Conjugation-length dependence of spin-dependent exciton formation rates in pi-conjugated oligomers and polymers.
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.
Wohlgenannt
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M
Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA.
Jiang
X M
XM
Vardeny
Z V
ZV
Janssen
R A J
RA