Dichlorinated Dithienylethene-Based Copolymers for Air-Stable n-Type Conductivity and Thermoelectricity

• Published in: Advanced functional materials 2020-10, Vol.31 (5)
• Main Authors: Han, Jinfeng, Fan, Huidong, Zhang, Qingyang, Hu, Qin, Russell, Thomas P., Katz, Howard E.
• Format: Article
• Language: English
• Subjects: 30 DIRECT ENERGY CONVERSION; air stability; dichlorinated dithienylethene; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; n-type; organic thermoelectricity
• ISSN: 1616-301X; 1616-3028

Here, two donor-acceptor polymers were obtained by coupling difluoro- and dichloro-substituted forms of the electron-deficient unit BDOPV and the relatively weak donor moiety dichlorodithienylethene (ClTVT). The conductivity and power factors of doped devices are different for the chlorinated and fluorinated BDOPV polymers. High electron conductivity of 38.3 and 16.1 S cm-1 were obtained from the chlorinated and fluorinated polymers with N-DMBI, respectively, and 12.4 and 2.4 S cm-1 were obtained from the chlorinated and fluorinated polymers with CoCp2, respectively, from drop-cast devices. The corresponding power factors are 22.7, 7.6, 39.5 and 8.0 μW m-1 K-2, respectively. Doping of PClClTVT with N-DMBI results in excellent air-stability; the electron conductivity of devices with 50 mol% N-DMBI as dopant remained up to 4.9 S m-1 after 222 days in the air, the longest for an n-doped polymer stored in air, with a thermoelectric power factor of 9.3 μW m-1 K-2. However, the conductivity of PFClTVT-based devices can hardly be measured after 103 days. These observations are consistent with morphologies determined by grazing incidence wide angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM). The results demonstrate that chemical structures leading to dense and ordered packing can enhance electron conductivity and air stability of n-type donor-acceptor polymers.