Simulation and performance optimization of GaAs/GaSb tandem solar cell

Abstract

Multi-junction solar cells provide the highest efficiencies. Intense research activity is being held with the aim to increase the actual performance reached by these cells. Harvesting most of the solar spectrum and finding the optimum design variables in terms of structural parameters and carrier concentrations are the main topics being investigated by solar developers. The GaAs/GaSb based dualjunction solar cell was found suitable for the best absorption of solar spectrum. In this work, an optimization approach was applied to fix the optimal parameters of the top base layer of this structure that provide the maximum efficiency. To achieve this, a series of numerical simulations were carried out by means of Silvaco ATLAS software under standard AM1.5G spectrum where thicknesses and doping levels of the top base layer were varied. The obtained optimal structure yields a power conversion efficiency of 41.65% with open circuit voltage of 1.78 V, short circuit current of 35.72 mA / cm2 and fill factor of 90.16%. The performance of the GaAs/GaSb dual-junction solar cell was further improved by using sunlight concentration. A conversion power efficiency of 45.78% at 60sun light concentration was attained. It was found also that above this level of concentration ratio the detriment effect of shunt resistance dominates.