Collaborative Research: Highly mismatched GaSb-GaAs thin film multijunction solar cells

Rochester Institute Of Tech, Rochester NY

Investigators

Abstract

Abstract: Non-Technical: Rochester Institute of Technology and University of California Los Angeles propose to demonstrate a highly mismatched, Sb-based multi-junction solar cell with low defect density and optimal bandgaps, with efficiency over 50%. A novel growth technique known as interfacial misfit array will be used to develop the proposed solar cell devices. These devices would be capable of revolutionary advances in efficiency and perhaps the eventual possibility of transferring the high efficiency III-V technology to a low cost Si substrate. The proposed work will significantly reduce multi-junction solar cell cost and at the same time increase energy conversion efficiency. As well, the proposed material growth methods can have potential impact on areas such as detectors, lasers and memory devices. This work will also support the development of educational activities at multiple levels. Both graduate and undergraduate students will receive training in leading-edge materials engineering and device physics. As well, both principle investigators will be involved in high school student summer mentoring in their laboratories, through a series of lectures and demonstrations involving the relationship between materials and solar energy conversion. Technical: The technical aim of this proposal is to gain access to near optimal band gaps for a five junction solar cells by integrating Sb-based materials into the lattice matched InGaP2/GaAs technology using the GaSb interfacial misfit growth technique. Interfacial misfit growth will allow for the lattice-mismatched growth of high quality GaSb on GaAs without the need for a complex and growth intensive step-grade buffer layer. Proposed devices will be comprised of lattice matched (Al)InGaP2, AlGaAs and GaAs as the top three cells, a single interfacial misfit transition and lattice matched 1.1 eV AlGaSb and 0.73 eV GaSb as the bottom two cells. Team members have already demonstrated the interfacial misfit growth of GaSb, which allows them to achieve the lattice-mismatched growth of high quality materials on GaAs, without the need for a complex and growth intensive step-grade buffer layer. In the first year, AlGaSb on GaSb/GaAs templates and InGaP on GaAs substrates along with required tunnel junctions will be developed, with the aim of understanding of optical and electrical properties. In the second and third years, the proposed three junction and five junction solar cells will be developed. All of the steps will be supported by detailed materials characterization as well as physics-based device simulations, to optimize the device design and imporve the predictiave capabilites for Sb-based optoelectronics devices.