3D Nano-Epitaxial Lateral Overgrowth (nano-ELOG) of Large Area, Highly Efficient, and Flexible Multijunction Solar Cells for Space Applications

By Epitaxial Lateral Overgrowth (ELOG) and Selective Area Growth (SAG) in nanometer scales, MicroLink Devices will develop the next generation of multijunction solar cells for Space applications. The proposed innovation is the first attempt to use advanced surface nano-engineering technologies to control the formation, propagation and annihilation mechanism of extended defects including dislocations in multijunction solar cells. There is significant gap between the theoretically calculated efficiency of multijunction solar cells and the experimental results. That efficiency gap increases with the increase of number of junctions/subcells. Misfit dislocations created due to high lattice mismatch between subcells play a major role in hampering the efficiency and reliability of such devices. A successful implementation of nano-ELOG in solar cells will results in 3J solar cells with significantly reduced dislocation density, resulting in an improved Voc and Isc and conversation efficiencies of the cells. Therefore, MLD can utilize this method to grow devices with increased number of junctions to reach practical efficiencies close to 40% (6J) from the current 30% (in commercially available 3J cells) in AM0 and 1sun conditions. It is important to explore, and consequently, take advantage of the latest nano-patterning developments for NASA's photovoltaic devices.