Automated design of multi junction solar cells by genetic approach : reaching the >50% efficiency target

The proper design of the multi-junction solar cell (MJSC) requires the optimisationsearch through the vast parameter space, with parameters for theproper operation quite often being constrained, like the current matchingthroughout the cell. Due to high complexity number of MJSC device parametersmight be huge, which makes it a demanding task for the most ofthe optimising strategies based on gradient algorithm. One way to overcomethose difficulties is to employ the global optimisation algorithms based onthe stochastic search. We present the procedure for the design of MJSCbased on the heuristic method, the genetic algorithm, taking into accountphysical parameters of the solar cell as well as various relevant radiative andnon-radiative losses. In the presented model, the number of optimising parametersis 5M + 1 for a series constrained M-junctions solar cell. Diffusiondark current, radiative and Auger recombinations are taken into accountwith actual ASTM G173-03 Global tilted solar spectra, while the absorptionproperties of individual SCs were calculated using the multi band k · pHamiltonian. We predicted the efficiencies in case of M = 4 to be 50:8%and 55:2% when all losses are taken into account and with only radiativerecombination, respectively. Keywords: Multi Junction Solar Cells, Current Matching, III-Vsemiconductors, Auger effect, Genetic Algorith