Multiphonon emission model of spin-dependent exciton formation in organic semiconductors

Abstract

The maximum efficiency in organic light-emitting diodes (OLEDs) depends on the ratio, $r=k_S/k_T$, where $k_S$ ($k_T$) is the singlet (triplet) exciton formation rate. Several recent experiments found that r increases with increasing oligomer length from a value $r\approx 1$ in monomers and short oligomers. Here, we model exciton formation as a multi-phonon emission process. Our model is based on two assertions: (i) More phonons are emitted in triplet formation than in singlet formation. (ii) The Huang-Rhys parameter for this phonon emission is smaller in long oligomers than in short ones. We justify these assertions based on recent experimental and theoretical data.

arXiv comment8 pages, 7 figures

References in corpus (5)

• Conjugation-Length Dependence of Spin-Dependent Exciton Formation Rates in Pi-Conjugated Oligomers and Polymers
• Spin-dependent electron-hole capture kinetics in conjugated polymers
• Electron correlation effects in electron-hole recombination in organic light-emitting diodes
• Theory of the singlet exciton yield in light-emitting polymers
• Excited states of linear polyenes

Cited by in corpus (2)

• Hyperfine interaction and magnetoresistance in organic semiconductors
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