Enhanced Thermoelectric Properties of Two-dimensional Planar Copper Polyphthalocyanine by Dispersing Single-walled Carbon Nanotubes

Two-dimensional planar metal polyphthalocyanine is considered a kind of promising organic thermoelectric material due to its unique molecular structure and high carrier mobility, but its low carrier concentration and low electrical conductivity impede improvement of thermoelectric performance. In this work, copper polyphthalocyanine/single-walled carbon nanotubes (CuPPc/SWCNTs) composites were prepared by in-situ polymerization and mechanical ball-milling, respectively. As compared with ball-milled sample (BM-CuPPc/SWCNTs), in-situ polymerized sample (IS-CuPPc/SWCNTs) presents strong π-π conjugation between CuPPc and SWCNTs, which can effectively reduce the interfacial resistance between CuPPc and SWCNTs. Therefore, IS-CuPPc/SWCNTs shows higher electrical conductivity than BM-CuPPc/SWCNTs at high SWCNTs concentration. With 80% (in mass) SWCNTs, the electrical conductivity of IS-CuPPc/SWCNTs reaches 1.31×104 S·m -1, 30% higher than that of BM-CuPPc/SWCNTs, and six orders of magnitude higher than that of pure CuPPc. Meanwhile, the maximum thermoelectric power factor of IS-CuPPc/SWCNTs reaches 18.24 μW·m-1·K-2, which is higher than that of BM-CuPPc/SWCNTs and surpasses that of pure CuPPc by six orders of magnitude. This study provides an effective way to enhance the thermoelectric properties of metallic polyphthalocyanine.