Phosphine-Oxide-Containing Bipolar Host Material for Blue Electrophosphorescent Devices

Abstract

We report highly efficient blue electrophosphorescent organic light-emitting diodes (OLEDs) incorporating a bipolar host, 2,7-bis(diphenylphosphine oxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF), doped with iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C 2′ ]picolinate (FIrpic). PCF, which contains diphenylphosphine oxide groups appended onto a carbazole/fluorene hybrid, displays both electron- and hole-transporting characteristics, resulting in a low turn-on voltage (2.6 V) and greatly improved power efficiencies. In addition, the sterically hindered structure of PCF provides a compatible environment for the FIrpic dopant, alleviating concentration quenching of the phosphor at high doping levels. The device doped with 28 wt % FIrpic exhibited maximum EL efficiencies of 30.8 cd/A and 26.2 lm/W (at 121 cd/m2). Even at a high brightness of 1000 cd/m2, the efficiencies remained high (26.9 cd/A and 19.6 lm/W).

Highly Emitting Neutral Dinuclear Rhenium Complexes as Phosphorescent Dopants for Electroluminescent Devices

“…Vacuum-deposited devices: The host molecule 2,7-bis(diphenylphosphine oxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF) was prepared using previously reported procedures [31]. The hole-transport material 4,4 0 -bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), the holeblocker 2,9-dimethy-4,7-diphenyl-1,10-phenanthroline (BCP), and the electron-transport material tris(8-hydroxyquinolinate) aluminum (Alq 3 ) were all purchased from LumTec Corp. and used without further purification.…”

“…NPB and Alq 3 were utilized as hole-and electrontransport layers, respectively; BCP was employed as a simultaneous electron-transport and hole-block layer. Bipolar host material PCF [31] , which features diphenylphosphine oxide groups appended to a carbazole/fluorene hybrid, was used as the host material for the rhenium complex. Figure 7 shows the corresponding EL spectrum at a bias of 7 V, with the CIE color coordinates of 0.26, 0.54 representing a green-yellow emission.…”

A Highly Efficient Universal Bipolar Host for Blue, Green, and Red Phosphorescent OLEDs

“…[2] However, a drawback is that the introduction of an electron-donating and -withdrawing moiety to the host molecule would lead to an intramolecular charge transfer resulting in the reduction of energy gap of the molecule. Several bipolar hosts for sky-blue phosphorescent devices were synthesized including a pyridine/ carbazole hybrid, 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine (26DCzPPy) by Kido et al, [3] a phosphine oxide/carbazole hybrid, N-(4-diphenylphosphoryl phenyl) carbazole (MPO12) by Sapochak and his coworkers and phosphine oxide/phenylamine bipolar materials, [4,5] 2,7-bis(diphenylphosphineoxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF) and 2,7-bis(diphenylphosphoryl)-9-[4-(N,N-diphenylamino) phenyl]-9-phenylfluorene (POAPF) by Shu and Chou et al [6,7] . Bipolar hosts for green phosphorescent devices were also known.…”

A Novel, Bipolar Polymeric Host for Highly Efficient Blue Electrophosphorescence: a Non‐Conjugated Poly(aryl ether) Containing Triphenylphosphine Oxide Units in the Electron‐Transporting Main Chain and Carbazole Units in Hole‐Transporting Side Chains

“…[17][18][19][20][21][22][23][24] For example, by chemical bonding of both p-and n-type groups into its molecular structure, Cheng et al [ 17 ] developed a bipolar molecular host with an E T of 3.01 eV, and a blue-light-emitting device with an effi ciency of 45.1 cd A − 1 (40.6 lm W − 1 ) was obtained when it was doped with iridium(III)[bis(4,6-difl uorophenyl)-pyridinato-N,C 2 ]-picolinate (FIrpic). Despite these great achievements, polymeric hosts adopting this "bipolar" conception have not been explored for blue-emitting PhPLEDs until now.…”