Enabling High-Efficiency InAs/GaAs Quantum Dot Solar Cells by Epitaxial Lift-Off and Light Management

Tandem solar cells overcome conversion efficiency limitations of conventional single-junction solar cells by using multiple absorber materials with different band gap energies. The absorber materials are stacked in sequence with decreasing band gap energy, thus reducing thermalization losses in the conversion process. The improved conversion efficiency of a tandem solar cell comes at increased fabrication complexity and, hence, production cost. More fabrication steps and more materials are needed to produce a tandem solar cell than to produce a single-junction solar cell. Economically, a tandem solar cell is of interest if it generates electricity at a lower cost than either of its comprising single-junction counter parts. In this paper we present cost relations that link the costs and efficiencies of two single junction solar cells to those of a dual-junction tandem solar cell made from the combination of the two cells. In doing so, we establish criteria under which tandem solar cells are economically viable.