Decoration of Dibenzofuran Using Cyanocarbazole via 6‐Position as a Molecular Design Approach for High‐Triplet‐Energy Bipolar Host Materials

Abstract

In this study, two new dibenzofuran derivatives featuring one or two cyanocarbazole units, 6‐(dibenzo[b,d]furan‐4‐yl)‐9‐phenyl‐9H‐carbazole‐3‐carbonitrile (mBFCzCN) and 6,6′‐(dibenzo[b,d]furan‐4,6‐diyl)bis(9‐phenyl‐9H‐carbazole‐3‐carbonitrile) (dBFCzCN), were developed as host materials for phosphorescent organic light emitting diodes (PhOLEDs). A new molecular design connecting the cyanocarbazole to the dibenzofuran using the cyanocarbazole 6‐position instead of its 9‐position was created, and the effects of number of cyanocarbazole units in the dibenzofuran building block on the photophysical and electroluminescence properties were investigated in detail. The mBFCzCN compound revealed high triplet energy (2.78 eV) than that of dBFCzCN (2.68 eV) and good bipolar charge transporting properties. The potential of these materials as hosts for blue and green PhOLEDs was investigated using bis(4,6‐(difluorophenyl)pyridinato‐N,C2′)picolinate iridium(III) (FIrpic) and tris(2‐phenylpyridinato)iridium(III) (Ir(ppy)3) dopants, respectively. The results indicated that the mBFCzCN with one cyanocarbazole unit showed better device performance than the dBFCzCN with two cyanocarbazole units in the blue and green devices. High external quantum efficiencies of 19.0 and 21.2 % were demonstrated in the blue and green PhOLEDs with the mBFCzCN host due to its high triplet energy and good bipolar charge transporting characteristics.

Highly Efficient Phosphorescent Organic Light-Emitting Diodes Using Benzo[4′,5′]imidazo[2′,1′:2,3]imidazo[4,5,1-jk]carbazole as a Rigid and Effective Electron Acceptor in Bipolar Host

“…Researchers have proposed that incorporating both hole- and electron-transporting units in bipolar host materials can enhance device performance more rapidly than using conventional unipolar hosts. – Scientists have developed multiple classes of bipolar host materials by combining various hole-and electron-transporting moieties. Carbazoles and arylamines have been widely employed as hole-transporting units, – while benzimidazole, oxadiazoles, phenanthroline, phosphine oxide, phosphine sulfide, pyridine, triazine, and triazole have been used as electron-transporting units. However, further exploration of building units of bipolar hosts is necessary to improve the device performance of PhOLEDs.…”

Recent advances in catalytic oxidative reactions of phenols and naphthalenols

“…Moreover, 71 has proven to be a versatile synthon in materials chemistry for the synthesis of TDF materials (Scheme 31). 141,142 On the other hand, Oshima et al trifluoromethylketene dithioacetal monoxide with the aid of Tf 2 O via direct ortho-functionalization of C(sp 2 )-H. A variety of phenols were directly converted to the corresponding 2-methylthio-3-trifluoromethylbenzo[b]furans by the triflic anhydridemediated extended Pummerer annulation reaction. 143 Shi and co-workers developed the first copper-catalyzed oxidative annulation of phenols 54 and unactivated internal alkynes 72 to afford benzofurans 73.…”

“…Moreover, 71 has proven to be a versatile synthon in materials chemistry for the synthesis of TDF materials (Scheme 31). 141,142…”

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

“…Organic luminescent materials are extensively used in a wide range of optoelectronic devices. For the design of compounds, potentially exhibiting properties such as bipolar charge transport, delayed fluorescence or aggregation-induced emission enhancement (AIEE), a useful strategy is to employ both donor and acceptor moieties in a single molecular structure [1][2][3][4].…”