A Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl‐Substituted Fluorene Units for Highly Efficient Blue Electrophosphorescence

Abstract

Highly efficient blue electrophosphorescent organic light‐emitting diodes incorporating a bipolar host, 2,7‐bis(diphenylphosphoryl)‐9‐[4‐(N,N‐diphenylamino)phenyl]‐9‐phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6‐difluoro‐phenyl)pyridinato‐N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron‐donating (p‐type) triphenylamine group and an electron‐accepting (n‐type) 2,7‐bis(diphenyl‐phosphoryl)fluorene segment linked through the sp3‐hybridized C9 position of the fluorene unit. The lack of conjugation between these p‐ and n‐type groups endows POAPF with a triplet energy gap (ET) of 2.75 eV, which is sufficiently high to confine the triplet excitons on the blue‐emitting guest. In addition, the built‐in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF‐based device doped with 7 wt% FIrpic exhibits a very low turn‐on voltage (2.5 V) and high electroluminescence efficiencies (20.6% and 36.7 lm W−1). Even at the practical brightnesses of 100 and 1000 cd m−2, the efficiencies remain high (20.2%/33.8 lm W−1 and 18.8%/24.3 lm W−1, respectively), making POAPF a promising material for use in low‐power‐consumption devices for next‐generation flat‐panel displays and light sources.

Highly Selective 1,4‐ and 1,6‐Addition of P(O)H Compounds to p‐Quinones: A Divergent Method for the Synthesis of C‐ and O‐Phosphoryl Hydroquinone Derivatives

“…Hydroquinone compounds bearing heteroatom functionalities form a class of valuable compounds with wide applications. [1][2][3][4][5][6][7][8] Many of them serve as important intermediates from which to access molecules with advanced structures by further manipulating the heteroatomic group through synthetic chemistry. [2,3] Some hydroquinones with heteroatom functionalities are used as reagents in medical research, showing a variety of biological activities in aspects related to antitumor, [4] HIV transcriptase inhibition, and immunomodulation.…”

Manipulating efficiencies through modification of N-heterocyclic phenyltriazole ligands for blue iridium(III) complexes

“…3(c) gives the current densityevoltageeluminance characteristics for AeC. They possess a low turn-on voltages (defined as the bias at a brightness of 1 cd m À2 ) of 2.7 V, which is probably inseparable from the facilitation of both hole and electron injection when using bipolar POAPF as the host material [58]. This turn-on voltage represents the relatively low value among the reported blue phosphorescent OLEDs.…”

“…S5. 2,7-bis(diphenylphosphoryl)-9-(4-diphenylamino)phenyl-9 0 -phenyl-fluorene (POAPF) is selected as the optimized triplet host for complexes 1e3 because it has a high triplet energy and the mobilities of electron and hole are easily balanced [58]. The corresponding devices are named as A, B and C, respectively.…”

Novel nonplanar triphenylamine-centered oligofluorenes: Synthesis, thermal, photophysical and electrochemical properties

“…The large bathochromic shift combines with the decreased PL intensities can be related to the stabilization of the excited state. This behavior originating from the ICT process [19,20] is frequently observed in highly polarized molecules exhibiting enlarged dipoles and CT characters in their excited states. Moreover, the absorption peak exhibits solvent polarity independence, the solvatochromism may be more plausibly rationalized by the photo-induced electron transfer (PET) [21,22] process, suggesting that the ICT excited state has a larger dipolar moment compared with the ground state.…”