Martin Glodde

Self-organization of supramolecular helical dendrimers into complex electronic materials

The discovery of electrically conducting organic crystals and polymers has widened the range of potential optoelectronic materials, provided these exhibit sufficiently high charge carrier mobilities and are easy to make and process. Organic single crystals have high charge carrier mobilities but are usually impractical, whereas polymers have good processability but low mobilities. Liquid crystals exhibit mobilities approaching those of single crystals and are suitable for applications, but demanding fabrication and processing methods limit their use. Here we show that the self-assembly of fluorinated tapered dendrons can drive the formation of supramolecular liquid crystals with promising optoelectronic properties from a wide range of organic materials. We find that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores π-stacks of donors, acceptors or donor–acceptor complexes exhibiting high charge carrier mobilities. When we use functionalized dendrons and amorphous polymers carrying compatible side groups, these co-assemble so that the polymer is incorporated in the centre of the columns through donor–acceptor interactions and exhibits enhanced charge carrier mobilities. We anticipate that this simple and versatile strategy for producing conductive π-stacks of aromatic groups, surrounded by helical dendrons, will lead to a new class of supramolecular materials suitable for electronic and optoelectronic applications.

Erratum: Self-organization of supramolecular helical dendrimers into complex electronic materials (Nature (2002) 419 (384-387))

This corrects the article DOI: nature01072

Electronic transport in self-organizing columnar phases

This paper presents measurements of time-of-flight charge carrier mobility and thermal optical polarized microscopy on a new class of columnar liquid crystals (LC) self-organized into hexagonal columnar mesophase self-assembled form functionalized dendrons. We discuss the temperature and electric field-independent high hole mobility of 1-3.5×10-3 cm2/Vs. The anomalous temperature behavior of the mobility is consistent with polaron transport mechanisms. Studies of time-of-flight transients, which reveal evidence for dynamic defects with lifetimes in the range of 10-6 s, are presented as aspects of charge gneeration and recombination kinetics. We demonstrate the enhancement of electron transport in acene-based dendron LCs by dopign wtih TNF-based dendron molecules.