title: A cyclopenta[1,2-b:5,4-b']dithiophene-porphyrin conjugate for mesoscopic solar cells: a D-π-D-A approach.
abstract: This work introduces cyclopenta[1,2-b:5,4-b']dithiophene (CPDT) as a spacer between the porphyrin chromophore and cyanoacetic acid to obtain a porphyrin dye (coded as LW9). The resultant novel porphyrin dye exhibits extended absorption spectra and a split B band at 520 nm. Therefore, a full spectrum light harvesting characterization of sensitized TiO2 mesoporous film can be achieved. To conduct a thorough investigation of the influence of the spacer unit, new sensitizers conjugated with biphenyl (LW7) and bithiophene (LW8) have been synthesized. As the electron-donating ability of the spacer varies from biphenyl to bithiophene and cyclopenta[1,2-b:5,4-b']dithiophene, stepwise red-shifted electronic absorption spectra and the consistently decreasing energy gap of the dye are presented. These novel porphyrins have been evaluated in dye-sensitized solar cells, achieving a power efficiency of 6.5% employing a [Co(bpy)3](2+/3+) redox couple for the LW9 device under reporting conditions. Detailed investigation, including time-resolved photoluminescence, transient photovoltage decay, and scanning electrochemical spectroscopy measurements, provides important information on the factors affecting the principal photovoltaic parameters. The present report highlights the potential of D-π-D-A porphyrin for the development of efficient sensitizers with broad light absorption properties.
authors.affiliation: Michael Grätzel Center for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, P. R. China. mingkui.wang@mail.hust.edu.cn ciac_sheny@mail.hust.edu.cn.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Lu
authors.forename: Bingyan
authors.initials: B
authors.lastname: Zhang
authors.forename: Shuangshuang
authors.initials: S
authors.lastname: Liu
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.forename: Huailiang
authors.initials: H
authors.lastname: Yuan
authors.forename: Yan
authors.initials: Y
authors.lastname: Shen
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.forename: Yibing
authors.initials: Y
authors.lastname: Cheng
authors.forename: Mingkui
authors.initials: M
authors.lastname: Wang