STTR Phase I: High Efficiency Thin-film Photovoltaics on Low-cost Substrates by Layer Transfer

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This Small Business Technology Transfer Phase I project will apply high aspect ratio, nm-scale, columnar, and crystalline Si structures as templates for high-quality growth of thin-film GaAs solar cells on low-cost flexible substrates. Sub-10-nm Si seed layers are expected to facilitate growth of low-defect density GaAs films. The aspect ratio of nm-scale structures also serve as sacrificial layers for removal of completed GaAs solar cell. Epitaxial growth and characterization of GaAs films on nm-scale Si structures will be carried out at the Center for High Technology at the University of New Mexico. Successful phase I STTR research will lead to commercialization of high (~ 20 %) efficient, flexible solar cells for applications in a wide range of terrestrial and space environments. Multiple substrate re-use and inherent large area processing capability of Si will result in significant cost reductions. High quality heteroepitaxial GaAs growth on Si has been a subject of intense research. Due to its direct bandgap, GaAs is attractive for a number of optoelectronics applications and its integration with Si-based microelectronics has been a cherished goal. The lattice and thermal expansion mismatches with Si make it difficult to grow good device quality layers. We have recently demonstrated as the Si seed dimension is reduced below 100 nm dimensions, the quality of heteroepitaxial growth increases rapidly. The nm-scale Si structures are formed using low-cost, large area methods based on conventional integrated circuit processing methods. Successful research effort will lead to reduction in PV generation costs, and enhanced applicability of thin-film PV in terrestrial and space environments because in contrast with competing thin-film solar cells, GaAs thin-film solar cells will not suffer from light-induced performance degradation.