Issue 14, 2018

Purely organic materials for extremely simple all-TADF white OLEDs: a new carbazole/oxadiazole hybrid material as a dual-role non-doped light blue emitter and highly efficient orange host

Abstract

White organic light-emitting diodes (WOLEDs) based on thermally activated delayed fluorescence (TADF) emitters are highly attractive owing to TADF materials providing a favorable low-cost alternative approach to realize high-efficiency electroluminescence. In this work, an extremely simple all TADF WOLED with a single-emissive-layer singe-host/dopant system is demonstrated, by the design of a new TADF material as a dual-role non-doped light-blue emitter and efficient host for a yellow TADF dopant. The carbazole/oxadiazole hybrid compound 2-(2,3,4,5,6-penta(9H-carbazol-9-yl)phenyl)-5-phenyl-1,3,4-oxadiazole (5CzOXD) shows bright light-blue TADF emission with a photoluminescence (PL) peak at 496 nm, and a PL quantum yield of 8.6 and 58.2% under ambient conditions and under degassed toluene, respectively. 5CzOXD also exhibits a delayed decay time of 13 μs in a PMMA doped film as well as a narrow singlet–triplet bandgap (ΔEST) of 0.22 eV. A maximum current efficiency (ηc) and external quantum efficiency (ηext) of 19.3 cd A−1 and 9.3% or 12 cd A−1 and 3.6% are achieved in light blue TADF OLEDs by using 5CzOXD as a doped or non-doped emitter, respectively. A moderately high triplet energy level of 2.58 eV guarantees the application of 5CzOXD as an efficient organic host material for green and yellow TADF OLEDs, with maximum ηext as high as 16.2 and 17.1%, respectively. In addition, a two-color WOLED with the extremely simple device architecture of ITO/MoO3 (8 nm)/TAPC (40 nm)/5CzOXD:4CzPNPh (0.6 wt%, 10 nm)/BmPyPB (40 nm)/LiF (1 nm)/Al is subsequently fabricated, which shows maximum ηc and ηext of 21.5 cd A−1 and 7.2%, respectively, with CIE coordinates of (0.35, 0.44). This simple strategy provides a bright future for constructing low-cost efficient vacuum-deposited WOLEDs based on all organic TADF materials for solid state lighting.

Graphical abstract: Purely organic materials for extremely simple all-TADF white OLEDs: a new carbazole/oxadiazole hybrid material as a dual-role non-doped light blue emitter and highly efficient orange host

Supplementary files

Article information

Article type
Paper
Submitted
01 nov 2017
Accepted
21 nov 2017
First published
21 nov 2017

J. Mater. Chem. C, 2018,6, 3675-3682

Purely organic materials for extremely simple all-TADF white OLEDs: a new carbazole/oxadiazole hybrid material as a dual-role non-doped light blue emitter and highly efficient orange host

D. Zhang, X. Cao, Q. Wu, M. Zhang, N. Sun, X. Zhang and Y. Tao, J. Mater. Chem. C, 2018, 6, 3675 DOI: 10.1039/C7TC04969B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements