Current Mismatch and Luminescence Coupling in Three-junction Photonic Power Converters with and without Back Reflector

In this work the coupling process efficiency in three-junction photonic power converters based on GaAs/AlGaAs rear-heterojunction subcells is experimentally quantified. A coupling process efficiency of 32 % ± 9 % from top and middle subcells to the limiting bottom subcell is found. Furthermore, it is shown experimentally how a back reflector affects luminescence coupling in multi-junction photonic power converters by re-directing photons that are emitted by the bottom subcell towards the upper subcells.