Charge Carrier Mobility In Poly Research Articles

Charge Carrier Mobility in Poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine Composites with Electron Acceptor Molecules.

Polymer composites based on poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (poly-TPD) with PCBM and copper(II) pyropheophorbide derivative (Cu-PP) were developed. In thin films of the poly-TPD and Cu-PP composites, the charge carrier mobility was investigated for the first time. In the ternary poly-TPD:PCBM:Cu-PP composite, the electron and hole mobilities are the most balanced compared to binary composites and the photoconductivity is enhanced due to the sensitization by Cu-PP in blue and red spectral ranges. The new composites are promising for use in the development of photodetectors.

Dopant induced anomalous field dependent mobility behavior of poly(3-octylthiophene) devices

Temperature dependent DC current-voltage (I-V) down to 50 K and field-dependent AC impedance measurements were carried out to study the electric field and temperature dependence of charge carrier mobility in Poly(3-octylthiophene) based metal/polymer/metal device structures of different charge carrier concentrations. In highly doped device, a negative field-dependent mobility (NFDM) which vanishes below 150 K was observed whereas a positive field-dependent mobility (PFDM) was observed in moderately doped devices. The observed NFDM is attributed to the low energetic disorder and high positional disorder in the highly doped devices. With further lowering of carrier concentration, charge carrier mobility first decreases with the increase in applied field attaining a minimum value and then increases with the applied field. At higher temperatures (T>150K), all the three devices show thermally-activated process and activation energy increases with lowering the charge carrier concentrations indicating that doping level plays important role in thermally activated transport mechanism. However, in lower temperature (T<100K), activation energy is almost independent of doping level suggesting that injected carrier plays an important role in the lower temperature region. Data from AC impedance measurement also supports the field-dependent mobility model of conduction mechanism in the devices. Analysis of the AC impedance data of the three devices reveals that the equivalent circuit of highly and moderately doped devices is different from that of the low carrier concentration device. The presence of highly energetic disorder in low carrier concentration devices is also confirmed from AC impedance analysis.

Charge carrier mobility in poly[methyl(phenyl)silylene] studied by time-resolved terahertz spectroscopy and molecular modelling

Time-resolved terahertz spectroscopy and combination of quantum chemistry modeling and molecular dynamics simulations were used for the determination of charge carrier mobility in poly[methyl(phenyl)silylene]. Using time-resolved THz spectroscopy we established the on-chain charge carrier drift mobility in PMPSi as 0.02 cm(2) V(-1) s(-1). This value is low due to the formation of polarons: the hole is self-trapped in a potential formed by local chain distortion and the transient THz conductivity spectra show signatures of its oscillations within this potential well. This view is supported by the agreement between experimental and calculated values of the on-chain charge carrier mobility.

Polaronic transport in polysilanes

Analytical theory based on the effective medium approach is used to explain electric field dependences of charge carrier mobility in poly[methyl(phenyl)silylene]. It is shown that the charge transport can be described by a small polaron movement in the presence of correlated energetic disorder. Polaron binding energy is the main part of the activation energy of the mobility.

Model of the influence of energetic disorder on inter‐chain charge carrier mobility in poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene

AbstractThe theoretical model of the inter‐chain charge carrier mobility in poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene] (MEH–PPV) doped with polar additive is put forward. The polymer chain states of a charge carrier were calculated by means of diagonalization of a tight‐binding Hamiltonian, which includes disorder in both the local energies and transfer integrals. Consequently, the inter‐chain charge carrier transport is taking place on a spatially and energetically disordered medium. Because it is believed that the additive does not significantly influence the polymer supramolecular structure, the polymer conformations were simplified as much as possible. On the other hand, the energetic disorder is rigorously described. The transfer rates between the polymer chains were determined using the quasi‐classical Marcus theory. The model considered the following steps of the charge carrier transport: the charge carrier hops to a given polymer chain. Then, the charge carrier thermalizes to the Boltzmann distribution over all its possible states on this chain. After that, the charge carrier hops to any possible state on one of the four nearest neighboring chains. The results showed that the inter‐chain charge carrier mobility is very strongly dependent on the degree of the energetic disorder. If the energetic disorder is doubled from 0.09 to 0.18 eV, the mobility decreases by two or three orders of magnitude. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Electrodeless Determination of Charge Carrier Mobility in Poly(3-hexylthiophene) Films Incorporating Perylenediimide as Photoconductivity Sensitizer and Spectroscopic Probe

The charge carrier mobility and its generation efficiency in regioregular and regiorandom poly(3-hexylthiophene) (P3HT) films upon exposure to light pulses are studied by flash-photolysis time-resolved microwave conductivity and transient absorption spectroscopy. For the full experimental determination of alternating current mobility without electrodes, we incorporated a perylenecarboxydiimide (PDI) derivative into the films not only to increase the photoconductivity but also estimate the quantum efficiency of charge generation by kinetic tracing of PDI radical anions. We discuss the mobility, quantum efficiency, decay of charge carriers, and film morphology observed by an X-ray diffraction and an atomic force microscope with various PDI concentrations. It is found that the three-dimensional mobility mainly attributed to the positive charges on regioregular P3HT is decreased from 0.12 to 0.070 cm2/Vs by addition of PDI which disturbs the intermolecular π-stacking, while that on regiorandom P3HT shows an almost constant value of 0.006 cm2/Vs. The quantum efficiency in regioregular P3HT reveals a peak at 6 mol % PDI for 355-nm excitation. The reason for the appearance of the peak is examined by changing excitation wavelength and inspecting the steady-state absorption and fluorescence spectra. The methodology and findings obtained by utilizing the additive as both an acceptor and a probe is proved to be useful for the investigations on optoelectronic properties of wide varieties of organic semiconductors.

Influence of dipolar species on charge transport in poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene

AbstractA theoretical study and experimental evidence for a decrease of the charge carrier mobility in poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene] (MEH‐PPV) under the influence of dipolar species are presented in this paper. The presence of polar species in the vicinity of an MEH‐PPV chain modifies the on‐chain site energies and consequently, due to random mutual positions and orientations, increases the width of the energy distribution of the chain transport states. The influence of energetic disorder of these states on the charge carrier mobility was modeled by means of the Monte Carlo method, based on a numerical solution of the time‐dependent Schrödinger equation in the tight‐binding approximation. It was shown that the increasing disorder destroys the resonance between charge carrier energies on adjacent sites and, therefore, limits the diffusive charge carrier motion. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Charge carrier mobility in poly(p-phenylenevinylene) studied by the time-of-flight technique

The charge carrier transport in poly(p-phenylenevinylene) (PPV) is investigated by the time-of-flight technique. Mobilities of positive carriers in PPV are determined and the dispersive character of transport is established. The dispersion parameters are analyzed in the frame of a multiple trapping model. The drift mobility of the positive carriers is in the range of 10-5 cm2/V at room temperature for an electric field of 105 V/cm and increases with increasing field and temperature. The mobility shows thermally activated behavior with an activation energy of about 0.75 eV at zero field. It is shown that the experimental results can be interpreted by polaron transport.