Abstract
The nature of low energy optical excitations, or excitons, in organic solids is of central relevance to many optoelectronic applications, including solar energy conversion. Excitons in solid pentacene, a prototypical organic semiconductor, have been the subject of many experimental and theoretical studies, with differing conclusions as to the degree of their charge-transfer character. Using first-principles calculations based on density functional theory and many-body perturbation theory, we compute the average electron-hole distance and quantify the degree of charge-transfer character within optical excitations in solid-state pentacene. We show that several low-energy singlet excitations are characterized by a weak overlap between electron and hole and an average electron-hole distance greater than 6 Å. Additionally, we show that the character of the lowest-lying singlet and triplet excitons is well-described with a simple analytic envelope function of the electron-hole distance.
Original language | English (US) |
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Pages (from-to) | 2197-2201 |
Number of pages | 5 |
Journal | Journal of Physical Chemistry Letters |
Volume | 4 |
Issue number | 13 |
DOIs | |
State | Published - Jul 3 2013 |
Keywords
- charge-transfer exciton
- electron-hole distribution
- exciton wave function
- many-body perturbation theory
- organic crystals
- organic photovoltaics
- pentacene
ASJC Scopus subject areas
- General Materials Science
- Physical and Theoretical Chemistry