22nd June 2016

NSF SBIR Phase I: Luminescent Solar Concentrating Glass Window Quantum Dot Coatings

This SBIR Phase I project develops a technology called luminescent solar concentration that will 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 yet because previous tint materials typically absorb their own emitted light, limiting efficiency. This project aims to provide a solutions to these problems with a novel low-cost window tint material made from quantum dots. The work conducted in this project focuses on discovering new improvements in efficiency and cost reduction of the quantum dots. 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 coal needed to generate electricity. The technical innovation in this project is the development of an ideal window-tint material that will be used to transform windows into electricity generating components of urban buildings. Luminescent solar concentrators 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 photoluminescent dyes typically have strong self-absorption, narrow spectral absorption, and poor stability. Quantum dots, which are interesting due to their easily tunable light emission, are more stable, but are expensive, 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 optimized for low-cost commercial solar cells, and do not self-absorb. In this SBIR Phase I project CuInSeS/ZnS quantum dots will be optimized for higher photoluminescence efficiency >50% and applied as industry-compatible coatings to glass substrates for higher performance. See the details here.