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1 December 1997 Variational studies on charge transfer in a molecularly doped polymer
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The photoinduced charge transfer between a conjugated polymer chain and an adjacent dopant molecule is studied by constructing a variational wavefunction for the whole system including the chain and dopant. The dopant is modeled by assuming it has an acceptor level for the electron and interacts with the polymer chain only via a nearest neighbor hopping. The initial exciton state in the polymer is calculated from a recently developed exciton theory for conjugated polymers. The variational wavefunction contains two terms: the first term describes the exciton as confined to the chain while the other describes the electron, with different electron momenta corresponding to different probability of transfer to the dopant. Minimizing the energy of the variational state we obtain an equation from which the energy of the variation state and associated probability of charge transfer can be calculated. It is shown that a crossover occurs when the acceptor level approaches the exciton energy. When the energy of the acceptor level is higher than a critical value, the electron mainly remains on the chain, otherwise the electron will transfer to the dopant molecule with high probability. The hopping strength and the dopant concentration influence charge transfer by controlling the width of the crossover energy regime. Our results also indicate that the symmetry of the exciton wavefunction is important to charge transfer. For the Ag exciton, there exists a threshold for the acceptor level, below this value the electron will transfer to the dopant completely. In contrast, for the Bu exciton there is a long tail below the critical value, implying that the electron can still be found on the polymer chain with some likelihood.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Zhi Gang Yu, Avadh B. Saxena, and Alan R. Bishop "Variational studies on charge transfer in a molecularly doped polymer", Proc. SPIE 3145, Optical Probes of Conjugated Polymers, (1 December 1997);

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