24 August 2010 Molecular approaches to third generation photovoltaics: photochemical up-conversion
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We have investigated a photochemical up-conversion system comprising a molecular mixture of a palladium porphyrin to harvest light, and a polycyclic aromatic hydrocarbon to emit light. The energy of harvested photons is stored as molecular triplet states which then annihilate to bring about up-converted fluorescence. The limiting efficiency of such triplet-triplet annihilation up-conversion has been believed to be 11% for some time. However, by rigorously investigating the kinetics of delayed fluorescence following pulsed excitation, we demonstrate instantaneous annihilation efficiencies exceeding 40%, and limiting efficiencies for the current system of ≈60%. We attribute the high efficiencies obtained to the electronic structure of the emitting molecule, which exhibits an exceptionally high T2 molecular state. We utilize the kinetic data obtained to model an up-converting layer irradiated with broadband sunlight, finding that ≈3% efficiencies can be obtained with the current system, with this improving dramatically upon optimization of various parameters.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yuen Yap Cheng, Yuen Yap Cheng, Burkhard Fückel, Burkhard Fückel, Derrick A. Roberts, Derrick A. Roberts, Tony Khoury, Tony Khoury, Raphaël G. C. R. Clady, Raphaël G. C. R. Clady, Murad J. Y. Tayebjee, Murad J. Y. Tayebjee, Roland Piper, Roland Piper, N. J. Ekins-Daukes, N. J. Ekins-Daukes, Maxwell J. Crossley, Maxwell J. Crossley, Timothy W. Schmidt, Timothy W. Schmidt, } "Molecular approaches to third generation photovoltaics: photochemical up-conversion", Proc. SPIE 7772, Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion, 777207 (24 August 2010); doi: 10.1117/12.862739; https://doi.org/10.1117/12.862739


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