Light Management via Polymers for a Highly Efficient Luminescent Solar Energy Concentrator

The increasing worldwide demand for energy has resulted in a strong push for low-cost alternatives to oil, gas and coal. Solar energy has advantages over other sustainable energy sources (such as wind and biomass) in that it is reliable, quiet, and ever-present. The limited use of this abundant energy resource is the result of the high costs of solar energy conversion by silicon-based photovoltaic (PV) cells. This project involves the dramatic reduction of the cost of solar energy through using large area, luminescent solar energy concentrators (LSCs) in combination with small area PV cells. The concentrators are thin, plastic sheets coated with microlenses, selective reflectors and oriented, luminescent molecules. The lumophores absorb sunlight, and emit it at a longer wavelength in specific directions within the waveguiding mode of the plastic sheet. A small area PV cell is placed at the edge of the waveguide which converts the concentrated sunlight into electricity. The area of the high-cost PV is reduced by more than 90% resulting in a major reduction in module price and price per unit Watt is obtained. As part of this project, several innovations are proposed to improve the performance of the passive sunlight collectors by reducing surface and re-absorption losses: 1) tilted lumophore layers to efficiently direct the light into the waveguide, 2) organic, paintable wavelength-selective mirrors to trap the emission of light within the waveguide, 3) microlenses for focusing light on printed islands of dye to reduce reabsorption, and 4) waveguides with refractive index gradients for minimizing light loss. I also propose an active LSC using switchable dye systems to make a smart window allowing simultaneous electricity generation and room shading. It is expected these features will lead to LSC systems with an overall efficiency of 8-15% when coupled to an appropriate PV cell.