Charge Mobilities in Organic Semiconducting Materials Determined by Pulse-Radiolysis Time-Resolved Microwave Conductivity:  π-Bond-Conjugated Polymers versus π−π-Stacked Discotics

Abstract

A review is given of the one-dimensional, intrachain and intracolumnar, charge mobilities, Σµ 1D , determined for π-bond-conjugated polymeric and for π-π-stacked columnar discotic materials using the pulse-radiolysis time-resolved microwave conductivity technique. The largest values, on the order of 10 cm 2 /(V s), are found for single-crystal polydiacetylenes polymerized either thermally or with low doses of radiation. Much lower values of Σµ 1D , covering the range from 0.009 to 0.125 cm 2 /(V s), are found for solution-synthesized conjugated polymers for which six different backbone structures have been investigated. This is attributed mainly to their complex morphology and the resulting static disorder in the backbone structure. The highest mobilities for this class of material, ca. 0.1 cm 2 /(V s), are found for liquid crystalline derivatives of polyfluorene and poly(phenylenevinylene). Larger mobilities are found for discotic materials, with maximum values close to 1 cm 2 /(V s) in both the crystalline solid and liquid crystalline phases. This is attributed to their self-organizing nature and hence higher degree of structural order, which compensates for the weaker electronic coupling between monomeric units in the discotics compared with the covalently bonded conjugated polymers.

Photoproduction of Proton Gradients with π-Stacked Fluorophore Scaffolds in Lipid Bilayers

“…The construction of complex and multifunctional p-architecture is difficult because of the poor directionality of p,p-interactions (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). Apart from a central role in oligonucleotide chemistry and biology (18), cofacial p-stack architecture contributes very little to electron transfer in biological (1-3) and synthetic (4-7) photosystems, not to speak of the structure of biological or synthetic ion channels or pores (19).…”

A Room‐Temperature Liquid‐Crystalline Phase with Crystalline π Stacks

“…For example, a sudden increase in charge-carrier mobility is always observed when a DCLC phase becomes ordered into a crystalline phase with a p stack. [3] Therefore, a LC phase with crystalline p stacks would be ideal as it combines the maximal charge-carrier mobility of crystalline p stacks with the unique processability of LC materials. Here we report the molecular design, synthesis, and structural characterization of the first such LC material.…”

Synthetic Multifunctional Nanoarchitecture in Lipid Bilayers: Ion Channels, Sensors, and Photosystems

“…Unidirectional charge mobility in -stacks can be as good as in conjugated polymers, with precise self-organization, sample conditions and sample history being as critical as monomer structure. 99,100 Charge mobilities in advanced discotic liquid crystalline -stacks, for example, are with up to 1 cm 2 V À1 s À1 clearly beyond the reported %0:1 cm 2 V À1 s À1 for solution-synthesized conjugated polymers such as liquid-crystalline polyfluorene and poly-(phenylenevinylene). Compared to conjugated polymers, selforganization in refined coronene, porphyrin, or phthalocyanine -stack architecture can overcompensate the weaker electronic coupling between monomer units.…”