Abstract
A new photocrosslinkable hole-transporting homopolymer (PX2Cz) was successfully synthesized using 9-((3-methyloxetan-3-yl)methyl)-9′-(4-vinylbenzyl)-9H,9′H-3,3′-bicarbazole monomer via radical polymerization. Biscarbazole, as a hole-transporting material, has two reactive sites that can introduce a radical polymerizable styrene moiety and a photocrosslinkable oxetane moiety. The photocuring temperature and time for the PX2Cz film was optimized to be 120 °C and 10 s. The photocured films showed good solvent resistance, which is favorable for the deposition of an emitting-layer solution on them. In particular, the highest occupied molecular orbital (HOMO) energy of the as-cast PX2Cz film was determined to be-5.37 eV which remained unchanged even after photocuring, thus facilitating hole transportation from the hole-injection layer. Subsequently, solution-processed, green, thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs) were manufactured using PX2Cz as the hole-transport material. The devices displayed a notable performance with an exceptionally low turn-on voltage (Von) of only 2.8 V and a high external quantum efficiency (EQE) of 22.5%; these values are substantially better than those of commonly used poly(9-vinylcarbazole) (PVK)-based OLEDs (Von = 3.6 V, EQE of 15.5%). The remarkably low turn-on voltage and high EQE were ascribed to the shallower HOMO energy level and more pronounced hole-transport ability of the photocured PX2Cz film.
Original language | English |
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Pages (from-to) | 4572-4579 |
Number of pages | 8 |
Journal | Journal of Materials Chemistry C |
Volume | 8 |
Issue number | 13 |
DOIs | |
Publication status | Published - 2020 Apr 7 |
Bibliographical note
Funding Information:This research was supported by LT Materials (Q1829031, 2019). It was also supported by the National Research Foundation of Korea (NRF2019R1A2C2002647, NRF2019R1A6A1A11044070). The authors also thanks to the Korea Basic Science Institute in Seoul for allowing us to use MALDI-TOF MS instrument.
Publisher Copyright:
© The Royal Society of Chemistry.
ASJC Scopus subject areas
- General Chemistry
- Materials Chemistry