Operating lifetime of phosphorescent organic light emitting devices

Abstract

We investigate the continuous operating lifetime of organic light emitting devices (OLEDs) using the phosphorescent dopant, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (II) as the light emitting molecule. We characterize devices based on two different electron transporting hosts: tris-(8-hydroxyquinoline) aluminum and 4,4′-N,N′-dicarbazolyl-biphenyl (CBP). The OLEDs lose ∼25% of their luminance in the first 50 h of operation, followed by extremely slow degradation with negligible growth of dark spots. The device lifetime of CBP-based phosphorescent OLEDs projected to 50% initial brightness is >107 h at a mean current density of 10 mA/cm2 under 50% duty cycle pulsed operation. These extremely long lifetimes are speculated to be an intrinsic property of electrophosphorescent OLEDs, where radiative phosphors significantly shorten the lifetime of potentially reactive triplet states in the conductive host material.

Novel Electroluminescent Polymer Derived from Pyrene-Functionalized Polyaniline

“…26 In a 1 L round-bottomed flask, 250 mL of 1 M HCl was taken and 5 mL of aniline was added slowly with stirring. To this mixture, 250 mL of 1 M HCl containing ammonium persulfate (11.2 g) was added dropwise for [15][16][17][18][19][20] PANI salt powder (1.0 g) synthesized above was stirred in 100 mL aqueous sodium hydroxide solution (1.0 M) for 8 h at ambient temperature. PANI base powder was filtered, washed with excess water and finally with acetone and dried at 100 o C till a constant weight was reached.…”

“…There have been extensive studies on using low molecular weight complexes to make organic EL devices in order to achieve high brightness, multicolor emission, improved durability, and desired efficiency. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] From a materials perspective, organic light emitting diodes (OLEDs) are primarily prepared from either small molecules or polymers. [19][20][21][22] Small molecules are advantageous in that they can be highly purified and vacuum deposited in multilayer stacks, both important for display lifetime and efficiency.…”

Silicon-based organic light-emitting diode operating at a wavelength of 1.5 μm

“…3 Current devices now have efficiencies of Ͼ10% and extrapolated lifetimes of 10 7 h. 4 The use of rare earth containing organic compounds in such devices has been attracting increasing interest, particularly for visible emitters, due to the potential to increase efficiency and improve the color purity compared with some of the more traditional organic systems. 5,6 The use of organolanthanides to obtain infrared sources is also attracting more interest and devices containing erbium for 1.5 m emission, 7 neodymium for 0.9, 1, and 1.3 m emission 8,9 and ytterbium for 0.98 m emission 10 have now been demonstrated.…”

Small molecular and polymer organic light-emitting diodes based on novel iridium complex phosphor

“…To estimate these values in a reasonable amount of time, the accelerated testing conditions, both using higher luminance or higher temperature, are normally carried out. Some studies have been published [17,18], but the main mechanisms determining the degradation are still not well understood. The luminance degradation of both kind of organic devices (unencapsulated) were shown in Fig.…”