Unambiguous distinction between diffusion length and surface recombination velocity of solar cells at different excitation levels

In this work we present a conclusive separation of bulk and surface recombination properties of solar cells. For this purpose, bifacial silicon solar cells were fabricated. The backside differential spectral response of the cells has been measured in the presence of bias light, both with and without backside passivation by means of corona charging on top of a thermal oxide. Employing the common one-dimensional Shockley model, the measurement curves have been simulated. This enables the base diffusion length to be distinguished from the backside surface recombination velocity. As such, their values have been determined individually. Repeating this procedure for different intensities of bias light has yielded the nonlinear behavior of the recombination mechanisms. By applying the Schockley–Read–Hall recombination theory, it was deduced that Fe interstitials presumably are the predominant bulk recombination centers.