A drift-diffusion solver using a finite-element method to analyze carrier dynamics at ultra-high solar concentrations

Emily S. Carlson, Margaret Stevens, David B. Emerson, Xiaozhe Hu, James H. Adler, Thomas E. Vandervelde

Abstract: We present a drift-diffusion and Poisson solver using a finite-element method to study carrier dynamics under ultra-high solar concentration. By modeling the carrier densities and the electric potential in quasi steady-state and dynamic conditions, we can use the splitting of the quasi-Fermi levels to model electrical properties such as open-circuit voltage. In this work, we analyze the validity of previously used approximations on open-circuit voltage and the effects of increasing optical carrier densities on small band gap solar cells. Graded mesh refinement is implemented to improve runtime. Ultimately, we show a change in the carrier profiles that may lead to detrimental charge carrier extraction.