SBIR Phase I: Low-Cost, Nanoepitaxial Lateral Over-Growth for III-V Metamorphic Solar Cells

This Small Business Innovation Research (SBIR) Phase I project aims to substantially reduce the cost of multijunction solar cells for terrestrial concentrator photovoltaic (CPV) solar power generation. The presently favored type of solar cell for CPV applications is the inverted metamorphic multijunction (IMM), which offers the highest conversion efficiency. However, the thickest and most costly single region of this cell is the buffer layer, which provides a transition in the lattice constant between subcells, but does not contribute to current generation. Plus, the metamorphic subcell, which is grown on the buffer layer, is adversely affected by defects which originate in the buffer layer. In this project, the buffer layer will be replaced with a nanopatterned layer, which will allow the metamorphic subcell to form in a short distance with few defects. The broader/commercial impact of this project will be the potential to provide a new technique to fabricate IMM solar cells, allowing a significant cost reduction. IMM solar cells are a key component of terrestrial CPV solar power generators and account for a substantial fraction of their cost. A reduction in the cost of IMM cells should therefore lower the cost of solar-generated electricity. This approach is expected to achieve a 50% reduction in growth time and a 30% reduction in the bill of materials (BOM) of IMM cells.