Realizing an N-Type Organic Thermoelectric ZT of 0.46

Abstract

The performance of n-type organic thermoelectric materials is significantly limited by a lack of a deep understanding of the structure–property relationship. In this study, we aim to establish a connection between the molecular structure and the density of states (DOS) profile related to thermoelectric performance. We synthesized three new diketopyrrolopyrrole-based polymers, each functionalized with amphipathic side chains. The only difference among these polymers is the number of sp²-N substitutions. Our findings indicate that as the number of substitutions increases, the DOS profile widens and intensifies, creating new peaks that extend toward the bandgap. This enables more efficient doping and coherent charge transport. Consequently, we achieved a high electrical conductivity of 63.8 S cm^–1, a power factor of 111.8 μW m^–1 K^–2, and a ZT of 0.46, representing a significant advancement in n-type organic thermoelectrics. This work provides valuable guidelines for designing high-performance thermoelectric materials by rationally tailoring the DOS profile.