Solid State Electronics Effect of traps on the charge transport in semiconducting polymer PCDTBT (original) (raw)
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Influence of traps on charge transport in organic semiconductors
Solid-State Electronics, 2007
The effect of extrinsic traps on the charge transport in organic semiconductors has been investigated. An analytical model describing hopping transport with traps is formulated on the basis of percolation theory. The results show that the presence of a trap distribution with energy offset and width different from that of the intrinsic density of states does not change the basic phenomenology of hopping transport, as revealed by the temperature dependence of the conductivity at high temperature. However the traps may significantly affect the transport at low temperature. The relation between trap concentration and conductivity is discussed. The model predictions are in good agreement with experimental results.
IETI Transactions on Engineering Research and Practice, 2018
In this paper, new-improved carriers mobility model of OFET (Organic Field Effect Transistor) structures is presented. It is proposed to introduce two new factors: traps concentration ratio and electric field degradation factor, in carriers mobility model. The imact of OFET geometry is also considered. The above-mentioned model includes also carriers mobility dependence on temperature and electric field. Proposed model is incorporated in current-voltage characteristics of OFET.
Effect of Traps on Carrier Injection and Transport in Organic Field-effect Transistor
IEEJ Transactions on Electrical and Electronic Engineering, 2010
This study illustrates effect of traps on the charge injection and transport in the organic field-effect transistor (OFET). Here are included silicon nanoparticles (NPs) on a semiconductor-gate insulator interface, which work as trapping centers of charge carriers. Charge transport and injection phenomena are investigated by electrical measurements in presence of traps with designed densities. We find that OFETs with a low concentration of intrinsic carriers, such as a pentacene, are extremely sensitive to the internal electric fields. A significant threshold voltage shift due to trapped charge is observed, with a possibility to tune it by controlling the NP density. We demonstrate that the NP film can serve to design the amount of the accumulated charge in OFET and thus change the space-charge-limited conditions to the injection-limited conditions. A detailed analysis of pentacene OFET based on dielectric properties and the Maxwell-Wagner model reveals the internal electric field created by NPs. Additionally, the effect of NPs is discussed with respect to effective mobility, and its decrease is related to deceleration of carrier propagation by the trapping effect as well as low injection due to the increase of the carrier injection barrier by the internal field.
Trap-limited electrical properties of organic semiconductor devices
arXiv (Cornell University), 2023
We investigated the electrical properties of a unipolar organic device with traps that were intentionally inserted into a particular position in the device. Depending on their inserted position, the traps significantly alter the charge distribution and the resulting electric field as well as the charge transport behavior in the device. In particular, as the traps are situated closer to a charge-injection electrode, the band bending of a trap-containing organic layer occurs more strongly so that it effectively imposes a higher charge injection barrier. We propose an electrical model that fully accounts for the observed change in the electrical properties of the device with respect to the trap position.
Charge transport in organic and polymer thin-film transistors: recent issues
IEE Proceedings - Circuits, Devices and Systems, 2005
Interest in organic and polymer thin film transistors (OTFTs and PTFTs; hereafter both are called PTFTs) has grown rapidly in the last decade. However, the theory of charge transport in PTFTs lags experiments, so it is difficult to provide the required feedback to device designers and technologists. Therefore, the authors present an analysis of charge transport in PTFTs. It is based on extensive published theoretical and experimental material. The discussion includes examples exploring the trend in experimental results. It is noted that because of the similarity in device structures and current-voltage characteristics between PTFTs and inorganic metal-oxide-semiconductor (MOS) field-effect transistors (FETs), the MOS theory and model have been used extensively in analysing the properties of PTFTs. The MOS model has also been significantly modified to obtain agreement with experiments, and these modifications are discussed. However, recent experimental data from state-of-the-art PTFTs reveal that even the adapted MOS model cannot reliably describe the charge transport in PTFTs, because important PTFT properties such as charge injection or charge build-up result in unrealistic values for several physical parameters (e.g. trap concentrations or time constants) in the adapted MOS model. Therefore, the injection-drift limited model (IDLM) is introduced in this work in an attempt to bring the theory of charge transport and the experimental data closer. The IDLM incorporates the important charge transport phenomena in PTFTs -injection, drift and charge build-up. The paper concludes with a discussion of unsolved problems in charge transport in PTFTs.
Investigation of charge transport in organic polymer donor/acceptor photovoltaic materials
Journal of Modern Optics, 2014
π-conjugated organic semiconductors have long been used as either holes or electrons transport materials. Recently, ambipolar charge carrier transport in these materials have been reported in many investigations. In this paper, we report on the basis of experimental results that the organic semiconductor (donor/acceptor) materials can be as good electrons transporters as these materials are holes transporters. In our study, the solution-processed unipolar diodes based on organic materials P3HT, VOPCPhO, and their blends with PCBM have been fabricated. The I-V characteristics of these diodes have been analyzed in the space-charge-limited current regime. The values of the electron and hole mobilities for the materials were found in the range of 10 −4 -10 −5 cm 2 /Vs.
The Journal of Physical Chemistry B, 2004
We report structural and electrical transport properties of a family of π-stacking soluble organic semiconductors, N,N′-dialkyl-3,4,9,10-perylene tetracarboxylic diimides (alkylpentyl [1], octyl [2], and dodecyl [3]). The structures of evaporated polycrystalline films of 1-3 were studied using X-ray diffraction and atomic force microscopy. Films of 1-3 pack similarly with the direction of π-π overlap in the substrate plane. Organic thin film transistors (OTFTs) based on 1-3 deposited on SiO 2 gate dielectric showed linear regime electron mobilities of 0.1, 0.6, and 0.2 cm 2 /(V s), respectively, corrected for contact resistance. OTFTs of 2 had saturation electron mobilities as high as 1.7 cm 2 /(V s) with onto off current ratios of 10 7. Variable temperature measurements were used to examine the charge transport kinetics in the range 80-300 K and revealed (1) thermally activated electron mobilities with activation energies dependent on gate voltage and (2) the presence of well-defined isokinetic points, i.e., temperatures at which Arrhenius plots at different gate voltages intersect for a given film. Isokinetic points indicate a common charge transport mechanism and can be explained in terms of the multiple trapping and release (MTR) transport model. MTR assumes trap-limited band transport, and quantum chemical calculations were used to verify that delocalized transport is likely in 1-3; a conduction bandwidth of 0.58 eV was calculated for 1. Using MTR, the trap concentrations were estimated to be ∼10 12 cm-2 for deep traps, and ∼6 × 10 13 cm-2 for shallow traps. However, a nonmonotonic dependence of the electron mobility on gate voltage was also observed, which is not predicted by MTR and suggests that the transport mechanism is more complicated, perhaps due to the discrete layered structure of these materials. The high values for the electron mobility and onto off current ratio suggest that substituted perylene diimides represent a promising class of n-channel conductors for OTFTs.
Journal of Applied Physics, 2010
A significant difference between the transient electric field profiles of the pentacene organic field-effect transistors ͑OFETs͒ with SiO 2 and poly͑methyl-methacrylate͒ ͑PMMA͒ insulators was found by the time-resolved microscopic optical second-harmonic generation ͑TRM-SHG͒ experiment. The profile of former device was broad and changed smoothly, while the latter one had a sharp peak. Particularly, the peak of the transient electric field in SiO 2-insulated devices moved much faster than that in the PMMA-insulated one. Based on several experimental evidences and computational simulations, we proposed that these differences might arise from a higher trapped carrier density in the conductive channel on the PMMA insulator. Simple approaches were developed to evaluate the trap density and define dynamic carrier mobility in terms of the transient electric field measured by the TRM-SHG technique. This mobility quantitatively depicts that the transient hole transport in the OFET with the PMMA insulator is trap controlled.
Polymer International, 2019
Relevant organic thin-film transistor (OTFT) simulation software must account for the main specificities of organic semiconductors (OSC) in term of free carriers' density of states, transport mechanisms, and injection/collection properties from/to the device contacts. Among the parameters impacting the OTFT performance the carrier mobility is a key parameter. Usual methods to extract the mobility from current-voltage (()) measurements lead to obtained only an apparent, or effective, mobility. The value of the apparent mobility is different of the intrinsic channel organic semiconductor mobility. Despite this effective mobility actually determines most of a given device performance, therefore providing a very useful technology benchmark, it does not describe the intrinsic organic semiconductor material transport properties, and may even be misleading in the route to improve the OTFT fabrication process. To obtain a better understanding of the transport properties in OSCs using OTFT electrical characterization, implementing an appropriate physical mobility model in an OTFT () simulation software is a good way. The present paper gives a review of the carrier mobility models which can be implemented in OTFT simulation software. The review is restricted to the analytical and semi