Derivatives of Imidazole and Carbazole as Bifunctional Materials for Organic Light-Emitting Diodes

Abstract

New derivatives of carbazole and diphenyl imidazole for potential multiple applications were synthesized and investigated. Their properties were studied by thermal, optical, photophysical, electrochemical, and photoelectrical measurements. The compounds exhibited relatively narrow blue light-emission bands, which is favorable for deep-blue electroluminescent devices. The synthesized derivatives of imidazole and carbazole were tested as fluorescent emitters for OLEDs. The device showed deep-blue emissions with CIE color coordinates of (0.16, 0.08) and maximum quantum efficiency of 1.1%. The compounds demonstrated high triplet energy values above 3.0 eV and hole drift mobility exceeding 10−4 cm2/V·s at high electric fields. One of the compounds having two diphenyl imidazole moieties and tert-butyl-substituted carbazolyl groups showed bipolar charge transport with electron drift mobility reaching 10−4 cm2/V·s at electric field of 8 × 105 V/cm. The synthesized compounds were investigated as hosts for green, red and sky-blue phosphorescent OLEDs. The green-, red- and sky-blue-emitting devices demonstrated maximum quantum efficiencies of 8.3%, 6.4% and 7.6%, respectively.

Novel Fluorescent Tetrahedral Zinc (II) Complexes Derived from 4-Phenyl-1-octyl-1H-imidazole Fused with Aryl-9H-Carbazole and Triarylamine Donor Units: Synthesis, Crystal Structures, and Photophysical Properties

“…Examples of N-heterocyclic systems, such as imidazole and its derivatives, have piqued the curiosity of researchers interested in developing hybrid organic-inorganic systems for various applications [2,[14][15][16][17][18]. The unique properties of imidazole-based complexes, such as excellent electrochemical and photoluminescent properties, excellent thermal properties, and ease of modification, were taken into account in the design of various host materials such as electron transport, fluorescent, or phosphorescent molecules [19][20][21][22][23].…”

“…On the other hand, carbazole and diarylamine units are often regarded as important electron-donating units in donor-acceptor systems (D-A) due to their high triplet energies and good hole-transport properties [1,15,16,[30][31][32][33]. The diarylamine structure consists of two benzene groups directly attached to the central nitrogen atom, while the carbazole structure is a tricyclic ring skeleton with pyrrole rings attached to two aromatic rings.…”

“…The diarylamine structure consists of two benzene groups directly attached to the central nitrogen atom, while the carbazole structure is a tricyclic ring skeleton with pyrrole rings attached to two aromatic rings. These high photoluminescence efficiency, electron-rich, and inexpensive starting materials can be easily modified by substituting the central nitrogen atom [1,15,16,[30][31][32][33][34][35]. Therefore, the carbazole and diarylamine frameworks remain good templates for the fabrication of OLED emitters and transparent optoelectronic materials.…”