Recombination of two triplet excitons in conjugated polymers
College of Physics, and Hebei Advanced Thin Films Laboratory,
Hebei Normal University, Shijiazhuang
2 Department of Physics, Xingtai University, Xingtai, 054001, P.R. China
3 Zhangjiakou Vocational and Technical College, Zhangjiakou 075051, P.R. China
Received in final form: 21 October 2012
Published online: 24 December 2012
Combining the one-dimensional tight-binding Su-Schrieffer-Heeger (SSH) model including interchain interactions and the extended Hubbard model (EHM), we investigate the recombination processes between two triplet excitons in conjugated polymers using a nonadiabatic evolution method. Due to the interchain coupling, the electron and/or hole in the two triplet excitons can exchange, and new species are formed. Depending on the interchain coupling and electron-electron interactions, it is found that the main product is excited-polaron state in which two electrons and a hole (or two holes and an electron) are bound together in a lattice deformation, with a small amount of singlet exciton, biexciton and bipolaron. In these products, the excited polaron, the singlet exciton and the biexciton can contribute to the emission. The results indicate that the recombination of two triplet excitons may play an important role in polymer light-emitting diodes.
Key words: Topical issue: Excitonic Processes in Condensed Matter, Nanostructured and Molecular Materials.
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2012