Benjamin J. Rancatore

Nanostructured Organic Semiconductors via Directed Supramolecular Assembly

Organic small molecule semiconductors have many advantages over their polymer analogues. However, to fabricate organic semiconductor-based devices using solution processing, it is requisite to eliminate dewetting to ensure film uniformity and desirable to assemble nanoscopic features with tailored macroscopic alignment without compromising their electronic properties. To this end, we present a modular supramolecular approach. A quaterthiophene organic semiconductor is attached to the side chains of poly(4-vinylpyridine) via noncovalent hydrogen bonds to form supramolecular assemblies that act as p-type semiconductors in field-effect transistors. In thin films, the quaterthiophenes can be readily assembled into microdomains, tens of nanometers in size, oriented normal to the surface. The supramolecules exhibited the same field-effect mobilities as that of the quaterthiophene alone (10(-4) cm(2)/(V.s)). Since the organic semiconductors can be readily substituted, this modular supramolecular approach is a viable method for the fabrication of functional, nanostructured organic semiconductor films using solution processing.

PbS Nanoparticles Capped with Tetrathiafulvalenetetracarboxylate: Utilizing Energy Level Alignment for Efficient Carrier Transport

We fabricate a field-effect transistor by covalently functionalizing PbS nanoparticles with tetrathiafulvalenetetracarboxylate. Following experimental results from cyclic voltammetry and ambient-pressure X-ray photoelectron spectroscopy, we postulate a near-resonant alignment of the PbS 1Sh state and the organic HOMO, which is confirmed by atomistic calculations. Considering the large width of interparticle spacing, we observe an abnormally high field-effect hole mobility, which we attribute to the postulated resonance. In contrast to nanoparticle devices coupled through common short-chained ligands, our system maintains a large degree of macroscopic order as revealed by X-ray scattering. This provides a different approach to the design of hybrid organic-inorganic nanomaterials, circumvents the problem of phase segregation, and holds for versatile ways to design ordered, coupled nanoparticle thin films.

Modular small-molecule directed nanoparticle assembly

We demonstrate a simple and versatile approach to produce hierarchical assemblies of nanoparticles by combining block copolymers and small molecules. Directed nanoparticle assemblies can be achieved with a variety of nanoparticles and small molecules without modification of the nanoparticle ligands. This novel approach opens up new routes toward the fabrication of nanoparticle-based functional devices using a “Bottom-Up” approach.