Red electrophosphorescence devices based on rhenium complexes

Abstract

Red electrophosphorescence from light-emitting devices based on two rhenium(I) diimine complexes, (4,4′-dimethyl formate-2,2′-bipyridine)Re(CO)3Cl (dmfbpy-Re) and (4,4′-dibutyl formate-2,2′-bipyridine)Re(CO)3Cl (dbufbpy-Re), is reported. N, N′-di-1-naphthyl-N, N′-diphenylbenzidine is used as the hole-transporting layer. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, bathocuproine is used to confine excitons within the luminescence zone. dmfbpy-Re and dbufbpy-Re are doped into the host materials (4,4′-N-N′-dicarbazole)biphenyl with mass ratios of 2%–20% as the light-emitting layer. Red emission from both complexes is achieved and the main peaks of both photoluminescence and electroluminescence are at about 610 nm. The turn-on voltage, maximum efficiency, and brightness for red emission achieved from the devices based on dmfbpy-Re and dbufbpy-Re are ∼5 V, 1.3 cd/A, and 582 cd/m2 and ∼4 V, 1.1 cd/A, and 739 cd/m2, respectively.

Device optimization of tris-aluminum (Alq3) based bilayer organic light emitting diode structures

“…Since some of the experimental factors may be difficult to control in a reliable and reproducible manner, it is difficult to ensure that all the fabricated devices would have the same emission region width. However, it is possible to artificially confine the excitons by insertion of an additional wide band gap organic layer such as bathocuproine, which is typically used in organic light emitting diodes and organic solar cells as a hole blocking or exciton blocking layer [23][24]. In such a manner, the width of the emission region can be made sufficiently narrow and very reproducible.…”

Recent Progresses on Materials for Electrophosphorescent Organic Light‐Emitting Devices

“…[ 159 ] The two butylformate groups at the 4 and 4 ′ positions of 2,2 ′ -bipyridine increased the steric hindrance effect and reduced the triplet-triplet annihilation of (4,4 ′ -dibutyl formate-2,2 ′ -bipyridine)Re(CO) 3 Cl (dbufbpyRe). [ 161 ] Red electrophosphorescence with a peak wavelength of ∼ 610 nm, a maximum effi ciency of 2.5 cd/A and a maximum brightness of 1852 cd/m 2 was obtained from the device of ITO/NPB 40 nm/2wt.% of dbufbpy-Re doped in CBP 30 nm/ BCP 30 nm/LiF 0.5 nm/Al. Even at a high current density of 100 mA/cm 2 , the effi ciency maintained at a value of 1.4 cd/A.…”

Synthesis, structure and luminescent properties of rhenium(I) carbonyl complexes containing pyrimidine-functionalized N-heterocyclic carbenes

“…The other introduces functional groups with electro-donating [31,32] or -accepting [33] properties into diimine ligands to improve the carrier-transporting ability of the Re(I) complexes in OLEDs and avoid the triplet-triplet annihilation due to the steric hindrance effect.…”