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This letter reports that the performance of organic solar cells made from blended films of regioregular poly 3-hexylthiophene and methanofullerene can be boosted by introducing single-walled carbon nanotubes (SWCNTs) into the active layer at low concentration. However, the performance degrades at higher SWCNTs concentration. The intensity dependent photocurrent measurement shows that the decreased performance at higher concentration of SWCNTs is attributed to bimolecular recombination in the presence of metallic SWCNTs. Meanwhile, it has been found that the increased performance at low concentration of SWCNTs is due to the increased carrier mobility as semiconducting SWCNTs provide lower resistance pathways.

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AlInAs/GaInAs npn heterojunction bipolar transistors (HBTs) have been grown over a substrate temperature range of 280–450 °C with Be base doping levels ranging from 2.0×1019 to 1.6×1020 cm−3. We have determined that for a desired base doping level there exists an optimum growth temperature at which the Be is confined in the base and at the same time the dc current gain of the HBT is maximized.

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