Quantitative analysis of charge transport in intrinsic and doped organic semiconductors combining steady-state and frequency-domain data

Single-carrier devices are an excellent model system to study charge injection and charge transport properties of (doped) transport layers and to draw conclusions about organic electronics devices in which they are used. By combining steady-state and impedance measurements at varying temperatures of hole-only devices with different intrinsic layer thicknesses, we are able to determine all relevant material parameters, such as the charge mobility and the injection barrier. Furthermore, the correlation and sensitivity analyses reveal that the proposed approach to study these devices is especially well suited to extract the effective doping density, a parameter which cannot be easily determined otherwise. The effective doping density is crucial in organic light-emitting diodes (OLEDs) for realizing efficient injection, charge balance, and lateral conductivity in display or lighting applications. With the fitted drift-diffusion device model, we are further able to explain the extraordinary two-plateau capacitance–frequency curve of these hole-only devices, which originates from charges that flow into the intrinsic layer at zero applied offset voltage. We demonstrate that the observation of this behaviour is a direct indication for ideal charge injection properties and the observed capacitance–frequency feature is linked to the charge carrier mobility in the intrinsic layer. The extracted material parameters may directly be used to simulate and optimize full OLED devices employing the investigated hole-injection and -transport materials.Single-carrier devices are an excellent model system to study charge injection and charge transport properties of (doped) transport layers and to draw conclusions about organic electronics devices in which they are used. By combining steady-state and impedance measurements at varying temperatures of hole-only devices with different intrinsic layer thicknesses, we are able to determine all relevant material parameters, such as the charge mobility and the injection barrier. Furthermore, the correlation and sensitivity analyses reveal that the proposed approach to study these devices is especially well suited to extract the effective doping density, a parameter which cannot be easily determined otherwise. The effective doping density is crucial in organic light-emitting diodes (OLEDs) for realizing efficient injection, charge balance, and lateral conductivity in display or lighting applications. With the fitted drift-diffusion device model, we are further able to explain the extraordinary two-plateau capacit...

[1]  R. Scholz,et al.  Quantitative description of charge-carrier transport in a white organic light-emitting diode , 2011 .

[2]  T. Riedl,et al.  p-type doping efficiency of MoO3 in organic hole transport materials , 2009 .

[3]  P. Murgatroyd,et al.  Theory of space-charge-limited current enhanced by Frenkel effect , 1970 .

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

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

[6]  S. So,et al.  Determination of carrier mobility in phenylamine by time-of-flight, dark-injection, and thin film transistor techniques , 2008 .

[7]  N. Greenham,et al.  Temperature-dependent electron and hole transport in disordered semiconducting polymers: Analysis of energetic disorder , 2010 .

[8]  Beat Ruhstaller,et al.  The role of shallow traps in dynamic characterization of organic semiconductor devices , 2012 .

[9]  J. Kǒcka,et al.  Extraction current transients: new method of study of charge transport in microcrystalline silicon , 2000, Physical review letters.

[10]  L. Feitknecht,et al.  Hole drift mobility in μc-Si:H , 2001 .

[11]  M. Neukom,et al.  Determination of charge transport activation energy and injection barrier in organic semiconductor devices , 2017 .

[12]  M. Neukom,et al.  Reliable extraction of organic solar cell parameters by combining steady-state and transient techniques , 2012 .

[13]  W. D. Gill.  Drift mobilities in amorphous charge‐transfer complexes of trinitrofluorenone and poly‐n‐vinylcarbazole , 1972 .

[14]  J. C. Scott,et al.  Transient space-charge-limited current measurements of mobility in a luminescent polymer , 1999 .

[15]  R. Coehoorn,et al.  Effect of Gaussian disorder on the voltage dependence of the current density in sandwich-type devices based on organic semiconductors , 2008 .

[16]  Beat Ruhstaller,et al.  Quantitative analysis of pixel crosstalk in AMOLED displays , 2018 .

[17]  Beat Ruhstaller,et al.  Numerical simulation of charge transport in disordered organic semiconductor devices , 2010 .

[18]  Martin Neukom,et al.  Opto-electronic characterization of third-generation solar cells , 2018, Science and technology of advanced materials.

[19]  George G. Malliaras,et al.  Temperature- and field-dependent electron and hole mobilities in polymer light-emitting diodes , 1999 .

[20]  B. Ruhstaller,et al.  Modelling crosstalk through common semiconductor layers in AMOLED displays , 2018 .

[21]  R. Coehoorn,et al.  Monte Carlo study of charge transport in organic sandwich-type single-carrier devices: Effects of Coulomb interactions , 2011 .

[22]  Martin Neukom,et al.  Charge extraction with linearly increasing voltage: A numerical model for parameter extraction , 2011 .

[23]  S. Olthof,et al.  Single carrier devices with electrical doped layers for the characterization of charge-carrier transport in organic thin-films , 2010 .

[24]  Martin Pfeiffer,et al.  Doping of organic semiconductors , 2013 .

[25]  Paul Davids,et al.  Device model for single carrier organic diodes , 1997 .

[26]  Beat Ruhstaller,et al.  Numerical impedance analysis for organic semiconductors with exponential distribution of localized states , 2011 .

[27]  A. Kahn,et al.  Electronic structure and current injection in zinc phthalocyanine doped with tetrafluorotetracyanoquinodimethane: Interface versus bulk effects , 2002 .

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

[29]  James C. Blakesley,et al.  Towards reliable charge-mobility benchmark measurements for organic semiconductors , 2014 .

[30]  M. Szymański,et al.  Simplified transient space-charge-limited current measurements of mobility using transimpedance amplifier , 2013 .

[31]  H. Bässler.  Charge Transport in Disordered Organic Photoconductors a Monte Carlo Simulation Study , 1993 .

[32]  M. Neukom,et al.  The use of charge extraction by linearly increasing voltage in polar organic light-emitting diodes , 2017 .

[33]  H.C.F. Martens,et al.  Frequency-dependent electrical response of holes in poly(p- phenylene vinylene) , 1999 .

[34]  Denis Andrienko,et al.  Modeling of organic light emitting diodes: From molecular to device properties , 2015, International Conference on Numerical Simulation of Optoelectronic Devices.

[35]  Franky So,et al.  Bipolar charge transport, injection, and trapping studies in a model green-emitting polyfluorene copolymer , 2005 .

[36]  Tae-Hoon Yoon,et al.  Bulk and interface properties of molybdenum trioxide-doped hole transporting layer in organic light-emitting diodes , 2008 .

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