Effects of Gaussian Disorder on Charge‐Carrier Transport and Recombination in Organic Semiconductors

Coehoorn, R.; Bobbert, Peter A.

doi:10.1002/9783527654949.ch6

Cited by 13 publications

(23 citation statements)

References 109 publications

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“…This type of MST behavior has also been reported for Er:ZnO, (Er, Yb)‐doped ZnO . Also, according to Miller‐Abrahams equation, the hopping frequency varies inversely with hopping distance, further the probability of bigger jump is higher at elevated temperature due to thermal excitations. In the pristine sample, the resistivity was higher at lower temperatures due to non‐availability of hopping sites near each other.…”

Section: Electrical Propertiessupporting

confidence: 72%

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

Arora

Kumar²,

Kaur

et al. 2018

J Am Ceram Soc

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Compounds of undoped and samarium (Sm) doped ZnO have been prepared by standard solid‐state reaction method. X‐ray diffraction (XRD), Williamson‐Hall (W‐H) analysis, Transmission Electron Microscopy (TEM), temperature‐dependent electrical and dielectric studies have been done to characterize these materials. Inclusion of Sm as dopant in hexagonal wurtzite ZnO changes the lattice parameters to a small extent with some Sm aggregation at higher concentration. Also, the mean particle sizes of ZnO:Sm compounds showed an inter‐correlation with the Scherrer method, W‐H analysis as well as with TEM results. The electrical resistivity depicts an exponential decay and metal‐semiconductor transition (MST) at ~300 K for the pristine sample whereas there is large decrement in the resistivity with Sm doping. The analysis of σac of ZnO suggests that the power law is obeyed and indicated an increase in the ac conductivity with Sm content. The mechanism behind this type of conductivity is elucidated by small polaron tunneling (SPT) model of conductivity. The dependence of ln dc on the temperature inverse shows that the traps of electrons are thermally activated such that low and high temperature activation energies confirm the presence of vacancies and interstitials of both O and Zn ions. Thus, a high value of dielectric constant makes these materials suitable for high frequency and charge storage device applications.

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Section: Electrical Propertiessupporting

confidence: 72%

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

Arora

Kumar²,

Kaur

et al. 2018

J Am Ceram Soc

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“…Such a scenario would be similar to host/guest systems in disordered organic semiconductors. 57 With increasing gate voltage, the number of SWNTs that contribute to the transport increases and thus the effective network density changes. This effect further complicates field-effect mobility calculations for mixed SWNT networks.…”

Section: Resultsmentioning

confidence: 99%

Understanding Charge Transport in Mixed Networks of Semiconducting Carbon Nanotubes

Rother

Schießl

Zakharko

et al. 2016

ACS Appl. Mater. Interfaces

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The ability to select and enrich semiconducting single-walled carbon nanotubes (SWNT) with high purity has led to a fast rise of solution-processed nanotube network field-effect transistors (FETs) with high carrier mobilities and on/off current ratios. However, it remains an open question whether it is best to use a network of only one nanotube species (monochiral) or whether a mix of purely semiconducting nanotubes but with different bandgaps is sufficient for high performance FETs. For a range of different polymer-sorted semiconducting SWNT networks, we demonstrate that a very small amount of narrow bandgap nanotubes within a dense network of large bandgap nanotubes can dominate the transport and thus severely limit on-currents and effective carrier mobility. Using gate-voltage-dependent electroluminescence, we spatially and spectrally reveal preferential charge transport that does not depend on nominal network density but on the energy level distribution within the network and carrier density. On the basis of these results, we outline rational guidelines for the use of mixed SWNT networks to obtain high performance FETs while reducing the cost for purification.

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“…Actually, the experimental critical concentration at which the mobility starts to show density–dependence can only be explained assuming a DOS shape very close to the Gaussian one 19 . In general terms, it is possible that a single energy scale cannot effectively describe the real DOS (due to the superposition of inhomogeneously broadened, electronically inequivalent molecular states) 18 , as we actually verified for a recently synthesized n-type polymer 20 that required two Gaussians in order to satisfactorily fit CV curves. In such case, to our knowledge, neither the EGDM nor any other analytical model is able to accurately describe carrier transport.…”

Section: Discussionmentioning

confidence: 54%

Simultaneous Extraction of Density of States Width, Carrier Mobility and Injection Barriers in Organic Semiconductors

Africa

Falco

Maddalena

et al. 2017

Sci Rep

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The predictive accuracy of state-of-the-art continuum models for charge transport in organic semiconductors is highly dependent on the accurate tuning of a set of parameters whose values cannot be effectively estimated either by direct measurements or by first principles. Fitting the complete set of model parameters at once to experimental data requires to set up extremely complex multi-objective optimization problems whose solution is, on the one hand, overwhelmingly computationally expensive and, on the other, it provides no guarantee of the physical soundness of the value obtained for each individual parameter. In the present study we present a step-by-step procedure that enables to determine the most relevant model parameters, namely the density of states width, the carrier mobility and the injection barrier height, by fitting experimental data from a sequence of relatively simple and inexpensive measurements to suitably devised numerical simulations. At each step of the proposed procedure only one parameter value is sought for, thus highly simplifying the numerical fitting and enhancing its robustness, reliability and accuracy. As a case study we consider a prototypical n-type organic polymer. A very satisfactory fitting of experimental measurements is obtained, and physically meaningful values for the aforementioned parameters are extracted.Organic semiconductors are an outstanding candidate for becoming the material platform for the development of large-area, low cost, flexible electronics 1 . Since they can be processed from solution, they can be formulated as functional inks and deposited by means of printing techniques adapted from graphical arts (ink-jet, screen printing, spray coating, flexography to cite but a few) 2 . Their electronic performance has been constantly improving over the years leading to devices which compare well to, or even outperform, those based on amorphous silicon. Despite this technological progress, many fundamental questions are still debated and there is a strong need for simple yet reliable approaches to extract physical parameters from experimental measurements 3 .Recently we have shown that, by fitting Capacitance-Voltage (CV) measurements of Metal-InsulatorSemiconductor (MIS) capacitors, it is possible to extract the width of the Density of States (DOS) -assuming it is a superposition of Gaussian functions -exploiting the sensitivity of CV curves to the semiconductor disorder degree 4, 5 . By operating MIS capacitors at suitably low frequency, quasi-equilibrium is ensured which implies that simulations can be performed in the static regime and that phenomena specifically related to carrier transport are negligible in order to fit experimental measurements, which leads to advantages in terms of both computational cost and accuracy. In addition, the DOS extraction is disentangled from carrier transport properties, which makes the fitting procedure substantially simpler and more robust.If a DOS consisting of a single Gaussian provides a reasonable fit, the carrier mobility ...

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Effects of Gaussian Disorder on Charge‐Carrier Transport and Recombination in Organic Semiconductors

Cited by 13 publications

References 109 publications

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

Understanding Charge Transport in Mixed Networks of Semiconducting Carbon Nanotubes

Simultaneous Extraction of Density of States Width, Carrier Mobility and Injection Barriers in Organic Semiconductors

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