Radical-Mediated Dispersion Breaks Aggregation Limits in Carbon Thermoelectrics

Carbon-based materials, particularly single-walled carbon nanotubes (SWCNTs), are promising candidates for flexible thermoelectric applications due to their excellent electrical conductivity and mechanical robustness. However, severe self-aggregation of SWCNTs leads to suboptimal and degraded thermoelectric performance. Conventional dispersion strategies have proved largely ineffective in overcoming this limitation. Here, we present a pioneered radical-mediated dispersion (RMD) strategy, enabled by a rationally designed small molecule, OTN, which incorporates a donor-acceptor conjugated backbone and pendant free-radical terminals. The RMD strategy mechanism functions through dual interactions: The donor-acceptor backbone enhances π-interactions with SWCNTs, while the pendant radicals facilitate radical-radical interactions to further suppress nanotube aggregation. This synergistic molecular design enables OTN-SWCNT hybrid films to achieve a high power factor of 30.1 µW cm^-1 K^-2, far exceeding previous reports, while maintaining excellent free-standing mechanical flexibility. Furthermore, a nine-leg thermoelectric device assembled from these films delivers a normalized power density of 0.653 µW cm^-2 K^-2, representing one of the best performances for CNT-based thermoelectrics to date. This pioneering molecular design, together with the derived innovative RMD strategy overcomes the long-standing aggregation of SWCNTs and is anticipated to open new avenues for advancing carbon-based thermoelectric materials toward practical, flexible energy-harvesting applications.