Bruns, M.

Hummel, H.

Kayser, S.

Nunney, T.

Peters, K.

Schabel, W.

Scharfer, P.

Tallarek, E.

English

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KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association XPS and ToF-SIMS sputter depth profiling of OLEDs  using Ar-cluster ion sources M. Bruns1, K. Peters2, T. Nunney3, E. Tallarek3, S. Kayser5, H. Hummel6, P. Scharfer2, W. Schabel2    1  Institute for Applied Materials & Karlsruhe Nano Micro Facility (KNMF) Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany  2 Institute of Thermal Process Engineering, Thin Film Technology (TFT) Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany 3 Thermo Fisher Scientific  Unit 24, The Birches Industrial Estate, East Grinstead, RH 19 1UB, UK 4 Tascon GmbH  Heisenbergstr. 15, D-48149 Münster, Germany 5 ION-TOF GmbH Heisenbergstr. 15, D-48149 Münster, Germany 6  Philips Technologie GmbH, Business Center OLED Lighting Aachen, Germany Corresponding author: michael.bruns@kit.edu Source: Holst Center 10-100 nm Introduction Research on organic light-emitting diodes (OLEDs) has gained much attention due to the potential for cheap and ultrathin illumination sources with high  color range.  In multilayer OLEDs the carrier injection efficiency from the electrodes into the light emitting layer is improved by layers for hole or electron transport and blocking. Vacuum evaporation is the standard method to produce precisely defined interfaces, but it is an expensive process with high material usage. Alternatively, the wet chemical processing has advantages in production cost, deposition rate and area.  But the solution process shows problems with the intermixing of the subsequently coated functional layers. The specific nature of small molecules used for OLEDs with their high mobility for diffusion in combination with low dry film thicknesses of only a few nanometers is challenging.  Multi Layer Deposition For a better understanding of the physical limitations of liquid-phase processed multilayer OLED structures, the possibility to characterise the material mixing between layers during coating and drying, and the comparison to evaporated layers is crucial. Source: TFT,KIT XPS: Mono Ar+ Ion Beam                                                                                         XPS: Ar-Cluster Ion Beam Pre-metered  coating method Slot coating (TSE/TFT) Self-metered  coating method Knife coating Evaporation: (multi) layer systems on glass slides                      Defined double layer                                               Mixed interlayer                           Mixed layer                                                                        Defined double layer  Coating solution of Material 2 onto dry layer of Material 1 on glass: N,N´-Di(naphth-1-yl)-N,N´diphenyl-benzidine Bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminium Material 1: NPB Material 2: BAlq  Solution: (multi) layer systems on glass slides                                               Defined double layer                                                                         Mixed layer   Orthogonal solvent  Solvent with high solubility   Similar profiles for evaporation and solution approach ToF-SIMS: Ar-Cluster Ion Beam  Experimental Thermo Fisher Scientific K-Alpha XPS-Instrument • Micro-focussed monochromatic AlKα X-ray source • Monatomic and gas cluster ion source (MAGCIS), 6 keV, cluster size: 2000 atoms  • Ar+-ion source, 2 keV ION-TOF GmbH ToF.SIMS5  Spectrometer • 25 keV Bi3+ primary ions; positive polarity • Gas cluster ion source (GCIS), 5 keV, cluster size: 1000 atoms  Conclusions  High mass Ar cluster ion sources for both XPS and ToF-SIMS enabling sputter depth profiling of organic materials while preserving the chemical/molecular information  Layer deposition via solution process provides defined multi layer systems  Solution                                   Evaporation                            Evaporation                             Evaporation                   Defined double layer                                             Mixed interlayer                           Mixed layer   Mono Ar+ and Ar-cluster ion beam sputter depth profiling reveal comparable elemental in-depth distribution   Preserved chemical depth information only with Ar-cluster ion beam:  XPS sputter depth profile:  C-C/C-N,O ratios agree with theoretical values for NPB and BAlq π−π* peak indicates non-decomposed aromatics   ToF-SIMS sputter depth profile:  stable detection of the molecular NPB+ ion C44H32N2+ BAlq             NPB BAlq             NPB BAlq    mixed     NPB BAlq             NPB BAlq             NPB BAlq               NPB BAlq    mixed  NPB 

XPS and ToF-SIMS sputter depth profiling of OLEDs using Ar-cluster ion sources

https://publikationen.bibliothek.kit.edu/220093058/3816382

XPS and ToF-SIMS sputter depth profiling of OLEDs using Ar-cluster ion sources

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