Extended FF and V-OC Parameterizations for Silicon Solar Cells

This work is concerned with maximal and currently obtained fill factors of crystalline silicon solar cells. Recent research activities have led to a drastically decreased recombination in the volume as well as at the surfaces and interfaces of crystalline silicon solar cells. As a result, open-circuit voltages (V-OC) and fill factor (FF) values increased significantly. In order to classify how good the achieved improvements are, it is necessary to know the maximum achievable values. Unfortunately, there is no explicit expression for the FF in terms of other characteristic solar cell parameters. For this reason, the empirical FF0-relation by Green is widely used to predict upper FF bounds for a given V-OC. In order to evaluate to what extent Green's relation is a good approximation to recently obtained values, we study FF-V-OC relations for ideal resistance-free single junction silicon solar cells limited by intrinsic recombination using state-of-the-art analytical models. The obtained upper bounds are compared with recently published record values showing that all values stay below the intrinsic limit. We provide parameterizations of V-OC and FF as a function of sample thickness w and base dopant density N-dop.

Automated summary

This work focuses on the maximal and currently obtained fill factors of crystalline silicon solar cells. Recent research has significantly reduced recombination in the volume, surfaces, and interfaces of these cells, leading to increased open-circuit voltages and fill factor values. In order to evaluate the extent of these improvements, it is necessary to know the maximum achievable values. Analytical models were used to study the FF-V-OC relations for ideal resistance-free single junction silicon solar cells limited by intrinsic recombination, and the obtained upper bounds were compared to recently published record values. All values were found to be below the intrinsic limit.