Charge Transfer Dynamics in Donor鈥揂cceptor Complexes between a Conjugated Polymer and Fluorene Acceptors

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• 作者：Vlad G. Pavelyev ; Olga D. Parashchuk ; Michal Krompiec ; Tatyana V. Orekhova ; Igor F. Perepichka ; Paul H. M. van Loosdrecht ; Dmitry Yu. Paraschuk ; Maxim S. Pshenichnikov
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：December 26, 2014
• 年：2014
• 卷：118
• 期：51
• 页码：30291-30301
• 全文大小：552K
• ISSN：1932-7455

文摘

We report on ground and excited state charge transfer in charge-transfer complexes in films formed between a semiconducting polymer, MEH-PPV (poly[2-methoxy-5-(2鈥?ethylhexyloxy)-1,4-phenylenevinylene]), and a series of fluorene electron acceptors. The latter were designed to vary systematically the electron affinity (EA) over 鈭?.5 eV by attachment of various electron withdrawing groups to the fluorene core. The EAs of the acceptors are determined by cyclic voltammetry and compared with those from density functional theory calculations. The charge-transfer dynamics are studied using an ultrafast visible-pump鈥揑R-probe photoinduced absorption technique. We demonstrate that the acceptor EA is the key鈥攂ut not the only鈥攑arameter that governs charge recombination rates that scale exponentially with the acceptor EA. From the time-resolved data we deduced a model that describes charge dynamics for acceptors with low and high EAs. The two opposite trends鈥攈igher acceptor EA increases the driving force for charge separation but also inevitably increases the rate of undesirable charge recombination鈥攕hould be carefully counterbalanced in designing novel polymer鈥揻ullerene bulk heterojunctions.