Articles you may be interested inAnalysis of metal-oxide-based charge generation layers used in stacked organic light-emitting diodes This paper presents a unified model for charge injection and transport in organic or polymeric diodes. A special focus is placed on charge injection from the contacts, using existing models such as thermionic emission and tunnel injection. These are combined to produce a compact model that includes effects associated with oxidation/reduction reactions at the electrodes. Charges are formed at the electrodes by oxidation or reduction in a process governed by the Nernst equation, and these charges modulate the injection barrier. A current-voltage relationship for organic or polymeric diodes that incorporates these injection phenomena, as well as the charge transport by the drift mechanism, is presented and discussed. The voltage ranges in which these effects are dominant are estimated. Finally, the resulting current-voltage and current-temperature relations are used to explain published experimental data.
A compact model has been employed in organic thin film transistors (OTFTs) to study the electrical characteristics of the contacts, which are formed between the organic layer and source/drain electrodes of the OTFT. The model shows the importance of interrelating different physical phenomena: charge injection, redox reactions at the interface, and charge drift in the organic semiconductor. The model reproduces and explains several features that have been reported for current-voltage curves, ID-VC, at the contacts of OTFTs. The ID-VC curves are extracted from the experimental output characteristics by two techniques. One technique uses a set of transistors with different channel lengths and a simultaneous extraction of the ID-VC curve and the mobility of carriers in the channel of the transistor. When a set of transistors with different channel lengths is not available, we propose an iterative method for the simultaneous extraction of the ID-VC curve and the mobility by changing the gate bias voltages.
This paper presents a procedure to evaluate the charge density in the low conductivity regions between the metal and the accumulated intrinsic channel of an organic thin film transistor (OTFT). This charge links different physical mechanisms in the contacts of OTFTs. The charge density is evaluated in transistors with different metal-organic barriers to study its dependence with the voltage, temperature and the materials forming the contact.
Recombination centers in thin asymmetrical p-n junctions were analyzed in the context of capacitance transient experiments. The combined effect of the thin low-doped region of the junction and the nonzero value of the occupation factor of the recombination center in the depletion layer caused electrons and holes to be simultaneously released from different parts of this layer during an emission transient. The need to introduce modifications in the analytical expressions that determine the parameters of these centers by capacitance transient spectroscopy is demonstrated. A correction formula to determine concentrations of electron or hole traps or recombination centers is proposed.
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