Singlet Exciton Fission based Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) comprise a transparent plastic film doped with luminophores that absorb and remit light. The light is then wave-guided within the film, thus concentrating it, and is finally absorbed by PVs attached at the ends. Theoretically, a LSC can outperform any optical concentration scheme due to its ability to concentrate diffuse light, something entropically forbidden for an optical concentrator. Nor does a LCS does require any solar tracking, as an optical concentrator does. Thus LCSs holds the promise of greatly reducing the cost of solar energy, as the low-cost, light-weight LSC could greatly reduce the use of PV panels, saving both the cost of the PV and lowering the balance of systems cost.

In practice, LSCs have failed to meet their promise due to high reabsorption losses, due to small Stokes shifts between luminophore absorption and emission. This project will take a radical new approach to LSCs combining highly efficient quantum dot emitters with the process of singlet exciton fission, a carrier multiplication process in organic semiconductors which allows for the generation of two electron-hole pairs for each photon absorbed. Each of these electron-hole pairs, bound together as a quasi particle known as an exciton, lie at half the bandgap of the organic semiconductor. By transferring their energy to the quantum dots, which then emit a photon, we can turn high a energy photon in to two low-energy photons, eliminating both re-absorption and thermalisation losses. This should allow us to achieve concentration factors of up to 200, against the current best of 30, and pave the way for a new generation of LSC that could radically lower the cost of solar energy.

The project will involve a range of experimental and modelling activities, including LSC fabrication, steady state and time-resolved (ps-fs) optical spectroscopy and optical modelling.

Tomi Baikie

Cohort 4