5,10-Dihydrobenzo[a]indolo[2,3‑c]carbazoles as Novel OLED Emitters

• Published in: The journal of physical chemistry. B Vol. 123; no. 6; pp. 1400 - 1411
• Main Authors: de Jong, Flip, Daniels, Mathias, Vega-Castillo, Luis, Kennes, Koen, Martín, Cristina, de Miguel, Gustavo, Cano, Manuel, Pérez-Morales, Marta, Hofkens, Johan, Dehaen, Wim, Van der Auweraer, Mark
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.02.2019
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.8b10942

The excited-state dynamics of four 5,10-dihydrobenzo­[a]­indolo­[2,3-c]­carbazoles in solution and in films were studied with stationary and time-resolved spectroscopies. The solvent dependency of the photophysics reveals no appreciable dipole moment in the ground state. In the excited state, electron-withdrawing substituents contribute to an outspoken charge-transfer character. In films, although the molecules are mostly present as monomers, the excited-state dynamics are characterized by a cascade of energy-transfer processes to excited dimers and aggregates which dominate the photoluminescence (PL) spectra. The properties of the aggregates depend on the used substituents. The electroluminescence spectra obtained from single-layer and multilayer devices mostly resemble the PL spectra, but show contributions from other species such as electromers or electroplexes. It is inferred that the different substituents lead to a different packing of the carbazole moieties, each of which has different mobilities and recombination probabilities.