Monolithic, Ultra-Thin GaInP/GaAs/GaInAs Tandem Solar Cells

We present here a new approach to tandem cell design that offers near-optimum subcell bandgaps, as well as other special advantages related to cell fabrication, operation, and cost reduction. Monolithic, ultra-thin GaInP/GaAs/GaInAs triple-bandgap tandem solar cells use this new approach, which involves inverted epitaxial growth, handle mounting, and parent substrate removal. The optimal ~1-eV bottom subcell in the tandem affords an ~300 mV increase in the tandem voltage output when compared to conventional Ge-based, triple-junction tandem cells, leading to a potential relative performance improvement of 10-12% over the current state of the art. Recent performance results and advanced design options are discussed.