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Research

Luminescent Solar Energy Concentrators

Principal investigator: Cees BASTIAANSEN
Co-investigator(s): and M. Debeje

Schematic of a Luminescent Solar Energy Concentrators (LSC).Attaining higher conversion efficiencies at lower costs is the key driver in photovoltaics (PV) research and development and has been so for many decades. Today, the prices of PV modules are too high and widespread deployment of PV technology still needs financial support schemes, such as investment subsidies or feed-in tariffs, the latter being also a quality assurance check. Nevertheless, over the past 10 years the PV industry is experiencing average annual growth rates of 40%. To reach lower cost per installed capacity (£/W), several routes are being pursued, all more or less directed towards a better use of the complete solar spectrum, and they are being referred to as Next or Third Generation PV. Conversion of the incident solar spectrum to monochromatic light would greatly increase the efficiency of solar cells.

Luminescent solar concentrators (LSC) are being developed as an alternative approach to lower the costs of PV. The basic design of a luminescent solar concentrator (LSC) allows sunlight to penetrate the top surface of an inexpensive plastic waveguide. The light is absorbed by embedded dye molecules and re-emitted at a longer wavelength. A fraction of the re-emitted light is trapped in the waveguide by total internal reflection and becomes concentrated along the edges. A small-area, high-efficiency PV cell is placed at one (or more) edges of the waveguide to collect the concentrated light and to convert it to electricity. A prime advantage of the LSC over a silicon PV panel is that much smaller solar cells are needed (the PV area is reduced by at least 90%). The system cost and the cost per unit energy is reduced by minimizing the area of the expensive material (the PV cell) and maximizing the area of the inexpensive plastic solar collector. Some advantages of LSC over standard solar concentrators based on geometrical optics are that LSCs allow more efficient collection of diffuse (indirect) sunlight (no tracking of the sun is necessary), they can be flat, made into a variety of shapes, can have different colours, and can be made translucent. LSCs are therefore of special interest for building integrated PV applications.