LSC’s aim at lowering cost of solar energy generation by concentrating sunlight using a cheap luminescent plate onto small area strip solar cells. Sunlight is absorbed by a luminescent material and re-emitted in all directions. A considerable fraction of the light is trapped in the plate, that acts as a light guide by total internal reflection (like in a fiber optical cable) and guided to the perimeter where solar cells convert it into electric power. The idea dates back a long time but renewed urgency for sustainable energy sources and new materials and idea’s have sparkled worldwide research activities. Our aim is to develop new rare earth and transition metal doped inorganic luminescent materials with broadband UV/VIS absorption and a large Stokes shift. In addition we make luminescent solar concentrators based on new concepts and test their efficiency.

Building Integrated LSC technology

We investigate the possibility to use LSC’s as windows in homes and offices. By giving glass facades of buildings a LSC function we have calculated that several 10’s of watts/m² of power can be generated depending on the color and quality of the LSC as shown to the left. The more sunlight is absorbed the more power can be generated but the more colored the window becomes. The relation between color and efficiency is shown in the graph to the left, together with two other important parameters e.g. window surface area (Width x Hight) and attenuation length μ, a parameter that quantifies light transport efficiency. Currently we are investigating the business case of a high 10% power efficient LSC as a window or facade and compare LSC’s with thin-film solar cell technology.

Recently we have discovered new materials that have significantly improved properties compared to state-of-the-art luminescent materials based on organic dye’s. Our materials absorb twice as much power from the sun as the well-known dye Red305 as shown to the right. In addition they have no self-absorption. These improvements enhance the efficiency by a factor ranging from 4 to 10 depending on the size of the window. This means that a high efficiency LSC PV device called power window, becomes in reach. Contrary to the dyes or nanoparticles used in most prototypes so far, our materials are “simple” cheap inorganic materials doped with low % of rare earth ions. Such inorganic luminescent materials are also succesful in TV-screens, tube-lighting and LED based lighting, and many more applications.  As our materials absorb all visible light, the LSC made from it will have no color so that options for integration in the build environment become wider.