We report a hybrid photovoltaic cell where PbSe nanocrystals were used to sensitize the conjugated polymer into the infrared. The device exhibited an incident monochromatic photon to current conversion efficiency of 1.3% at λ=805nm. Under 1 sun AM 1.5 illumination, the infrared response (780nm<λ<1600nm) of the embedded nanocrystals contributes to 33% of the overall photocurrent of the photovoltaic cell. The observed intensity dependences of the photocurrents have revealed the pseudomonomolecular recombination kinetics in the nanocrystal quantum dot polymer composite, indicating that the efficiency of the hybrid photovoltaic cells can be enhanced by reducing the potential barriers due to the ligand molecules at the surfaces of nanocrystals.

Possibilities of manipulating the Rabi frequency and luminescence rate from degenerate-level systems as well as the velocity of self-induced transparency of multi-level media are studied using a unitary transformation. The Rabi frequency and luminescence rate of an electronic system whose ground level is degenerate and coupled to a resonant mode are found to depend on the level of the degeneracy. The velocity of multi-mode optical solitons in a multi-level medium is found to be influenced by the number of propagating resonant pulses. Physical realizations of relevant systems are proposed.

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Abnormal rectifying behavior has been observed in molybdenum/silicon Schottky barrier diodes produced by ion-beam sputter deposition of Mo on single-crystal Si. Rectifying, rather than ohmic contacts are obtained on p-type Si, while ohmic behavior is seen on n-type Si. These results are contrary to the usual results reported in the literature, and are shown to be caused by ion-beam surface damage of Si. The damage does not simply cause a surface layer of high-recombination velocity, but rather tends to bend the Si band edges downwards, irrespective of the Si conductivity type.

A unipolar accumulation-type field effect transistor (FET) is proposed, fabricated, and characterized. The device, which uses a single doping type and Ohmic contacts, relies on the nanoscale to force the only possible source-drain path to pass through an accumulated (on state) or depleted (off state) region. The transistor is demonstrated using silicon nanowires (SiNWs) grown on glass with our nanochannel-template-guided “grow-in-place” approach. The resulting SiNW FETs exhibit an on-off ratio of 106 and a subthreshold slope of 130mV/decade. These transistors can allow unique design flexibility; for example, a NAND gate can be achieved in a uniformly doped nanowire with four contacts.