title: Conjugation-length dependence of spin-dependent exciton formation rates in pi-conjugated oligomers and polymers.
abstract: We have measured the ratio, r = sigma(S)/sigma(T) of the formation cross section, sigma of singlet and triplet excitons from polarons in pi-conjugated oligomer and polymer films, using a spectroscopic technique we developed recently. We discovered a universal relation between r and the conjugation length (CL): r(-1) depends linearly on CL-1, irrespective of the chain structure. Since r is directly related to the maximum possible electroluminescence quantum efficiency in organic light emitting diodes (OLED), our results indicate that polymers have an advantage over small molecules in OLED applications.
authors: Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA.
authors: M
authors: M
authors: Wohlgenannt
authors: X M
authors: XM
authors: Jiang
authors: Z V
authors: ZV
authors: Vardeny
authors: R A J
authors: RA
authors: Janssen