Understanding the Solution‐State Doping of Donor–Acceptor Polymers Through Tailored Side Chain Engineering for Thermoelectrics

Abstract

Among the molecular doping methods widely utilized to control charge carriers in organic thermoelectric (TE) devices, solution mixing is attractive for the preparation of uniform and thick TE films to obtain high output powers. However, the effects of doping behavior in solution‐state polymers on their film properties are still not well understood, particularly for donor–acceptor (D‐A) polymers, key materials for high‐performance (opto)electronic devices. Here, by preparing three D‐A polymers with engineered side chains, the aggregation effects of D‐A polymers on the doping behavior in the solution and film states are demonstrated. In a less aggregated polymer, mixing the solution with a p‐dopant leads to the Lewis complex formation, which reduces doping efficiency and power factor. However, solution mixing of aggregated polymers induces the formation of ion pairs with the dopant, resulting in power factors that are two orders of magnitude higher at 23.7 µW m−1 K−2. Doping in the film state where aggregation is induced facilitates ion‐pair formation, resulting in smaller deviation in TE properties (power factors = 9.0–16.4 µW m−1 K−2) despite differences in their ordering structures. These results provide an in‐depth understanding of efficient solution‐state doping of D‐A polymers for TEs.

A multifunctional paper-based supercapacitor with excellent temperature adaptability, plasticity, tensile strength, self-healing, and high thermoelectric effects

“…In recent years, the Seebeck effect, which uses ions as carriers, has opened up a new way to develop high-performance thermoelectric devices. 43–46 However, the currently reported ionic thermoelectric materials are still limited by various factors, and there are some bottlenecks that are difficult to overcome: most of the ionic thermoelectric materials are gel-containing water-soluble solutions, and the liquids are prone to evaporation or leakage, resulting in poor stability, and the ionic thermoelectric materials are mainly p-type. The choice of n-type materials with high mechanical stability and flexibility is very limited.…”

“…In recent years, the Seebeck effect, which uses ions as carriers, has opened up a new way to develop high-performance thermoelectric devices. [43][44][45][46] However, the currently reported ionic thermoelectric materials are still limited by various factors, and there are some Fig. 7 (a) Self-healing experiment, (b) repeatable self-healing experiment, (c) experiment of self-healing effect on a small bulb, with on and off based on the APC-PVA@ZnCl 2 material.…”

Design of Donor–Acceptor Polymer Semiconductors for Optimizing Combinations with Dopants to Maximize Thermoelectric Performance

“…PBDTC2FBT was doped by using two different dopant candidates and processes. Because FeCl 3 and BCF are regarded as different optimized doping processes owing to their solubility differences, − (1) as-prepared PBDTC2FBT films were sequentially doped with an overcoating FeCl 3 solution (sequential doping), and (2) BCF was mixed with PBDTC2FBT in the solution state (solution mixing) to obtain each doped PBDTC2FBT film. For sequential doping with FeCl 3 , optimized conditions were determined after thermal annealing to induce molecular self-assembly.…”

Remarkable conductivity enhancement in P-doped polythiophenes via rational engineering of polymer-dopant interactions

“…Herein, we show that high mobility can be achieved in doping random copolymers comprising weakly ordered connected aggregates, representing a new pathway to realize efficient charge transport, especially in the low crystalline polymers. Particularly, since many of the emerging classes of conjugated polymers are low-crystalline donor-acceptor polymers that are near-amorphous in their pristine state [73,74], it is thus important to develop an alternative route to achieve a favorable charge transport landscape.…”