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Doped small molecules with high electrical conductivity are desired because they typically show a larger Seebeck coefficient and lower thermal conductivity than their polymer counterparts. However, compared with conjugated polymers, only a few small molecules can show high electrical conductivities. In this study, three n‐type small‐molecule organic semiconductors with different end functional groups are synthesized to explore the reasons for the low electrical conductivity issue in n‐doped small‐molecule semiconductors. Charge carrier mobility and doping level are usually considered as two major parameters for achieving high electrical conductivity. TDPP‐ThIC with high electron mobility of 0.77 cm2 V−1 s−1 and high electron affinity, which can be easily n‐doped; however, it only displays an electrical conductivity ≈10−3 S cm−1. To explore the reasons, the single crystal structure of TDPP‐ThIC and the grazing incidence wide‐angle X‐ray scattering of its n‐doped films are carefully analyzed. TDPP‐ThIC with a 1D column packing is disclosed and easily distorted by the enthetic n‐dopants, which damages the charge transport pathways, and thereby results in low electrical conductivity. The results suggests that only high intrinsic charge carrier mobility and high doping level cannot guarantee high electrical conductivity, and keeping good charge transport pathways after doping is also critical. [ABSTRACT FROM AUTHOR]

Compared with inorganic thermoelectric materials, organic thermoelectric (OTE) materials have attracted increasing attention due to their advantages of low toxicity, high mechanical flexibility, and large‐scale solution processability. In the past few years, OTE materials have made remarkable progress in terms of their design, synthesis, and device performance. However, some challenges remain, including the low doping efficiency in n‐type materials, poor doping stability with molecular dopants, and the largely reduced Seebeck coefficient after heavily doping, etc. All these factors hinder the further development of OTEs for commercial applications. In this Minireview, we highlight several key challenges during the development of OTEs and summarize recent understandings and efforts to address these challenges. [ABSTRACT FROM AUTHOR]

Front Cover: Recent Progress on Addressing the Key Challenges in Organic Thermoelectrics (Chem. Organic thermoelectric materials, conjugated polymers, doping, electrical conductivity, Seebeck coefficient According to the parameters that determine the values of the dimensionless figure of merit, I ZT i , discussions are divided into electrical conductivity and Seebeck coefficient related issues. [Extracted from the article]