Modeling nonuniform irradiance and chromatic aberration effects in a four junction solar cell using SPICE

A two-dimensional, distributed resistance model for a four junction solar cell is implemented in SPICE. Efficiency estimates for Gaussian irradiance profiles with different peak-to-average ratios (PAR) are determined via grid optimization at concentrations of 500, 1000 and 2000 suns. Optimizing finger spacing for a PAR of 6 improves cell efficiency by 1.8% (absolute) at 2000 suns compared to that observed from finger spacing optimized for a uniform illumination. To address the impact of chromatic aberration on cell efficiency, a CPV system is modeled in Zemax for a geometric concentration of 1250X. Using a finger spacing optimized for uniform irradiance at the average optical efficiency of 82%, the neglect of chromatic aberration was found to overstate system efficiency by 3% (absolute).