Luminescent Solar Concentrators

Abstract

This chapter reviews recent work by the Quantum Photovoltaic Group (QPV) at Imperial College London and their collaborators in the application of nanostructures to efficiently harvest light within the luminescent solar concentrator (LSC). In addition, the work of other groups and their means for optimizing the efficiency of the LSC are reviewed, as it is most likely that a combination of approaches will lead to the increases in system efficiency required for the commercialization of the LSC. Concentrating light with relatively inexpensive devices onto photovoltaic (PV) cells is a promising route to reducing the cost of PV energy generation and may be achieved using LSCs, which were first proposed about thirty years ago. A LSC (see Figure 9.1) generally consists of a transparent plate or slab doped with luminescent centers. Incident light is absorbed by the luminescent centers and reemitted approximately isotropically, ideally with high luminescence quantum efficiency (LQE). While some of the emission is lost through the escape cones, a large fraction of the emission is trapped within the plate by total internal reflection (TIR) and wave guided to the concentrator edges, where it can be converted by PV cells. Concentration is achieved due to the geometrical ratio between the large surface area and the small edge areas. The LSC also converts the broad incident spectrum into a narrow emission spectrum that can be matched to the band gap of the PV cell such that the cell is operating at optimal efficiency and thermalization occurs in the LSC rather than in the more expensive cell, where the heat would reduce cell efficiency.