Alternative Strategies for Maximizing the Output of Multi-Junction   Photovoltaic Panels
  Multi-junction photovoltaics provide a logical method of increasing the utilization of solar power for a given area. However, their current design and fabrication methods invoke numerous material and cost complexities that limit their potential, particularly for flat panel paradigms. In this paper, three general strategies based on the electrical isolation of the internal sub-layers are described. These strategies involve current or voltage matching the sub-layers by varying of fractional absorption and areal coverage of individual cells within each sub-layer, as well as modifying their combined output using power electronics. A simplified theoretical description of these strategies is provided for pairs of junction materials that allows a more streamlined description of the requirements. 
Ze'ev R. Abrams
physics.optics