Micro-Transfer Printer-Assembled Five Junction CPV Microcell Development

We have developed multijunction solar cells on both GaAs and InP platforms to split the solar spectrum efficiently among subcells that maintain lattice-match to their respective source substrates. The GaAs-based dual-junction solar cell has achieved 31% AM1.5D concentrator efficiency. The InP-based triple junction solar cell has achieved 8.7% AM1.5D efficiency under concentration. Using micro-transfer printing, the wide-bandgap GaAs-based subcells will be stacked on top of the narrow-gap InP-based subcells and characterized to determine 4-terminal AM1.5D efficiency of the five-junction device. The microcells, less than 200 μm on a side, are assembled on transparent glass substrates, permitting diffuse light transmission to be collected by a silicon backplane. The approach facilitates efficient collection of both direct and diffuse sunlight for potential applications in a wide variety of climates. Major milestones in III-V device development are detailed.