Unified analysis of transient and steady-state electrophosphorescence using exciton and polaron dynamics modeling

Phosphorescent organic light-emitting devices (OLEDs) can suffer a significant reduction in device efficiency under high current density excitation. This steady-state efficiency roll-off is frequently modeled by including losses from exciton-exciton and exciton-polaron quenching. Despite success in modeling the steady-state efficiency roll-off, the corresponding transient electroluminescence behavior has not been modeled as effectively using the same quenching processes. In this work, both the steady-state and transient electroluminescence behavior of phosphorescent OLEDs based on tris[2-phenylpyridinato-C2,N]Iridium(III) (Ir(ppy)3) are successfully reproduced by considering a dynamic polaron population. Within this model, polarons are able to either form excitons or leak through the device emissive layer, reducing the overall efficiency. This formalism permits a natural and rigorous connection between exciton and polaron dynamics and device charge balance, with the charge balance cast as the efficiency o...

[1]  J. Kalinowski,et al.  Triplet exciton interactions in solid films of an electrophosphorescent Pt (II) porphyrin , 2005 .

[2]  Stephen R. Forrest,et al.  Improved energy transfer in electrophosphorescent devices , 1999 .

[3]  Mikhail A. Parshin,et al.  Charge carrier mobility in CBP films doped with Ir(ppy)3 , 2006, SPIE Photonics Europe.

[4]  P. Ruden,et al.  Electrostatic capacitance in single and double layer organic diodes , 2012 .

[5]  Stephen R. Forrest,et al.  Blue organic electrophosphorescence using exothermic host–guest energy transfer , 2003 .

[6]  H. Bouchriha,et al.  Transient response of a bilayer organic electroluminescent diode: Experimental and theoretical study of electroluminescence onset , 2001 .

[7]  S. Shaheen,et al.  Bright blue organic light-emitting diode with improved color purity using a LiF/Al cathode , 1998 .

[8]  Walter Riess,et al.  Simulating electronic and optical processes in multilayer organic light-emitting devices , 2003 .

[9]  H. Aziz,et al.  Causes of efficiency roll-off in phosphorescent organic light emitting devices: Triplet-triplet annihilation versus triplet-polaron quenching , 2010 .

[10]  H. Bouchriha,et al.  Study of the transient EL slow rise in single layer OLEDs , 2006 .

[11]  K. Walzer,et al.  Direct observation of host–guest triplet–triplet annihilation in phosphorescent solid mixed films , 2009 .

[12]  J. Amagai,et al.  A dynamic model for injection and transport of charge carriers in pulsed organic light-emitting diodes , 2004 .

[13]  Stephen R. Forrest,et al.  Quantum efficiency roll-off at high brightness in fluorescent and phosphorescent organic light emitting diodes , 2008 .

[14]  Stephen R. Forrest,et al.  Efficient electrophosphorescence using a doped ambipolar conductive molecular organic thin film , 2001 .

[15]  S. Forrest,et al.  Highly efficient phosphorescent emission from organic electroluminescent devices , 1998, Nature.

[16]  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.

[17]  W. Stampor,et al.  Electric field effect on luminescence efficiency in 8-hydroxyquinoline aluminum (Alq3) thin films , 1997 .

[18]  Chihaya Adachi,et al.  100% phosphorescence quantum efficiency of Ir(III) complexes in organic semiconductor films , 2005 .

[19]  H. Aziz,et al.  Modification of Exciton Lifetime by the Metal Cathode in Phosphorescent OLEDs, and Implications on Device Efficiency and Efficiency Roll‐off Behavior , 2011 .

[20]  R. Holmes,et al.  Engineering Efficiency Roll‐Off in Organic Light‐Emitting Devices , 2014 .

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

[22]  A. Penzkofer,et al.  Photoluminescence Characteristics of Ir(ppy)3 and PtOEP doped in TPD Host Material , 2006 .

[23]  Baohua Zhang,et al.  High‐Efficiency Single Emissive Layer White Organic Light‐Emitting Diodes Based on Solution‐Processed Dendritic Host and New Orange‐Emitting Iridium Complex , 2012, Advanced materials.

[24]  Lewis J. Rothberg,et al.  Status of and prospects for organic electroluminescence , 1996 .

[25]  Tetsuo Tsutsui,et al.  High Quantum Efficiency in Organic Light-Emitting Devices with Iridium-Complex as a Triplet Emissive Center , 1999 .

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

[27]  M. Lampert.  Volume-controlled current injection in insulators , 1964 .

[28]  J. J. M. Vleggaar,et al.  Electron and hole transport in poly(p‐phenylene vinylene) devices , 1996 .

[29]  Karl Leo,et al.  Efficiency and rate of spontaneous emission in organic electroluminescent devices , 2012 .

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

[31]  Richard H. Friend,et al.  Transient electroluminescence of polymer light emitting diodes using electrical pulses , 1999 .

[32]  Caroline Murawski,et al.  Efficiency Roll‐Off in Organic Light‐Emitting Diodes , 2013, Advanced materials.

[33]  Walter Riess,et al.  Transient and steady-state behavior of space charges in multilayer organic light-emitting diodes , 2001 .

[34]  Karl Leo,et al.  Outcoupling efficiency in small-molecule OLEDs: from theory to experiment , 2010, OPTO.

[35]  S. R. Forrest,et al.  High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer , 2000, Nature.

[36]  M. Weaver,et al.  Direct evidence for degradation of polaron excited states in organic light emitting diodes , 2009 .