Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Photon Upconversion Based on Inter-Molecular Energy Transfer in Ionic Liquids: A Technology for Utilizing Sub-Bandgap Wasted Solar Energies

Get access (open in a dialog) DOI: 10.1615/IHTC15.mlt.008514
pages 4999-5009

Abstrakt

Sunlight is one of the most promising renewable energy sources considered for addressing the energy shortage that we may encounter in the future. Presently, most of “solar to secondary energy” conversion systems such as photovoltaics, photocatalysts, and photosyntheses waste significant portion of the solar energy corresponding to the wavelengths longer than a threshold wavelength unique to each system. This is because sub-bandgap photons are wasted by the systems since the energies of such photons are insufficient to induce photo-excitation or photoreaction. This paper pertains to the photo-conversion technology called “photon upconversion (UC)”, which converts longer wavelength light (lower energy photons) into shorter wavelength light (higher energy photons), and hence can circumvent the wasting of the solar energy to improve the overall efficiencies of the solar-energy conversion systems. This paper presents the UC carried out in “ionic liquids”, by utilizing inter-molecular energy transfers between spin-triplet excited states of organic molecules. Recently, we have succeeded in the use of ionic liquids, which are novel room-temperature molten salts having non-flammability and non-volatility, as the media for the energy-carrying organic molecules for the first time. In this paper, we inspect in detail the inter-molecular energy transfer characteristics in a typical ionic liquid usable for this purpose, [C6mim][NTf2]. Furthermore, we developed a prototype UC device based on the developed technology as a basic design consideration to the application, and the details including the applicability to sunlight are presented.