Kinetic Analysis of Photochemical Upconversion by Triplet−Triplet Annihilation: Beyond Any Spin Statistical Limit

Upconversion (UC) via triplet−triplet annihilation (TTA) is a promising concept to improve the energy conversion efficiency of solar cells by harvesting photons below the energy threshold. Here, we present a kinetic study of the delayed fluorescence induced by TTA to explore the maximum efficiency of this process. In our model system we find that more than 60% of the triplet molecules that decay by TTA produce emitters in their first excited singlet state, so that the observed TTA effiency exceeds 40% at the point of the highest triplet emitter concentration. This result thoroughly disproves any spin-statistical limitation for the annihilation efficiency and thus has crucial consequences for the applicability of an upconvertor based on TTA, which are discussed.

[1]  Timothy D Heidel,et al.  High-Efficiency Organic Solar Concentrators for Photovoltaics , 2008, Science.

[2]  R. Dabestani,et al.  Role of triplet-triplet annihilation in anthracene dimerization , 1983 .

[3]  Murad J Y Tayebjee,et al.  On the efficiency limit of triplet-triplet annihilation for photochemical upconversion. , 2010, Physical chemistry chemical physics : PCCP.

[4]  R. Weisman,et al.  Determination of Triplet Quantum Yields from Triplet−Triplet Annihilation Fluorescence , 2000 .

[5]  H. Löhmannsröben,et al.  Investigation of Triplet Tetracene and Triplet Rubrene in Solution , 1986 .

[6]  F. Castellano,et al.  Triplet Sensitized Red-to-Blue Photon Upconversion , 2010 .

[7]  Andrei V. Cheprakov,et al.  Upconversion with ultrabroad excitation band: Simultaneous use of two sensitizers , 2007 .

[8]  G. Wegner,et al.  Up-conversion fluorescence: noncoherent excitation by sunlight. , 2006, Physical review letters.

[9]  G. C. Nieman,et al.  Triplet—Triplet Annihilation and Delayed Fluorescence in Molecular Aggregates , 1963 .

[10]  Raymond Ziessel,et al.  Boron dipyrromethene chromophores: next generation triplet acceptors/annihilators for low power upconversion schemes. , 2008, Journal of the American Chemical Society.

[11]  N. Turro,et al.  Advances in photochemistry , 1996 .

[12]  F. Castellano,et al.  Anti-Stokes delayed fluorescence from metal-organic bichromophores. , 2004, Chemical communications.

[13]  F. Castellano,et al.  Low power visible-to-UV upconversion. , 2009, The journal of physical chemistry. A.

[14]  P. Merkel,et al.  The triplet state energies of rubrene and diphenylisobenzofuran , 1981 .

[15]  Timothy W. Schmidt,et al.  A molecular approach to the intermediate band solar cell: The symmetric case , 2008 .

[16]  L. Ilharco,et al.  Kinetics of Triplet−Triplet Annihilation of Tetraphenylporphyrin in Liquid and Frozen Films of Decanol on the External Surface of Zeolite. Fast Probe Diffusion in Monolayers and Polycrystals , 2003 .

[17]  F. Castellano,et al.  Pd(II) phthalocyanine-sensitized triplet-triplet annihilation from rubrene. , 2008, The journal of physical chemistry. A.

[18]  M. Green,et al.  Improving solar cell efficiencies by up-conversion of sub-band-gap light , 2002 .

[19]  D. Reinhoudt,et al.  Single-molecule pump-probe detection resolves ultrafast pathways in individual and coupled quantum systems. , 2005, Physical review letters.

[20]  A. McLean,et al.  Faraday communications. Efficiency of triplet-photosensitised singlet oxygen generation in benzene , 1990 .

[21]  Angelo Monguzzi,et al.  Multicomponent polymeric film for red to green low power sensitized up-conversion. , 2009, The journal of physical chemistry. A.

[22]  G. Wegner,et al.  Efficient upconversion fluorescence in a blue-emitting spirobifluorene-anthracene copolymer doped with low concentrations of Pt(II)octaethylporphyrin. , 2005, The Journal of chemical physics.