Project Name: Tandem Solar Cells: Pathway to Low-Cost, High-Efficiency Photovoltaics
Funding Opportunity: PVRD
SunShot Subprogram: Photovoltaics
Location: Columbus, OH
SunShot Award Amount: $1,124,999
Awardee Cost Share: $179,286
Project Investigator: Tyler Grassman

This project is developing a tandem solar cell with gallium arsenide phosphide (GaAsP) on silicon (Si) aimed at an efficiency of at least 30%. The cell will be produced using highly scalable and manufacturable processes, which will be accomplished through optimization of the current prototype cell, including the demonstration of innovative structures that are ideally suited for maximized Si-based tandem manufacturing. A mature GaAsP/Si tandem cell could then be manufactured at scale via existing Si and III-V tooling and infrastructure, greatly reducing capital expenditures and revitalizing existing manufacturing industries.


The research team will build on its first demonstration of the GaAsP/Si tandem cell with approximately 20% efficiency by optimizing the current GaAsP/Si prototype cell to reach 30% efficiency. The tandem will incorporate state-of-the-art Si bottom cell device designs optimized for the tandem architecture and optimized GaAsP top cell using well-controlled epitaxy of III-V layers on Si, novel defect-tolerant device designs, and tunnel junction developed for materials with a slight lattice mismatch. The team will transition the fabrication of cells to industrially relevant methods to enable low-cost, scalable processing and manufacturing.


High-efficiency tandem cells on silicon promise to dramatically improve the performance of single-junction silicon cells at a small additional cost, but are yet to be demonstrated. This project will develop and demonstrate a high-efficiency GaAsP/Si tandem solar cell for application to one-sun and low-concentration systems, produced using highly scalable and imminently manufacturable processes, positioned for near-term market impact. Cell efficiencies of 30% will lead to reduction in balance of system costs and decrease overall installed system costs, accelerating the solar levelized cost of energy beyond the SunShot 2020 target.