SBIR Phase II: Quantum Dot-Tinted Glass Luminescent Solar Concentrator Windows

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase II project is to extend the function of windows by turning them into daytime sources of electricity. The target market for this technology is tall buildings in urban areas, where electricity demand is the highest and the available space for installing solar cells is smallest. This technology utilizes a window tint that can absorb sunlight and remit light of a certain color through the window's glass to small solar cells located at the edges. This technology hasn't been commercialized previously because most tint materials typically absorb their own emitted light, limiting efficiency. This project will provide a novel solution to these problems with a low-cost window tint material made from quantum dots. The work conducted in this project focuses on scaling up prototypes and optimization for cost and reliability. With this technology, tall buildings will approach net-zero energy consumption or even supply electricity to the grid. This would reduce the city's carbon footprint as well as save money for the companies/individuals occupying these buildings, which would increase their prosperity and welfare. This technology would also reduce pollution by limiting the amount of burned fossil fuels needed to generate electricity.  The proposed project develops and scales up the electricity-generating window prototypes to the square meter size, validates long-term reliability, optimizes for manufacturing, and launches pilot projects. The technology is based on luminescent solar concentrators, which are made by tinting a window with a fluorophore material that partially absorbs sunlight and then converts it to fluorescence, preferably in the near-infrared. The fluorescence is trapped inside the window by total internal reflection and is concentrated to the edges where small solar cells efficiently convert that light into electricity. Utilizing this technology in windows to generate electricity has not been commercialized due to unsuitable fluorophores. The fluorophore used in this project are quantum dots composed of CuInSeS/ZnS, which solves the problems of previous materials. Traditional fluorophores like dyes typically have strong self-absorption, narrow spectral absorption, and poor stability. Quantum dots are more stable, but are expensive, sometimes toxic (due to heavy metals), and also suffer from self-absorption. The breakthrough in CuInSeS/ZnS quantum dots is that they are significantly cheaper, avoid toxic elements, have near-infrared fluorescence optimal for low-cost commercial solar cells, and do not self-absorb. At the conclusion of the phase II project, prototype products will be installed in at least one building.  This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.