Sunlight, undoubtedly, is the future source of energy for humans. The current conversion technologies of sunlight to electricity using photovoltaic technologies are still moderate and relatively costly. The multi-junction photovoltaic cell design offers the highest achieved conversion efficiency that already exceeded the 40%. This work aims for maximizing the conversion of the sunlight for terrestrial application using the series-multi-junction photovoltaic cells by an optimal choice for the bandgap energies. (C) 2013 Elsevier Ltd. All rights reserved.