Optimization of substrate thickness for interdigitated back contact silicon solar cells

A computer model for the computation of the optimum substrate thickness of interdigitated-back-contact (IBC) Si solar cells is developed and demonstrated. The one-dimensional model assumes that solar-cell quantum efficiency is fully determined by minority-carrier diffusion length, surface recombination velocity, and substrate thickness, and hence unaffected by back-diffused layers. The maximum thickness allowable for a 10-percent reduction in short-circuit current density can also be determined. Optimum and maximum-allowable thicknesses are plotted as functions of diffusion length for different recombination velocities, using input parameters typical of lightly doped n-type and p-type backlit IBC cells under AM 1.5 illumination at 300 K. Good agreement is found with empirical parameter values determined by curve fitting.