Electron affinity and binding energy of excitons in disordered organic semiconductors. III. Multimethod study for films of the blue fluorescent emitter MADN

A method is developed for deducing the electron affinity of disordered organic semiconductors from spectroscopic thin-film studies of the ionization energy and the optical gap energy, combined with field-induced dissociation (FID) device experiments that are analyzed with kinetic Monte Carlo simulations using a methodology that has been presented by de Jong , . The FID experiments are carried out for a set of eight organic semiconductor materials that are often used in organic light-emitting diodes. The analysis is focused on the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>α</a:mi> </a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mi>β</b:mi> </b:math> isomers of the blue fluorescent emitter material 2-methyl-9,10-di-naphthyl-anthracene. For these two materials, the experimental ionization energy, the optical gap energy, the exciton binding energy, and the electron affinity are shown to be consistent with the results of quantum-chemical calculations, presented by G. Tirimbò , . For all fluorescent emitter materials studied, the FID experiments reveal an exciton binding energy of approximately 1.0–1.2 eV, whereas for a thermally activated delayed fluorescence material, a slightly smaller value is obtained.