Particle physicists have long been familiar with the idea of shifting the wavelength of light to make detection easier – now the same idea could prove a boon for solar power. Michael Currie and colleagues from the Massachusetts Institute of Technology have shown that planar waveguides with a thin film of organic coating on one side and solar cells on the edges can produce significantly more power than the solar cells on their own.
Their “organic solar concentrators” consist of a thin film of organic dye deposited on glass with a high refractive index. The dye absorbs solar radiation and then re-emits it at longer wavelengths, with some 80% of the re-emitted photons being trapped within the glass by total internal reflection. The team constructed concentrators in tandem so that light passing through the first structure could be absorbed by the second. Standard solar cells mounted on the edges of the device collect the wavelength-shifted photons.
The researchers report quantum efficiencies above 50% and suggest that, ultimately, the devices could achieve 10-fold increases in power compared with standard solar cells – and this is achieved without the need for solar tracking.