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

Abstract

a b s t r a c tLuminescent 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.

Luminescent Solar Concentrators: The route to 10% efficiency

“…Even in an idealized LSC with only escape cone losses, the trapping probability for every emitted photon is P trap = 1 -P cone = 0.75. Consequently, for a given input energy flux Φ in the output flux Φ out decreases after an average of N−1 reabsorptions per photon to [4]:…”

“…Self-absorption occurs when there is a finite probability for a luminescent species to absorb the light emitted by the same species. This is visualized in an overlap between the spectra of absorption A(λ) and emission F(λ), quantified as self-absorption cross section σ SA per 1 cm optical path [4]:…”

“…Measurements of self-absorption effects for some dyes and nanocrystals were conducted with a position-adjustable excitation source that illuminates different spots in the 978-1-4799-4398-2/14/$31.00 ©2014 IEEE material so that the optical path length travelled by the emitted light inside the luminescent solution can be varied [4]. The self-absorption crosssection of Rhodamine 6G (LQE=95%) and Lumogen Orange (LQE=95%) were calculated to be 8.5% and 6.7%, respectively.…”

The “Electric Mondrian” as a Luminescent Solar Concentrator Demonstrator Case Study

“…New nanocrystal-based luminophores are under development that allow for larger sizes at high device efficiencies. [10][11][12][13][14][15] Most of LSC applications are in the phase of research, testing, or validation. At the moment, LSC devices are tested to replace sound barriers in Den Bosch, the Netherlands [16] or be used as roof tiles, [17] and, interestingly, as miniature chemical reactors.…”

Will luminescent solar concentrators surpass the 10% device efficiency limit?

“…Another part is guided to the solar cell by total internal reflection. 4 as low as possible. Third, near-unity luminescence quantum efficiency (LQE) is required.…”