A multi-step superlattice solar cell with enhanced subband absorption and open circuit voltage

In the report, we propose a multiple stepped superlattice (MS-SL) structure, in which GaAs stepped-potential layers are sandwiched between strain-balanced InGaAs wells and GaAsP barriers, for photovoltaic application. Comparison between the normal SL cell and MS-SL cell indicate that the step design in MS-SL cell enhanced sunband absorption to the host bulk material, while reduced overall recombination loss, exhibited a surprising advantage over SL cell in conversion efficiency. According to experimental results, discussions have been made on the competition process between carrier recombinations and carrier escape kinetics from the wells.