Rectifying junctions of tin oxide and poly(3-hexylthiophene) nanofibers fabricated via electrospinning Abstract Abstract: A fast, simple, and inexpensive method to fabricate in air, p-n diodes using electrospun tin oxide nanoribbons and regioregular poly(3-hexylthiophene) nanofibers is described. In addition to being a rectifier under ambient illumination or in the dark, the advantage of our design is the complete exposure of the rectifying nanojunction to the surrounding environment, making them attractive candidates in the potential fabrication of low power consumption diodes and sensors. The diode characteristics were analyzed using the standard diode equation and its use as a UV light sensor was examined.

Interfaces play an important role in bulk heterojunction organic/inorganic hybrid photovoltaic devices, but directly probing the interface in order to improve device characteristics is exceedingly difficult. We report on a method to form core-shell inorganic nanowire-polymer hybrids of a conducting polymer, poly(3-hexlthiophene-2,5-diyl) (P3HT), and a semiconducting nanowire, cadmium sulfide (CdS), using solution processing to create the polymer shell around the nanowire in order to study the polymer-nanowire interface directly without interference from bulk effects. We have used the rod-coil transition (chromism) in P3HT to seed and enhance the crystallinity at the polymer-nanowire interface. We have shown that creating more order within the P3HT main chain, by controlling the temperature and the solvent quality, can increase the extent of polymer crystallinity present at the polymer-nanowire interface. We believe using the rod-coil transition to create more order in P3HT and the resulting polymer-nanowire interface will provide a facile pathway for designing future organic-inorganic photovoltaic devices.

Increasing performance in organic/inorganic bulk heterojunctions hybrid photovoltaic systems hinges not only on the structure of the inorganic component but also on the morphology of the polymeric component. Changing the morphology of the organic component is a facile way of changing the morphology of the interface between the inorganic and organic components in the bulk heterojunction system. Engineering this interface to more efficiently split photogenerated excitons and transport these carriers to electrodes can increase the efficiency of photovoltaic devices. In this report, we investigate the effect of solvent quality on the morphology of the poly(3-hexylthiophene)-2,5-diyl (P3HT) polymer-semiconductor interface (solvatochromism). We have found that creating more order within the P3HT main chain in solution and prior to deposition has a profound effect on the nature of the P3HT-CdS nanowire interface. Solvents with a larger difference in solubility parameter, Δδ, relative to P3HT, such as methanol and isopropanol, create larger rod domains in the P3HT main chain and result in larger domains of crystalline P3HT at the interface. Solvents with similar solubility parameters as P3HT, such as pyridine and hexanol, create relatively shorter rod domains in the main chain and, as a result, nanohybrids with reduced crystallinity. The results of this paper further cement the importance of manipulating the rod-coil transition in the conducting polymers such as P3HT to improve the crystallinity at the polymer-semiconductor interface that can easily be scaled up to improve the efficiency of bulk heterojunction photovoltatic systems.

Electrospinning has been thought of as an effective, low cost technique for producing nanofibers for use in gas sensor applications with nanofibers of tin oxide showing particular promise in this area. Critical to the success of tin oxide in these applications are nanowires with a rutile phase structure and well defined current-voltage characteristics which requires controlled fiber diameters. This paper reports on the characterization of the pre and post sintered fibers deposited via electrospinning of two different tin precursor chemicals, dimethyl dineodecanoate tin and dimethyl dichloro tin, both spun within a polyethylene oxide / chloroform binder system. Both tin precursor systems were evaluated at different concentration levels to investigate morphological changes due to concentration. Mats of fibers were spun on silicon wafers and sintered at 600°C for 2 hours. Morphology was characterized by optical microscope while chemical composition was determined via Raman spectrometry. Fibers of dimethyl dineodecanoate tin were found be ∼30μm in diameter and to have considerable component separation upon deposition. After sintering, SnO2 islands were found but there was no fiber appearance. Fibers of dimethyl dichloro tin were found to be ∼10μm in diameter and lacked the component separation seen in the other tin precursor system with some SnO2 domains found directly inline with initial fiber deposition. Comparison of results from both systems shows that the interaction of the polymer and tin precursor is of paramount importance for development of micro- or nanosized ceramic wires deposited by electrospinning.