Siloxane engineered polydiketopyrrolopyrrole derivatives with improved crystallinity and doping efficiency for thermoelectric power generation

Siloxane side engineered conjugated polymers exhibit good film forming capabilities and have been reported for a variety of advanced energy applications. However, their potential for regulating polymer crystallinity to achieve high thermoelectric (TE) properties remains unexplored. In this study, the siloxane side-chained diketopyrrolopyrrole polymers (PDPPSix, where x is the molar ratio of siloxane side chain) and its corresponding FeCl3-doped films were designed and synthesized by solution-processed drop-casting method to improve the thermoelectric properties. The results show that the addition of siloxane side chains enhance the crystallinity and doping efficiency of the DPPSix polymers, and thus improves the conductivity and TE performance. It is worth noting that the 5-min FeCl3-doped PDPPSi50 film exhibits excellent thermoelectric properties, with an electronic conductivity of 66.29 S cm-1 and a maximum power factor (PF) of 38.6 μW m-1 K-2, which are about 7-fold and 3-fold higher than that of polymer film without siloxane side chains, respectively. The synergistic effect between siloxane side chains and FeCl3 doping significantly increases the charge carrier concentration and mobility, enhances the conductivity and thermoelectric efficiency of DPP-based TE polymers. This study highlights the potential of solution-processed, inorganic-doped, and side chain engineered conjugated polymer films for enhancing thermoelectric power generation.