of these textures. Remarkably, no models have been put forward to analyze this strong preference, in spite of its obvious relevance. In this paper we present a detailed analysis of pinhole formation in textured oxides and present compelling evidence that pinholes preferentially form at the valley troughs of the textured oxide layers.