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Peter Hadley

Publications and source records attributed to Peter Hadley.

6 recordsLinked to original sources
PubMed2004

Correlation between crystal structure and mobility in organic field-effect transistors based on single crystals of tetrathiafulvalene derivatives.

Recently, it was reported that crystals of the organic material dithiophene-tetrathiafulvalene (DT-TTF) have a high field-effect charge carrier mobility of 1.4 cm(2)/(V x s). These crystals were formed by a simple drop-casting method, making this material interesting to investigate for possible applications in low-cost electronics. Here, organic single-crystal field-effect transistors based on materials related to DT-TTF are presented and a clear correlation between the crystal structure and the electrical characteristics is observed. The observed relationship between the mobilities in the different crystal structures is strongly corroborated by calculations of both the molecular reorganization energies and the maximum intermolecular transfer integrals. The most suitable materials described here exhibit mobilities that are among the highest reported for organic field-effect transistors and that are the highest reported for solution-processed materials.

Journal Article↗
PubMed2004

Importance of intermolecular interactions in assessing hopping mobilities in organic field effect transistors: pentacene versus dithiophene-tetrathiafulvalene.

We report on a computational study to understand the high mobility found in dithiophene-tetrathiafulvalene (DT-TTF) transistors, with respect to that known for pentacene, using an extended measure of the reorganization energy (lambdareorg). We demonstrate the high importance of considering intermolecular interactions to assess hole-hopping mobilities. We find that due to the steric, polarizable environment and the structural changes induced by local intermolecular charge delocalization, the calculated lambdareorg for DT-TTF decreases from 0.574 eV in the isolated molecule to 0.042 eV in the crystal embedded molecule, which is of the same order of the previously reported value found for the isolated pentacene molecule, 0.098 eV.

Journal Article↗
PubMed2004

High mobility of dithiophene-tetrathiafulvalene single-crystal organic field effect transistors.

Single-crystal field effect transistors of the organic semiconductor dithiophene-tetrathiafulvalene (DT-TTF) were prepared by drop casting. Long, thin crystals connected two microfabricated gold electrodes, and a silicon substrate was used as a back gate. The highest hole mobility observed was 1.4 cm2/Vs, which is the highest reported for an organic semiconductor not based on pentacene. A high ON/OFF ratio of at least 7 x 105 was obtained for this device.

Journal Article↗
PubMed2003

Electrical transport study of phenylene-based pi-conjugated molecules in a three-terminal geometry.

We fabricated three-terminal devices with conjugated molecules. Two different device layouts were used to measure both very short molecules (with one or two benzene rings) and relatively long ones (as long as 8 nm). To achieve an optimum gate effect, we used aluminum gates covered with a very thin native oxide layer. Molecules with thiol end groups were positioned between the source and drain electrodes by self-assembly. The device yield was low for short molecules, most likely due to defects in the self-assembled monolayers. Most of the devices made with short molecules did not show any gate effect at all; a small gate effect was only observed in two samples made with 1,3-benzenedithiol. Some devices showed clear negative differential conductance peaks. In some devices made with long molecules, we observed a small change of conductance with gate voltage.

Benzene Derivatives↗