Bipolar material with spiro-fluorenyl terminals: synthesis, characterization and application for enhancement of electrophosphorescence

Abstract

We have designed a novel bipolar material (FTzCz) consisting of spiro-fluorenyl terminals and a bipolar core to enhance emission efficiency of phosphorescent light-emitting diodes based on a conventional poly(9-vinylcarbazole) host and Ir(ppy) 3 dopant. The core is composed of directly linked hole-transporting carbazolyl and electron-affinitive aromatic 1,2,4-triazolyl groups. The bipolar FTzCz was synthesized by the Suzuki coupling reaction and was well characterized. It exhibited not only good thermal stability due to its rigid and non-planar chemical structure, but also facilitated hole-and electron-affinities simultaneously. Blending the bipolar FTzCz with PVK significantly enhanced the performance of electrophosphorescent devices [ITO|PEDOT:PSS|(PVK + FTzCz):Ir(ppy) 3 (4 wt%)| BCP (10 nm)|Ca (50 nm)|Al (100 nm)]. The maximum luminance and maximum luminance efficiency were enhanced from 3550 cd m À2 and 5.6 cd A À1 (neat PVK-based device) to 4510 cd m À2 and 9.9 cd A À1 (blend device with PVK : FTzCz ¼ 8 : 2), respectively. Our results demonstrate the efficacy of the bipolar FTzCz in enhancing performance of electrophosphorescent devices.

Functionalization of phosphorescent emitters and their host materials by main-group elements for phosphorescent organic light-emitting devices

“…[205][206][207][208] With different linking modes, carbazole/ triazole hybrids can realize high E T in the range of 2.8 to 3.0 eV, and CzTAZ (Fig. [205][206][207][208] With different linking modes, carbazole/ triazole hybrids can realize high E T in the range of 2.8 to 3.0 eV, and CzTAZ (Fig.…”

Solution processable double layer organic light emitting diodes (OLEDs) based on 6-N,N-arylsubstituted-1H-pyrazolo[3,4-b]quinolines

“…Compound was prepared according to literature procedure 37 4-(9-Carbazolyl)aniline 5c (1 mol-%, 2.9 mg), sodium tert-butoxide (2 mmol, 200 mg) and toluene (5 mL) were loaded into the tube and flushed with argon. The tube was immersed into a preheated oil bath (100uC) for 24 h. After completion of a reaction as judged by TLC analysis, the reaction mixture was diluted with EtOAc and filtered.…”

Hole‐buffer polymer composed of alternating p‐terphenyl and tetraethylene glycol ether moieties: Synthesis and application in polymer light‐emitting diodes

“…Therefore, balance in carrier injection and transport is a crucial requirement for highly efficient PLEDs. Several strategies have been constantly adopted to enhance carrier balance in light‐emitting diodes, including introduction of low work function cathode, insertion of appropriate carrier‐injection and/or carrier‐transport layer, and by using hole‐blocking layer between emitting layer and cathode . These strategies mostly intend to increase charge injection/transport or to block holes and excitons within emitting layer.…”

“…Several strategies have been constantly adopted to enhance carrier balance in light-emitting diodes, including introduction of low work function cathode, 8 insertion of appropriate carrier-injection and/or carrier-transport layer, [9][10][11][12] and by using hole-blocking layer between emitting layer and cathode. 13,14 These strategies mostly intend to increase charge injection/transport or to block holes and excitons within emitting layer. In this work, we use another approach to improve carrier balance, that is, insert a hole-buffer layer between anode and emitting layer to reduce hole transport.…”

“…The well-known hole-blocking materials, such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and 2,2 0 ,2 00 -(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), usually possess low HOMO levels to obstruct the holes when used as hole-blocking layer. 13,14 Chen et al found that the effect of hole-buffer layer outperforms hole-blocking layer, although they both show promotion in device efficiency. 14 This is because the insertion of hole-buffer layer results in wider recombination region within emission layer, when compared to hole-blocking layer.…”