Theoretical optimization of double dielectric back reflector layer for thin c-Si based advanced solar cells with notable enhancement in MAPD

Abstract

Dielectric layers on the back surface of a solar cell not only enhance the back reflection but also contribute to better light management by minimizing the absorption loss that happens for conventional back metal contacts. Considering the critical applications of back dielectric layers in solar photovoltaic (PV) technology, their physical characteristics must be optimized, which is the goal of this present investigation. Thin (~30 μm) c-Sibased advanced solar cells that are gradually drawing the attention of modern PV technology; have been chosen as the typical case here. Theoretical optimization of thickness-dependent light reflection capabilities for two different types of dielectric stacks, namely, SiO2/Al2O3 and HfO2/Al2O3 have been carried out. COMSOL Multiphysics™ simulator based on the finite element method (FEM) numerical solution technique has been used. The electromagnetic wave frequency domain (EWFD) module has been used for computational purposes. The back layer engineering using double dielectric back reflector layers has been carried out to overcome the light transmission losses that are usually prevalent in thin (~30 μm) c-Si solar cells at longer wavelengths. Such analyses are of immense importance for thin c-Si based PERC solar cells also. The carrier generation rate, external quantum efficiency (EQE), and maximum achievable photocurrent density (MAPD) have been measured for the optimized cell structures that resulted in a significant increment in each of the parameters. This makes such back reflecting structures worth implementing in thin c-Si based advanced solar cells to minimize the transmission losses at longer wavelengths.