| Автор | Kikuo Harigaya |
| Дата выпуска | 1997-06-16 |
| dc.description | The component of photoexcited states with large spatial extent in the optical absorption spectra of the electroluminescent polymer poly( para-phenylenevinylene) (PPV) is investigated by using the intermediate-exciton theory. We find that there is a peak due to long-range excitons on the higher-energy side of the lowest main feature of the optical spectra. The energy position is nearly the same as that of the Hartree - Fock (HF) energy gap. The oscillator strengths of long-range excitons are larger when the electric field of the light is perpendicular to the chain axis. The fact that the onset of the long-range excitons is located near the HF gap might be related to the mechanisms of the large photocurrents measured in this energy region. Next, we calculate the ratio of the oscillator strengths due to long-range excitons to the sum of all of the oscillator strengths of the absorption, as a function of the PPV monomer number. The ratio depends strongly on the system size when the monomer number is low, but the magnitude of the ratio becomes almost constant when the monomer number is more than 10 and near 20, even though slight boundary condition effects persist. Finally, we discuss two different theoretical assignments of the characters of the main features in the absorption of PPV. We show that a large value of the hopping integral is realistic for optical excitations in the neutral PPV chain. The experimental feature at around 5.8 eV is mainly due to localized excitons. |
| Формат | application.pdf |
| Издатель | Institute of Physics Publishing |
| Название | Excitons in the optical absorption spectra of the electroluminescent polymer poly( para-phenylenevinylene) |
| Тип | paper |
| DOI | 10.1088/0953-8984/9/24/021 |
| Electronic ISSN | 1361-648X |
| Print ISSN | 0953-8984 |
| Журнал | Journal of Physics: Condensed Matter |
| Том | 9 |
| Первая страница | 5253 |
| Последняя страница | 5263 |
| Аффилиация | Kikuo Harigaya; Physical Science Division, Electrotechnical Laboratory, Umezono 1-1-4, Tsukuba, Ibaraki 305, Japan |
| Выпуск | 24 |
