1‐Methyl‐2‐(anthryl)‐imidazo[4,5‐f][1,10]‐phenanthroline: A Highly Efficient Electron‐Transport Compound and a Bright Blue‐Light Emitter for Electroluminescent Devices

Abstract

A new organic blue‐light emitter 1‐methyl‐2‐(anthryl)‐imidazo[4,5‐f][1,10]‐phenanthroline (1) has been synthesized and fully characterized. The utility of compound 1 as a blue‐light emitter in electroluminescent (EL) devices has been evaluated by fabricating a series of EL devices A where compound 1 functions as an emitter. The EL spectrum of device series A has the emission maximum at 481 nm with the CIE (Commission Internationale de l'Eclairage) color coordinates 0.198 and 0.284. The maximum luminance of devices in series A is 4000 cd m–2 and the best external quantum efficiency of device series A is 1.82 %. The utility of compound 1 as an electron injection–electron transport material has been evaluated by constructing a set of EL devices B where 1 is used as either the electron‐injection layer or the electron injection–electron transport layer. The performance of device series B is compared to the standard device in which Alq3 (tris(8‐hydroxyquinoline) aluminum) is used as the electron injection–electron transport layer. The experimental results show that the performance of 1 as an electron injection–electron transport material is considerably better than Alq3. The stability of device series B is comparable to that of the standard Alq3 device. The excellent performance of 1 as an electron injection/transport material may be attributed to the strong intermolecular interactions of 1 in the solid state as revealed by single‐crystal X‐ray diffraction analysis. In addition, compound 1 is a colorless material with a much larger highest occupied molecular orbital–lowest unoccupied molecular (HOMO–LUMO) gap than Alq3, which renders it potentially useful for a wide range of applications in EL devices.

Diboron and Triboron Compounds Based on Linear and Star-Shaped Conjugated Ligands with 8-Hydroxyquinolate Functionality: Impact of Intermolecular Interaction and Boron Coordination on Luminescence

“…Again, the thienyl-containing ligand L5 has the lowest quantum yield in the solid state. Intermolecular π−π interactions that significantly red-shift emission energy and lower the emission quantum yield have been frequently observed previously . Although molecules L1 − L4 are bright blue emitters in solution and have a high thermal stability, the strong intermolecular interactions in the solid-state hamper their use as blue emitters in OLEDs because of the low quantum efficiency in the solid state.…”

Diphenanthroline Electron Transport Materials for the Efficient Charge Generation Unit in Tandem Organic Light-Emitting Diodes

“…Similarly, a well-known ETL material (TmPyPB), possessing high electron mobility, also exhibits a large red-shifted PL spectrum in the film state. These kinds of large red shifts in the film state PL generally occurred in an organic matrix with close intermolecular interaction between the neighboring molecules. − As shown in Figure a, the 3D molecular structures of m -bPPhenB, p -bPPhenB, and TmPyPB have wide and planar molecular shapes, which are favorable for a horizontal molecular orientation and molecular packing. The molecular planarity of the three molecules is in the order p -bPPhenB > m -bPPhenB > TmPyPB, and the magnitude of the red shift shows the same tendency as the planarity.…”

Blue light-emitting and electron-transporting materials based on dialkyl-functionlized anthracene imidazophenanthrolines

“…Herein, we have found that the compound 1 has similar HOMO level with MAIP, 15 indicating that the tert-butyl units have negligible electronic effect on the anthracene. The LUMO values for compounds 1 and 2 were calculated based on their respective band gap energy obtained from the tail-end of their UVevis absorptions and the HOMO values (Table 1).…”

“…In comparison, the film state emission of MAIP is red shifted by 49 nm (Table 1) compared to the solution state because of strong aggregation of the compound through pep* interaction of anthracenyl units. 15 It is possible that the two tert-butyl groups effectively suppress similar pÀp* interaction at the anthracenyl units in BAIP and 2. The blue shift of BAIP and 2 may be due to H-type aggregation of imidazophenanthroline units, or less intermolecular interaction of the dyes in the film state compared to the interaction of the dye molecule with the solvent.…”

“…The absorption profile of the compounds is basically the superposition of 2,6-di-tert-butylanthracene and imidazophenanthroline units. 14,15 The dilute solution of BAIPs in dichloromethane (ca. 4Â10 À5 M) exhibits a blue emission between 456 and 503 nm (Table 1), and the quantum yield reaches 0.78 for 1 and 0.47 for 2, with the full widths at half maximum (FWHM) of ca.…”