Showing papers by "Sean E. Shaheen published in 2003"

Hybrid organic-inorganic photoconductive diode

Abstract: A hybrid organic-inorganic diode has been fabricated by hot-wire chemical vapor deposition of low process temperature (<140 °C) hydrogenated amorphous silicon (a-Si:H) onto a spin-coated layer of poly(N-vinylcarbazole) (PVK). The hybrid device was found to be a photoconductive diode with a high photosensitivity of near 700, a high photogain of over 100, and a response time of 500 μs. The high photosensitivity of the a-Si:H intrinsic layer and the large barrier for carrier injection at the PVK/a-Si:H interface are responsible for the good performance.

Polymer Based Nanostructured Donor-Acceptor Heterojunction Photovoltaic Devices

Abstract: Bulk heterojunction photovoltaic devices based on blends of conjugated polymers and fullerenes have achieved efficiencies of 3.5% under AM1.5 illumination. This is a result of efficient exciton dissociation at donor–acceptor interfaces. However, the intimate blending of the electron and hole transporting species leads to detrimental charge carrier recombination in the bulk of these devices. We are investigating a solution to this problem by fabricating nanostructured oxide–conjugated polymer composite structures. Porous SnO2 films with pore diameters of ~100 nm have been fabricated. Intercalation of polymers into the pores by adsorption from solution yielded structures with approximately 75% of the free volume filled with polymer. The resulting composite structures are promising candidates for developing polymer-based solar cells with short carrier-to-electrode path lengths while retaining high optical absorption, thus leading to increased efficiencies. Additionally, a carboxylic acid fullerene derivative was shown to bind to the SnO2 surface, a necessary step in creating a nanostructured electron-accepting surface.