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  1. A novel n-type copolymer dopant polystyrene-polyvinyl hexylpyridinium fluoride (PSpF) with fluoride anion is designed and synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. To our knowledge, it is the first polymeric fluoride dopant. Electrical conductivity of 4.2 S cm-1 and high power factor of 67 μW m-1 K-2 are achieved for PSpF doped polymer films, with a corresponding decrease in thermal conductivity as the PSpF concentration is increased, giving the highest ZT of 0.1. An especially high electrical conductivity of 58 S cm-1 at 88 ℃ and outstanding thermal stability were recorded. Further, organic transistors of PSpF-doped thin films exhibitmore »high electron mobility and Hall mobility of 0.86 and 1.70 cm2 V-1 s-1, respectively. The results suggest that polystyrene-polyvinyl pyridinium salt copolymers with fluoride anion are promising for high performance n-type all-polymer thermoelectrics. This work provides a new way to realize organic thermoelectrics with high conductivity relative to Seebeck coefficient, high power factor, thermal stability and broad processing window.« less
    Free, publicly-accessible full text available April 20, 2023
  2. A carboxylated thiophene polymer-based chemiresistive device in a field-effect transistor (FET) configuration with unusual and enhanced responses to the widespread pollutants nitrogen dioxide (NO 2 ) and ammonia (NH 3 ) is described. The device based on a polymeric thiophene carboxylic acid showed a dramatic and superlinear increase in drain current ( I D ) of over 15 000% to a ramped exposure to 10 ppm NO 2 over several minutes, while its ethyl ester counterpart had significantly lower response. Devices incorporating either an ester or carboxylic acid displayed comparable and previously unreported increases in I D from 10 ppm rampedmore »NH 3 exposure of 200–300%. Conventional poly(alkylthiophenes) showed the expected current decreases from similar NH 3 exposures. Using threshold voltage shifts in silicon transistors coupled to our recently reported remote gate (RG) platform with thiophene polymer coatings, we determined that two differing response mechanisms are associated with the two gas exposures. By calculating the charge density induced in the polymers by NO 2 exposure using the silicon transistor voltage shifts, we conclude that proton conduction contributes significantly to the high sensitivity of the carboxylic acid to NO 2 , in addition to doping that was observed for all four polymers. Furthermore, hydrogen bonding moieties of the carboxylic acid and ester may be able to physisorb NH 3 and thus alter the charge distribution, rearrange polymer chains, and/or create a proton transfer network leading to the I D increase that is the opposite of the response obtained from non-carboxylated thiophene polymers.« less
  3. Free, publicly-accessible full text available October 25, 2022
  4. Free, publicly-accessible full text available October 25, 2022