Loss Analysis of High-Efficiency Back-Contact Back-Junction Silicon Solar Cells

Abstract

This work presents a model to assess the loss mechanisms of back-contact back-junction (BC-BJ) silicon solar cells fabricated at Fraunhofer ISE. It describes the three main loss mechanisms in our BC-BJ solar cells: the series resistance, the optical losses and the recombination losses and their influence on the cell efficiency. The several calculations are based on a simplified quasi-one-dimensional analytical model for the series resistance, a ray tracing simulation for the optical losses and analytical and numerical simulations for the recombination losses. Experimental measurements of the specific losses are in a good agreement with the modeled values. The reduction of the cell efficiency due to the three processes was determined to be 3.29 % abs. due to recombination processes, 1.95 % abs. due to optical losses and 0.24 % abs. due to series resistance effects. Hence the theoretical achievable cell efficiency for the actual cell design is predicted to be 22.89 % in comparison to the best measured cell result of 21.3 %.