Edge recombination analysis of silicon solar cells using photoluminescence measurements

Edge losses in silicon solar cells are becoming more important in current photovoltaic research, especially in shingled cell modules with high perimeter to area ratios. Hence, in this study a new approach is presented to quantify edge recombination losses by using photoluminescence (PL) measurements combined with device modelling. The main focus of this work is to determine and separate the contribution of the two relevant edge recombination losses: (i) recombination at the bulk edge, described by an effective surface recombination velocity S_eff,edge, and (ii) recombination at the pn-junction edge, described by an edge-length specific non-ideal recombination parameter J_02,edge. For this purpose, the PL gradient towards the edge at different illumination intensities is fitted by Quokka3 simulations. The developed method is applied for differently separated unpassivated edges, namely by thermal laser separation (TLS) and by mechanical cleaving. Additionally, an emitter window for the TLS edge is introduced where no pn-junction at the edge is present. It was found that the emitter window results in less edge recombination while having the same bulk-edge recombination properties as without. As a result, J_02,edge = 3 nA/cm and S_eff,edge = 10⁵ cm/s are determined for the TLS edge without emitter window while the mechanically cleaved edge showed higher edge recombination.