Dichlorinated Dithienylethene‐Based Copolymers for Air‐Stable n‐Type Conductivity and Thermoelectricity
Jinfeng Han, Huidong Fan, Qingyang Zhang, Qin Hu, Thomas P. Russell, Howard E. Katz
Abstract
Abstract Two donor–acceptor (D–A) polymers are 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. A high electron conductivity of 38.3 and 16.1 S cm −1 are obtained from the chlorinated and fluorinated polymers with N‐DMBI, respectively, and 12.4 and 2.4 S cm −1 are obtained from the chlorinated and fluorinated polymers with CoCp 2 , respectively, from drop‐cast devices. The corresponding power factors are 22.7, 7.6, 39.5, and 8.0 µ W 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 µ W 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 and atomic force microscopy.