Operational stability of electrophosphorescent devices containing p and n doped transport layers

The operational stability of low-operating voltage p-i-n electrophosphorescent devices containing fac-tris(2-phenylpyridine) iridium as the emissive dopant is investigated. In these devices, Li-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) served as an n-type electron transport layer, or as an undoped hole blocking layer (HBL), and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane doped 4,4′,4″-tris(3-methylphenylphenylamino) triphenylamine served as a p-type hole transport layer. The glass transition temperature of BPhen can be increased by the addition of aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq), resulting in improved morphological stability, thereby reducing device degradation. When thermally stable BAlq was used as a HBL in both p-i-n and undoped devices, the extrapolated operational lifetime (normalized to an initial luminance of 100 cd/m2) of the p-i-n and undoped devices are 18 000 and 60 000 h, respectively, indicating that the presence of p and n dopants can accelerate...

[1]  Stephen R. Forrest,et al.  Lithium doping of semiconducting organic charge transport materials , 2001 .

[2]  Stephen R. Forrest,et al.  Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques. , 1997, Chemical reviews.

[3]  Xu,et al.  Degradation mechanism of small molecule-based organic light-emitting devices , 1999, Science.

[4]  Raymond Kwong,et al.  Graded mixed-layer organic light-emitting devices , 2002 .

[5]  J. Curless,et al.  Organic light-emitting diodes with a bipolar transport layer , 1999 .

[6]  Stephen R. Forrest,et al.  High operational stability of electrophosphorescent devices , 2002 .

[7]  Stephen R. Forrest,et al.  Thermally induced failure mechanisms of organic light emitting device structures probed by X-ray specular reflectivity , 1997 .

[8]  Martin Pfeiffer,et al.  Low-voltage organic electroluminescent devices using pin structures , 2002 .

[9]  Hany Aziz,et al.  Reliability and degradation of small molecule-based organic light-emitting devices (OLEDs) , 2002 .

[10]  Stephen R. Forrest,et al.  Efficient photon harvesting at high optical intensities in ultrathin organic double-heterostructure photovoltaic diodes , 2000 .

[11]  S. Forrest,et al.  Reliability and degradation of organic light emitting devices , 1994 .

[12]  Ching Wan Tang,et al.  Organic electroluminescent devices with improved stability , 1996 .

[13]  David J. Williams,et al.  Polymer science and engineering , 1971 .

[14]  H. Kanai,et al.  Operation characteristics and degradation of organic electroluminescent devices , 1998 .

[15]  Yang Yang,et al.  Degradation mechanism of phosphorescent-dye-doped polymer light-emitting diodes , 2001 .

[16]  M. Thompson,et al.  Thermally Stable Hole‐Transporting Materials Based upon a Fluorene Core , 2002 .