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Title

Controlling singlet–triplet splitting in carbazole–oxadiazole based bipolar phosphorescent host materials

Authors
Kautny, Paul
Wu, Zhongbin
Stöger, Berthold
Horkel, Ernst
Chen, Jiangshan
Ma, Dongge
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Published in Organic Electronics. 2015, vol. 17, p. 216-228
Abstract A rational molecular design strategy for carbazole–oxadiazole based bipolar host materials was developed to improve the device efficiency of blue phosphorescent organic light-emitting diodes (PHOLED). Steric effects of strategically placed methyl groups led to an increase of triplet energies (o-2MPCzPOXD: 2.66 eV and o-3MPCzPOXD: 2.73 eV versus the initial host material o-PczPOXD: 2.62 eV) while less pronouncedly affecting singlet energies and, therefore, retaining low driving voltages, high power efficiencies and remarkably low efficiency roll-offs in PHOLEDs. The maximum quantum efficiencies (EQE) for blue devices (FIrpic) were significantly raised for o-2MPCzPOXD (13.6%) and o-3MPCzPOXD (11.5%) versus o-PCzPOXD (9.0%) although yielding comparable values for green devices (Ir(ppy)3; 12.9% and 15.4% versus 13.2%). Supported by theoretical calculations a structure–property relationship was established from photo-physical properties, PHOLED performance measurements and structural characterization from single crystal data.
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KAUTNY, Paul et al. Controlling singlet–triplet splitting in carbazole–oxadiazole based bipolar phosphorescent host materials. In: Organic Electronics, 2015, vol. 17, p. 216-228. https://archive-ouverte.unige.ch/unige:44949

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Deposited on : 2015-01-12

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