Exciplex Formation in Blended Spin-Cast Films of Fluorene-Linked Dyes and Bisphthalimide Quenchers

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• 作者：David J. Stewart ; Matthew J. Dalton ; Rachel N. Swiger ; Thomas M. Cooper ; Joy E. Haley ; Loon-Seng Tan
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：May 16, 2013
• 年：2013
• 卷：117
• 期：19
• 页码：3909-3917
• 全文大小：440K
• 年卷期：v.117,no.19(May 16, 2013)
• ISSN：1520-5215

文摘

Spin-cast films of dyes (donor鈭捪€鈥揹onor, donor鈭捪€鈥揳cceptor, and acceptor鈭捪€鈥揳cceptor type, where the donor is Ph₂N鈥? the acceptor is 2-benzothiazoyl, and the 蟺-linker is 9,9-diethylfluorene) blended with nonconjugated bisphthalimides were prepared. Upon visible-light excitation of the dyes, quenching of the excited state occurs by exciplex formation between dye and bisphthalimide molecules or, in some cases, by excimer formation or aggregation-induced emission between two dye molecules. The extent of exciplex formation is dependent on the driving force, which can be calculated using the energy difference between the lowest unoccupied molecular orbitals (LUMOs) of the dyes and bisphthalimides. The results show that complete exciplex formation occurs when this driving force is greater than 0.57 eV whereas partial exciplex formation occurs when the driving force is between 0.28 and 0.57 eV. The exciplex emission energies can also be predicted by calculating the difference between the LUMO level of the bisphthalimide and the highest occupied molecular orbital (HOMO) of the dye. These calculated values, which were obtained from the electrochemically determined energy levels, showed good agreement with the observed emission energies. The exciplex lifetimes were found to be significantly longer than the lifetimes of the lone dyes. These exciplexes formed from nonlinked donors and acceptors in the solid state might have potential uses in nonlinear photonics.