Issue 9, 2022

Solution-processable phenothiazine and phenoxazine substituted fluorene cored nanotextured hole transporting materials for achieving high-efficiency OLEDs

Abstract

Solution-processable hole-transporting materials (HTMs) are key functional materials for high-throughput and inexpensive fabrication of high-efficiency organic light-emitting diodes (OLEDs). Herein, we have successfully synthesized a novel series of phenothiazine and phenoxazine substituted fluorene core-based HTMs, i.e. 10-hexyl-3-[2,7-di(naphthalen-1-yl)-fluoren-9-ylmethylene]phenoxazine DNFPhe, 10-hexyl-3-[2,7-di(4-(diphenylamino)-phenyl)fluoren-9-ylmethylene]phenoxazine DDPFPhe, 10-hexyl-3-[2,7-di(4-fluorophenyl)-fluoren-9-ylmethylene]phenoxazine DFPFPhe, 10-hexyl-3-(2,7-diphenylfluoren-9-ylmethylene)phenoxazine DPFPhe, 10-hexyl-3-[2,7-di(4-(diphenylamino)phenyl)fluoren-9-ylmethylene]phenothiazine DDPPFPh, and 10-hexyl-3-[2,7-di(naphthalen-1-yl)fluoren-9-ylmethylene]phenothiazine DNFPh, and incorporated them in solution-processed phosphorescent and thermally activated delayed fluorescence (TADF) OLEDs. The synthesized HTMs exhibit superior solubility in organic solvents and display nanotextured surface morphologies. These HTMs possess high hole-mobilities as compared to a conventional HTM, N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB). By incorporating a phosphorescent bis(4-phenylthieno[3,2-c]pyridinato-N,C2′) (acetylacetonate) iridium(III) (PO-01) yellow emitter, we demonstrate an improvement in maximum power efficacy (PEmax) from 41.6 to 45.4 lm W−1, current efficacy from 39.8 to 50.6 cd A−1, external-quantum efficiency (EQEmax) from 12.9 to 19.6%, maximum brightness (Lmax) from 15 200 to 19 400 cd m−2, and a lifetime (LT50) from 151 to 465 h at 1000 cd m−2 initial luminance of a phosphorescent OLED by substituting the conventional HTM, NPB, with DDPPFPh. Additionally, the 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) green TADF emitter-based OLED displays the enhancement in PEmax from 42.5 to 69.1 lm W−1, CEmax from 54.1 to 78.0 cd A−1, EQEmax from 20.1 to 27.2%, Lmax from 12 900 to 44 200 cd m−2 and LT50 from 195 to 590 h at an initial brightness of 1000 cd m−2 by replacing NPB with DDPPFPh. Based on these findings, the reported solution-processable HTMs appear to be promising candidates for high-efficiency OLEDs.

Graphical abstract: Solution-processable phenothiazine and phenoxazine substituted fluorene cored nanotextured hole transporting materials for achieving high-efficiency OLEDs

Supplementary files

Article information

Article type
Paper
Submitted
02 Nov. 2021
Accepted
30 Janv. 2022
First published
11 Febr. 2022

J. Mater. Chem. C, 2022,10, 3593-3608

Solution-processable phenothiazine and phenoxazine substituted fluorene cored nanotextured hole transporting materials for achieving high-efficiency OLEDs

M. R. Nagar, A. Choudhury, D. Tavgeniene, R. Beresneviciute, D. Blazevicius, V. Jankauskas, K. Kumar, S. Banik, S. Ghosh, S. Grigalevicius and J. Jou, J. Mater. Chem. C, 2022, 10, 3593 DOI: 10.1039/D1TC05237C

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