Oligothiophene-terminated poly(ethylene glycol) was synthesized and used as a non-ionic and amphiphilic surfactant for fabricating high-quality single-walled carbon nanotube (SWCNT) films by a simple spin coating method. The absence of charge repulsion between SWCNT/surfactant complexes successfully leads to formation of a dense network of SWCNTs on the substrate through a single deposition of spin coating. When the SWCNT film was treated with nitric acid and thionyl chloride after washed with dichloromethane and water, a high-performance SWCNT film with the sheet resistance of 59 ohm/sq and the transparency of 71% at 550 nm was successfully obtained. Since the SWCNT film exhibits a high value of σ(dc)/σ(ac) (∼17) and excellent dimensional stability after releasing from the substrate, the film can be used as a transparent electrode in flexible optoelectronic devices.

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A well defined diblock copolymer (P3HT-b-C(60)) based on regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was synthesized via two controlled polymerization steps and used as a compatibilizer for the P3HT/PCBM blend, which has widely been used as an active layer in bulk heterojunction polymer solar cells. The addition of a small amount of P3HT-b-C(60) results in not only the reduction of phase size of P3HT/PCBM blend but also the suppression of macrophase separation for long-time thermal annealing owing to the preferential location of the diblock copolymers at the interface between P3HT and PCBM phases. The morphology change with the annealing time is closely related to the change of the power conversion efficiency (PCE) of solar cells: the PCE of P3HT/PCBM greatly decreases with increasing annealing time while the addition of P3HT-b-C(60) significantly reduces the decrease of PCE for long-time thermal annealing.

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Two types of temperature sensor which have pyrene (Pyr) and fullerene (C60) attached to poly(Nisopropylacrylamide) (PNIPAM) are synthesized, and their thermal sensitivities are examined in terms of the fluorescence quenching efficiency of C60: One is pyrene-poly(N-isopropylacrylamide)-fullerene (Pyr-PNIPAM-C60) which has Pyr and C60 attached to each chain end of PNIPAM, and the other is pyrene-poly(Nisopropylacrylamide-co-fullerenylethyl methacrylate) (Pyr-P(NIPAM-co-C60)) which has Pyr attached to one chain end of PNIAPM and two C60s attached onto PNIPAM backbone. Both of them exhibit the same conformational change from coil to globule at a specific temperature, which results in drastic on-and-off quenching efficiency. The quenching efficiency of Pyr-P(NIPAM-co-C60) is larger than Pyr-PNIPAM-C60, since Pyr-P(NIPAN-co-C60) has more C60s located closer to Pyr than Pyr-PNIPAM-C60. These C60-based thermosensitive polymers exhibit well-defined on-and-off behavior at a small change in temperature.

A graft copolymer, poly(styrene sulfonic acid) grafted with polyaniline (PSSA-g-PANI), is synthesized and used as the hole transport layer in polymer solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester. Electrochemical stability of PSSA-g-PANI is superior to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which has widely been used as the hole transport material in polymer solar cells. The unique high transparency in 450−650 nm wavelength and high electrical conductivity of PSSA-g-PANI result in higher short circuit current and higher open circuit voltage of polymer solar cells than those of the device made of PEDOT:PSS. A series of PSSA-g-PANI with different electrical conductivities are synthesized to investigate the effect of conductivity on the performance of polymer solar cells. The device with the most conductive PSSA-g-PANI exhibits the highest power conversion efficiency (∼4%), which is 20% higher than that of the device with PEDOT:PSS.

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