Low Cost, High Performance Ultrathin Gallium Arsenide Solar Cells for Terrestrial Photovoltaics
Despite their impressive performance reaching near the theoretical limit, the practical application of gallium arsenide solar cells in on-earth applications remains a formidable challenge largely due to the excessively high cost of growing device-quality epitaxial materials. The research outlined in this proposal aims to address the future energy demand of global society by developing a practical solution that can balance the high performance of gallium arsenide solar cells with their production cost, and therefore enable their large-scale deployment in terrestrial photovoltaics. The highly multidisciplinary themes of the proposed research will be intimately integrated with comprehensive teaching and outreach efforts. PI Yoon will work with the Center for Engineering Diversity at the University of Southern California to establish laboratory internship opportunities for educationally-disadvantaged middle and high school students in the inner city of Los Angeles. Co-PI Lee will partner with Yale Science Outreach on two particular programs: Science on Saturdays for families and the general public and the Pathways to Science program for middle and high school students. Training both undergraduate and graduate student researchers will be a primary educational goal, where the PIs will continue to support and encourage broadening participation of female students and students from underrepresented groups.
The goal of this collaborative research is to demonstrate high performance, cost-competitive GaAs solar cells for their large-scale deployment in terrestrial photovoltaics. To achieve this goal, we will develop novel strategies of materials growth and device fabrication exploiting (1) an ultrathin device platform that enables efficient use of expensive source materials, (2) multilayer epitaxial growth that can significantly reduce the cost of epitaxial materials, (3) bifacial nanophotonic light manipulation that can enhance the absorption, (4) high yield printing techniques that permits large-area distribution over low cost substrates. Specifically, Task 1 will explore the growth of multiple device stacks of ultrathin GaAs solar cells in molecular beam epitaxy (MBE) targeting uniform materials properties and device performance of multilayer-grown epitaxial stacks. Task 2 will seek to establish fundamental understanding and optimization of the epitaxial design for ultrathin GaAs solar cells to enhance the carrier collection and maximize the effectiveness of light trapping. Task 3 will focus on developing integrated schemes of bifacial photon management for light trapping and photon recycling. Successful completion of the proposed research will lead to the development of high performance, economically viable GaAs solar cells for terrestrial applications and also strengthen fundamental understanding of: materials behaviors and dopant diffusion in MBE-grown multilayer epitaxial assemblies; optimized layer structures of ultrathin GaAs solar cells for the most efficient photovoltaic energy conversion; multifunctional optical designs for maximized light absorption in the optically thin absorber.
