Solution processed blue-emitting and hole-transporting materials from truxene-carbazole-pyrene triads
Chomchanok Wongsilarat, Supawadee Namuangruk, Narid Prachumrak, Taweesak Sudyoadsuk, Vinich Promarak, Mongkol Sukwattanasinitt, Paitoon Rashatasakhon
Index: 10.1016/j.orgel.2018.03.035
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Abstract
A new series of truxene derivatives containing different numbers of dipyrenylcarbazole substituents are prepared and evaluated as emissive and hole-transporting layers in electroluminescent devices. The compounds are synthesized from Cu-catalyzed C-N coupling between the iodotruxene core and 3,6-dipyrenylcarbazole and characterized by 1H NMR, 13C NMR and MALDI-TOF mass spectroscopy. These compounds exhibit strong fluorescence in the blue region and show excellent thermal stabilities with Td10% above 440 °C. They are tested as non-doped blue emitters in the OLEDs with the structure of ITO/PEDOT:PSS/EML/BCP/LiF:Al. The derivative containing two dipyrenylcarbazole moieties exhibits the highest maximum brightness of 8.0 × 103 cd/m2 at 9.6 V with a low turn-on voltage (Von) of 3.4 V. In the devices of structure ITO/PEDOT:PSS/HTL/Alq3/LiF:Al, the compound also shows superior hole-transporting properties in comparison with the standard compound (N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine). The device fabricated from this compound as the HTL shows the highest maximum brightness of 4.5 × 104 cd/m2 at 10.8 V with a low turn-on voltage (Von) of only 2.8 V.