Measuring the light emission profile in organic light-emitting diodes with nanometre spatial resolution

Determining the precise shape of the emission profile across the thickness of the active layer in organic light-emitting diodes is of importance for device optimization and assessing the validity of advanced device models. We present a comprehensive method for accurately measuring the shape of the emission profile, the intrinsic spectrum of emitting dipoles and the emitting dipole orientation. The method uses a microcavity light outcoupling model, which includes self-absorption and optical anisotropy, and is based on the full wavelength, angle and polarization resolved emission intensity. Application to blue (polyfluorene-based) and orange-red (NRS-PPV) polymer organic light-emitting diodes reveals a peaked shape of the emission profile. A significant voltage and layer thickness dependence of the peak positions is observed, with a demonstrated resolution better than 5 nm.

[1]  Sailing He,et al.  Efficient and Rigorous Modeling of Light Emission in Planar Multilayer Organic Light-Emitting Diodes , 2007, Journal of Display Technology.

[2]  Stephen R. Forrest,et al.  Weak microcavity effects in organic light-emitting devices , 1998 .

[3]  P. Blom,et al.  Exciton quenching in poly(phenylene vinylene) polymer light-emitting diodes , 2005 .

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

[5]  Kristiaan Neyts,et al.  Simulation of light emission from thin-film microcavities , 1998 .

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

[7]  A. Monkman,et al.  Direct measurement of the singlet generation yield in polymer light-emitting diodes. , 2006, Physical Review Letters.

[8]  R. Coehoorn,et al.  Electron transport in polyfluorene-based sandwich-type devices: Quantitative analysis of the effects of disorder and electron traps , 2009 .

[9]  Richard H. Friend,et al.  Effect of metal films on the photoluminescence and electroluminescence of conjugated polymers , 1997 .

[10]  Olivier J. F. Martin,et al.  Numerical modeling of light emission and propagation in organic LEDs using the Green's tensor , 2004, SPIE Optics + Photonics.

[11]  R. Friend,et al.  Modelling of interference effects in anisotropic conjugated polymer devices , 2000 .

[12]  Beat Ruhstaller,et al.  Thickness-dependent changes in the optical properties of PPV- and PF-based polymer light emitting diodes , 2003 .

[13]  Stefan Nowy,et al.  Light extraction and optical loss mechanisms in organic light-emitting diodes: Influence of the emitter quantum efficiency , 2008 .

[14]  Michael Kiy,et al.  59.1: Invited Paper: Optoelectronic OLED Modeling for Device Optimization and Analysis , 2007 .

[15]  H. Greiner,et al.  Measurement and modeling of carrier transport and exciton formation in blue polymer light emitting diodes , 2006, SPIE Photonics Europe.

[16]  Simone I. E. Vulto,et al.  Modification of PEDOT:PSS As Hole Injection Layer in Polymer LEDs , 2004 .

[17]  L. Pettersson,et al.  Determination of the emission zone in a single-layer polymer light-emitting diode through optical measurements , 2001 .

[18]  M. Tomaš,et al.  Decay of excited molecules in absorbing planar cavities , 1997 .

[19]  Gregor Schwartz,et al.  Harvesting Triplet Excitons from Fluorescent Blue Emitters in White Organic Light‐Emitting Diodes , 2007 .

[20]  X. Tao,et al.  Flexible organic light-emitting diodes with a polymeric nanocomposite anode , 2008, Nanotechnology.

[21]  Chun Lin,et al.  Realizing white phosphorescent 100 lm/W OLED efficacy , 2008, Optics & Photonics - Photonic Devices + Applications.

[22]  George G. Malliaras,et al.  The roles of injection and mobility in organic light emitting diodes , 1998 .

[23]  Johan Frederik Dijksman,et al.  Towards large‐area full‐color active‐matrix printed polymer OLED television , 2005 .

[24]  Norbert Danz,et al.  Measuring the profile of the emission zone in polymeric organic light-emitting diodes , 2009 .

[25]  R. Coehoorn,et al.  Hole transport in polyfluorene-based sandwich-type devices : quantitative analysis of the role of energetic disorder , 2008 .

[26]  Yong Cao,et al.  Improved quantum efficiency for electroluminescence in semiconducting polymers , 1999, Nature.

[27]  A. Heeger,et al.  Flexible light-emitting diodes made from soluble conducting polymers , 1992, Nature.

[28]  Russell J. Holmes,et al.  Excitonic singlet-triplet ratios in molecular and polymeric organic materials , 2003 .

[29]  S. Jeon,et al.  Highly efficient single-layer phosphorescent white organic light-emitting diodes using a spirofluorene-based host material. , 2009, Optics letters.

[30]  A. Heeger,et al.  Microstructure of thin films of photoluminescent semiconducting polymers , 1998 .

[31]  A. S. Dhoot,et al.  Spin-dependent exciton formation in π-conjugated compounds , 2001, Nature.

[32]  Stephen R. Forrest,et al.  White Organic Light‐Emitting Devices for Solid‐State Lighting , 2004 .

[33]  Richard H. Friend,et al.  Electroluminescence emission pattern of organic light-emitting diodes: Implications for device efficiency calculations , 2000 .

[34]  Richard H. Friend,et al.  Interference effects in anisotropic optoelectronic devices , 2000 .

[35]  J. Sturm,et al.  Optimization of external coupling and light emission in organic light-emitting devices: modeling and experiment , 2002 .

[36]  James L. Auld,et al.  Degradation in blue-emitting conjugated polymer diodes due to loss of ohmic hole injection , 2004 .

[37]  Stefan Nowy,et al.  Light extraction and optical loss mechanisms in organic light-emitting diodes , 2008, SPIE Photonics Europe.