Ultra-efficient N-junction photovoltaic cells with VOC > 14V at high optical input powers

GaAs phototransducers with 5 to 12 p/n junctions are shown to demonstrate breakthrough performance in optical conversion efficiency ranging from 65% to just under 70%. In particular, for a current-matched 12 junction device we have recorded an efficiency of 66.5% at V
_oc
= 14.46V (open circuit voltage) with an approximately 650 suns / 841 nm monochromatic source. Our simulations reproduce the PV characteristics of the physical devices with good (~ %) accuracy for V
_oc
and I
_sc
(short circuit current), which allows us to numerically study the influence of experimental conditions and design factors on device performance. Moreover, our simulations suggest that measured efficiencies are very close to the theoretical limits of the heterostructures under consideration. Our focus in these proceedings is twofold: a) to present an overview of the results of these experiments as well as b) study the factors which limit simulated device performance with the objective of attaining monochromatic conversions efficiencies exceeding 70%.