The influence of monolithic series connection on the efficiency of GaAs photovoltaic converters for monochromatic illumination

This paper presents a theoretical study of the performance and optimization of monolithically series connected GaAs photovoltaic converters under homogeneous monochromatic illumination. The effects of base resistance, perimeter recombination, and isolation trench optical losses on device efficiency are especially highlighted. All the calculations are made for values of the number of individual photovoltaic converters connected in series, n, of 1 (such is the case of a conventional GaAs photovoltaic converter without monolithic connection) 2, 3, and 6. The results show that the losses in monolithic connection can be minimized by means of an increase in device area together with the inclusion of a highly doped lateral conduction layer, and that monolithic connection does not lead to a greater immunity from high series resistance relative to a conventional photovoltaic converter (as stated in literature). The maximum efficiencies predicted are 60.2, 58.9, 58.5, and 57.5% for n=1, 2, 3, and 6, respectively, for an illumination power density of between 10 and 20 W/cm² and a wavelength of 830 nm. Nevertheless, if a dc-dc converter is considered to boost the voltage of an n=1 GaAs photovoltaic converter (with losses associated to this circuit usually of 20%), its maximum efficiency drops to 48.2%