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, siloxane side-chained diketopyrrolopyrrole polymers (PDPPSi_x, where x is the molar ratio of the siloxane side chain) and their corresponding FeCl₃-doped films were designed and synthesized by the solution-processed drop-casting method to improve the thermoelectric properties. The results show that the addition of siloxane side chains enhances the crystallinity and doping efficiency of the DPPSi_x 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 those of polymer films without siloxane side chains, respectively. The synergistic effect between siloxane side chains and FeCl₃ doping significantly increases the charge carrier concentration and mobility and 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.