Determination of metal contact recombination parameters for silicon wafer solar cells by photoluminescence imaging

In order to reliably extract metal-silicon interface recombination parameters to aid optimization of silicon wafer solar cell designs, a test metallization pattern with regions of varying front metal contact fractions is screen printed to create special test cells, alongside solar cells with a standard H-pattern print. Both the test pattern and H-pattern cells are analyzed using intensity-dependent photoluminescence imaging (Suns-PL), and the H-pattern cells are additionally probed at each busbar to monitor their open-circuit voltage (via Suns-Voc measurements). The resultant data are analyzed in two ways, the first being a simple four parameter graphical fitting to the Suns-PL plots of the regions of interest, and the second being a detailed finite element method (FEM) based simulation and numerical fitting. By accounting for the lateral balancing currents in the FEM based simulation, test patterns with imaginary isolation across the edges of the mini cells could be used, which were the easiest to fabricate. The FEM method is more rigorous and is able to replicate simultaneously the Suns-PL characteristics of both test pattern and H pattern cells, using a common set of recombination parameters.