Charge Transport Mechanism in Molecularly Doped Polymers

Di-p-tolyl-p-nitrophenylamine (DTNA) is a highly polar donor molecule with a dipole moment of 5.78 D. Hole mobilities have been measured in DTNA doped poly(styrene) over a range of fields, temperatures, and DTNA concentrations. The results are described within the framework of a formalism based on disorder, due to Bassler and coworkers. In the disorder formalism, it is assumed that charge propagation occurs by hopping through a manifold of localized states with superimposed energetic and positional disorder. A key parameter of the formalism is the energy width of the hopping site manifold. For DTNA doped poly(styrene), the width is approximately 0.15 eV and independent of the intersite distance, or DTNA concentration. The width is described by a model based on dipolar disorder. The model is premised on the assumption that the width is determined by a dipolar component due to the DTNA molecule and a van der Waals component. The interpretation of the experimental results leads to the conclusion that the van der Waals component increases with increasing intersite distance.

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Charge-carrier transport in smectic mesophases of biphenyls

Ohno

Haruyama

Kurotaki

et al. 2007

Journal of Applied Physics

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The charge-transport properties of ω,ω′-alkylalkoxylbiphenyls, one of the simplest calamitic (rodlike) liquid crystals exhibiting smectic mesophases, were investigated using the time-of-flight experiments. A mobility of ∼10−3 cm2∕V s was determined for holes in both smectic B (SmB) and smectic E (SmE) phases. This high electronic mobility, comparable to the highest mobilities in amorphous organic semiconductors, indicates that the self-organization of such simple molecules including small aromatic compounds is quite effective in enhancing the charge transport in organic materials. The mobilities of both smectic mesophases, however, depend on temperatures, which is not the case for other typical smectic liquid crystals reported previously. Interestingly, the mobility in the SmE phase exhibits a Poole–Frenkel type of field dependence. Detailed experimental studies have shown that this field dependence is not due to the trapping effect of carriers caused by chemical contaminants or structural defects such as domain boundaries and dislocation, but arises from the widely distributed density of states with a distribution width of 0.11–0.13 eV for the SmE phase, as estimated based on a two-dimensional Gaussian disorder model. The phase-specific carrier transport in biphenyls may provide us with unique insights leading to a more complete understanding of the charge carrier transport in the mesophase materials.

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Charge Transport Mechanism in Molecularly Doped Polymers

Cited by 4 publications

References 10 publications

The role of disorder on charge transport in molecularly doped polymers and related materials

The role of disorder on charge transport in molecularly doped polymers and related materials

Hole Transport in Di‐p‐Tolyl‐p‐Nitrophenylamine Doped Poly(styrene)

Charge-carrier transport in smectic mesophases of biphenyls

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