title: Molecular Design of Polymer Heterojunctions for Efficient Solar-Hydrogen Conversion.
abstract: Semiconducting photocatalytic solar-hydrogen conversion (SHC) from water is a great challenge for renewable fuel production. Organic semiconductors hold great promise for SHC in an economical and environmentally benign manner. However, organic semiconductors available for SHC are scarce and less efficient than most inorganic ones, largely due to their intrinsic Frenkel excitons with high binding energy. In this study the authors report polymer heterojunction (PHJ) photocatalysts consisting of polyfluorene family polymers and graphitic carbon nitride (g-C3N4) for efficient SHC. A molecular design strategy is executed to further promote the exciton dissociation or light harvesting ability of these PHJs via alternative approaches. It is revealed that copolymerizing electron-donating carbazole unit into the poly(9,9-dioctylfluorene) backbone promotes exciton dissociation within the poly(N-decanyl-2,7-carbazole-alt-9,9-dioctylfluorene) (PCzF)/g-C3N4PHJ, achieving an enhanced apparent quantum yield (AQY) of 27% at 440 nm over PCzF/g-C3N4. Alternatively, copolymerizing electron-accepting benzothiadiazole unit extended the visible light response of the obtained poly(9,9-dioctylfluorene-alt-benzothiadiazole)/g-C3N4PHJ, leading to an AQY of 13% at 500 nm. The present study highlights that constructing PHJs and adapting a rational molecular design of PHJs are effective strategies to exploit more of the potential of organic semiconductors for efficient solar energy conversion.
authors.affiliation: International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Physics, Tamkang University, 151 Yingzhuan Rd., New Taipei City, 25137, Taiwan.
authors.forename: Chung-Li
authors.initials: CL
authors.lastname: Dong
authors.affiliation: International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
authors.forename: Daming
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Department of Physics, Tamkang University, 151 Yingzhuan Rd., New Taipei City, 25137, Taiwan.|National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu, 30076, Taiwan.
authors.forename: Yu-Cheng
authors.initials: YC
authors.lastname: Huang
authors.affiliation: International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
authors.forename: Xixi
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Leith
authors.initials: L
authors.lastname: Samad
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Lianna
authors.initials: L
authors.lastname: Dang
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors.forename: Melinda
authors.initials: M
authors.lastname: Shearer
authors.affiliation: International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.|Xi'an Jiaotong University Suzhou Academy, Suzhou, Jiangsu, 215123, China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Shen
authors.affiliation: International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
authors.forename: Liejin
authors.initials: L
authors.lastname: Guo
keywords: graphitic carbon nitride; molecular design; polyfluorene family polymers; polymer heterojunctions; solar-hydrogen conversion