Planar photonic solar concentrators for building-integrated photovoltaics

Planar photonic concentrators are a promising concept for low-cost building integrated photovoltaic. In this work, they are formed from colloidal photonic crystal layers deposited by the Langmuir-Blodgett technique onto clear polymethylacrylate sheets with a solar cell attached to the edge. Light is scattered into a waveguide mode and guided via total internal reflection to the edge mounted solar cell. Transmission and reflection measurements taken in different geometries strongly indicate an increased scattering of the incident light over a wide range of wavelengths, depending on the size of the beads forming the photonic crystal film. IV measurements on solar cells attached to one side of a sheet with 8 layers of 250 nm beads exhibit a relative increase in efficiency by a factor of up to 3 as compared to the blank PMMA sheet. These concentrators can increase the power output from photovoltaic cells without the need for solar tracking and have the potential of achieving a lifetime matching standard silicon solar cells.