Ambipolar Conductive 2,7‐Carbazole Derivatives for Electroluminescent Devices

Abstract

A series of 2,7‐disubstituted carbazole (2,7‐carb) derivatives incorporating arylamines at the 2 and 7 positions are synthesized via palladium‐catalyzed C–N or C–C bond formation. These compounds possess glass transition temperatures ranging from 87 to 217 °C and exhibit good thermal stabilities, with thermal decomposition temperatures ranging from 388 to 480 °C. They are fluorescent and emit in the purple‐blue to orange region. Two types of organic light emitting diodes (OLEDs) were constructed from these compounds: (I) indium tin oxide (ITO)/2,7‐carb (40 nm)/1,3,5‐tris(N‐phenylbenzimidazol‐2‐yl)benzene (TPBI, 40 nm)/Mg:Ag; and (II) ITO/2,7‐carb (40 nm)/tris(8‐hydroxyquinoline) aluminum (Alq3, 40 nm)/Mg:Ag. In type I devices, the 2,7‐disubstituted carbazoles function as both hole‐transporting and emitting material. In type II devices, light is emitted from either the 2,7‐disubstituted carbazole layer or Alq3. The devices appear to have a better performance compared to devices fabricated with their 3,6‐disubstituted carbazole congeners. Some of the new compounds exhibit ambipolar conductive behavior, with hole and electron mobilities up to 10–4 cm2 V–1 s–1.

Conducting Polymers as Anode Buffer Materials in Organic and Perovskite Optoelectronics

“…Efficient OLEDs use multilayer structures to improve charge carrier injection and charge balance. Especially, to overcome the high energy barrier between anode and overlying organic semiconducting layer and to facilitate charge injection to this layer, various anode buffer layers have been introduced in OLEDs and PeLEDs …”

“…Organic small‐molecules are commonly used as hole injection or hole transporting layers in optoelectronics devices . However, the standard fabrication of thin organic small‐molecule films by vacuum thermal evaporation is expensive.…”

Synthesis, characterization and applications of vinylsilafluorene copolymers: New host materials for electroluminescent devices

“…The prominent class of host materials is carbazole [7][8][9][10] which has sufficiently high triplet energy to be able to host red, green, and even blue triplet emitters. For small-molecule OLEDs, 4,4′-bis (9-carbazolyl)-biphenyl (CBP) is often used [6,11].…”

Efficient OLEDs Fabricated by Solution Process Based on Carbazole and Thienopyrrolediones Derivatives

“…The carbazole unit is considered a virtuous building block for SMs with optoelectronics properties because of its good transportation of holes, amorphous film-forming properties, high triplet energy and good thermal stability [ 13 ]. Many organic materials for the fabrication of blue (or greenish blue) OLEDs are carbazole derivatives, which are used mainly as host materials [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ] and in other cases, as emissive layer (EML) [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Previous studies of OLEDs fabrication based on carbazole derivatives have highlighted the great potential of them [ 35 ], for instance, S. Wang et al [ 21 ] showed the use of G3MP, a carbazole derivative, as host in the fabrication of OLEDs with ITO/PEDOT:PSS/G3MP:G0/SPPO13/LiF/Al architecture, reporting high current efficiencies up to and maximum luminances of (at 18 V); M. Zhang et al [ 36 ] reported OLEDs fabricated through solution process using TCBzC, a carbazole derivative, as emissive layer under the configuration ITO/PEDOT:PSS/TCBzC/TPBi/LiF/Al with a turn on voltage of 2.5 V, maximum luminances of 9226 cd/m 2 and current efficiencies up to31.6 cd/A.…”