Investigation of energy transfer mechanisms between two adjacent phosphorescent emission layers

The investigation of energy transfer mechanisms between two adjacent phosphorescent emission layers comprising the green emitter molecule fac-tris(2-phenly-pyridin)iridium (Ir(ppy)3) and the red emitter molecule iridium(III)bis(2-methyldibenzo[f,h]quinoxaline(acetylacetonate) (Ir(MDQ)2(acac)) is presented. We show that the performance can be enhanced by a variation of the emission layer thickness and the emitter concentration. By inserting different interlayer materials between the emission units, we demonstrate that triplet excitons are formed on the Ir(ppy)3 and subsequently transferred to the Ir(MDQ)2(acac) molecules via the hole transporting host material N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine of the red emission layer. The variation of the interlayer thickness shows that the triplet diffusion length is several tens of nanometers. After optimization of the guest-host system an efficiency enhancement by 15% was achieved and the lifetime of the red-green emissive unit could be enhanced by ...

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

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

[3]  Jeong-Ik Lee,et al.  Improvements of phosphorescent white OLEDs performance for lighting application. , 2008, Journal of nanoscience and nanotechnology.

[4]  A. Dodabalapur,et al.  Light amplification in organic thin films using cascade energy transfer , 1997, Nature.

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

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

[7]  William James Begley,et al.  60.1: Invited Paper: Tandem Hybrid White OLED Devices with Improved Light Extraction , 2009 .

[8]  Andreas Bräuer,et al.  Dipole lifetime in stratified media , 2002 .

[9]  Stephen R. Forrest,et al.  Efficient Organic Electrophosphorescent White‐Light‐Emitting Device with a Triple Doped Emissive Layer , 2004 .

[10]  Gregor Schwartz,et al.  White organic light-emitting diodes with fluorescent tube efficiency , 2009, Nature.

[11]  Stephen R. Forrest,et al.  Phosphorescent materials for application to organic light emitting devices , 1999 .

[12]  Heike Riel,et al.  Investigation of internal processes in organic light-emitting devices using thin sensing layers , 2003 .

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

[14]  J. Staudigel,et al.  A quantitative numerical model of multilayer vapor-deposited organic light emitting diodes , 1999 .

[15]  Jan Birnstock,et al.  High-efficiency and low-voltage p‐i‐n electrophosphorescent organic light-emitting diodes with double-emission layers , 2004 .

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

[17]  Gregor Schwartz,et al.  Reduced efficiency roll-off in high-efficiency hybrid white organic light-emitting diodes , 2008 .

[18]  Hong-Seok Choi,et al.  60.3: Two‐Stacked White Organic Light‐Emitting Diodes Consisting of Fluorescent and Phosphorescent Hybrid Structure with High Efficiency and Good Color Characteristics , 2009 .

[19]  Chihaya Adachi,et al.  Intermolecular interaction and a concentration-quenching mechanism of phosphorescent Ir(III) complexes in a solid film. , 2006, Physical review letters.

[20]  Stefan Nowy,et al.  Efficiency analysis of organic light-emitting diodes based on optical simulation , 2009 .

[21]  Stephen R. Forrest,et al.  EXCITONIC SINGLET-TRIPLET RATIO IN A SEMICONDUCTING ORGANIC THIN FILM , 1999 .

[22]  Gregor Schwartz,et al.  Triplet Harvesting in Hybrid White Organic Light‐Emitting Diodes , 2009 .

[23]  A. Fick.  V. On liquid diffusion , 1855 .

[24]  Hany Aziz,et al.  Organic light emitting devices with enhanced operational stability at elevated temperatures , 2002 .

[25]  Junji Kido,et al.  Highly Efficient Organic Blue‐and White‐Light‐Emitting Devices Having a Carrier‐ and Exciton‐Confining Structure for Reduced Efficiency Roll‐Off , 2008 .

[26]  D. L. Dexter.  A Theory of Sensitized Luminescence in Solids , 1953 .

[27]  T. Főrster,et al.  10th Spiers Memorial Lecture. Transfer mechanisms of electronic excitation , 1959 .