Luminescent solar concentrators (LSC) are an attractive emerging concept for semi-transparent, building-integrated photovoltaics at low cost and weight. Hereby, large-area, luminescent wave-guide foils collect solar radiation, being harvested at the wave-guide’s edge by a small-size solar module. To further improve the performance of LSCs, emitter materials with photoluminescence quantum yields (PLQY) near-unity are required, as this minimizes losses due to photon re-absorption events. This presentation show-cases a highly sensitive approach to experimentally determine the PLQY of emitters, combining spectroscopic and photothermal techniques. Screening the PLQY of six emitter molecules in solution, we are able to measure a maximum value of 99.4% with an unprecedented precision down to ±0.3% – which is about ten times better than established techniques. This newly developed method will therefore contribute to the development of future highly efficient LSCs, which require emitters with extremely high PLQYs, well above 99%. We further show that such emitters can perform thermally assisted photon upconversion, illustrating their potential for optical refrigeration.
|