Low roll-off power efficiency organic light-emitting diodes consisted of nondoped ultrathin phosphorescent layer

Low roll-off power efficiency (ηp) organic light-emitting diodes at high current density were fabricated using a nondoped ultrathin bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2′] iridium (acetylacetonate) phosphorescent layer and thin N,N′-di(naphthalene-2-yl)-N,N′-diphenyl-benzidine separate layer. A maximum ηp of 8.48lm∕W and luminance efficiency of 20.26cd∕A at 2014cd∕m2 were obtained from the device. The ηp roll-off percentage of ultrathin phosphor layer device was reduced to 20% at a current density of 20mA∕cm2, which is about 40% for conventional phosphorescent device. The low roll off of efficiency was attributed to the direct carrier trapping and confining emission zone function of the ultrathin phosphor layer.

[1]  Jan Kalinowski,et al.  Triplet energy exchange between fluorescent and phosphorescent organic molecules in a solid state matrix , 2004 .

[2]  Shigeki Naka,et al.  Nondoped-type white organic electroluminescent devices utilizing complementary color and exciton diffusion , 2002 .

[3]  Wei Li,et al.  High-Efficiency White Organic Light-Emitting Diodes Based on Phosphorescent Iridium Complex and 4,4'-Bis[N-1-napthyl-N-phenyl-amino]biphenyl Emitters , 2007 .

[4]  White organic light-emitting diodes with fine chromaticity tuning via ultrathin layer position shifting , 2006, physics/0609238.

[5]  S. Forrest,et al.  Nearly 100% internal phosphorescence efficiency in an organic light emitting device , 2001 .

[6]  Wenqing Zhu,et al.  Study of blue organic light emitting diode by inserting a red dye ultra thin layer at the emitting layer , 2005 .

[7]  K. Leo,et al.  Single-step triplet-triplet annihilation: an intrinsic limit for the high brightness efficiency of phosphorescent organic light emitting diodes. , 2007, Physical review letters.

[8]  Stephen R. Forrest,et al.  Transient analysis of organic electrophosphorescence. II. Transient analysis of triplet-triplet annihilation , 2000 .

[9]  Jang‐Joo Kim,et al.  Low roll-off of efficiency at high current density in phosphorescent organic light emitting diodes , 2007 .

[10]  M. Wong,et al.  Efficiency improvement of phosphorescent organic light-emitting diodes using semitransparent Ag as anode , 2006 .

[11]  Pengfei Wang,et al.  Highly Efficient Non‐Doped Blue Organic Light‐Emitting Diodes Based on Fluorene Derivatives with High Thermal Stability , 2005 .

[12]  Karsten Walzer,et al.  Triplet-exciton quenching in organic phosphorescent light-emitting diodes with Ir-based emitters , 2007 .

[13]  Junsheng Yu,et al.  Low operating voltage bright organic light-emitting diode using iridium complex doped in 4,4 ' -bis[N-1-napthyl-N-phenyl-amino]biphenyl , 2007 .

[14]  Jan Kalinowski,et al.  Quenching effects in organic electrophosphorescence , 2002 .

[15]  Masatoshi Tokita,et al.  A Novel Blue Light Emitting Diode Using Tris(2,3-methyl-8-hydroxyquinoline) Aluminum(III) as Emitter , 1999 .

[16]  J. Kalinowski,et al.  Highly efficient organic electrophosphorescent light-emitting diodes with a reduced quantum efficiency roll off at large current densities , 2004 .

[17]  Stephen R. Forrest,et al.  The path to ubiquitous and low-cost organic electronic appliances on plastic , 2004, Nature.

[18]  Jan Kalinowski,et al.  Single-dopant organic white electrophosphorescent diodes with very high efficiency and its reduced current density roll-off , 2007 .

[19]  Stephen R. Forrest,et al.  Management of singlet and triplet excitons for efficient white organic light-emitting devices , 2006, Nature.

[20]  Junsheng Yu,et al.  High efficiency organic light-emitting diodes with yellow phosphorescent emission based on a novel iridium complex , 2007 .