Tackling self-absorption in luminescent solar concentrators with type-II colloidal quantum dots

Luminescent solar concentrators are low cost photovoltaic devices, which reduce the amount of necessary semiconductor material per unit area of a solar collector by means of concentration. The device is comprised a thin plastic plate in which luminescent species (fluorophores) have been incorporated. The fluorophores absorb the solar light and radiatively re-emit part of the energy. Total internal reflection traps most of the emitted light inside the plate and wave-guides it to a narrow side facet with a solar cell attached, where conversion into electricity occurs. The efficiency of such devices is as yet rather low, due to several loss mechanisms, of which self-absorption is of high importance. This work demonstrates that type-II semiconductor hetero-nanocrystals may offer a solution to the self-absorption problem in luminescent solar concentrators.