Molecular Insights into n-Type Organic Thermoelectrics

Organic thermoelectrics (OTEs) have been recently intensively investigated as they hold promise for flexible, large-area, and low-cost energy generation or heating–cooling devices for appealing applications, for example, wearable energy harvesting. In the past 7 years, n-type OTEs have witnessed a sharp increase in their performance thanks to significant progress in developing and understanding the fundamental physical properties of n-type OTE materials as well as the working principle and physical processes of the TE devices. In this mini review, we briefly review the advances and strategies of designing the n-type OTEs. More importantly, we discuss the effects of molecular structure of the n-type organic semiconductors on the fundamental physical processes such as charge transfer, separation, and transport, highlighting the key differences of the pristine and doped OTEs at the microscopic level. Finally, the remaining challenges and future outlooks of research are discussed. We aim to establish profound understanding of the structure–property–performance relationship to provide useful guidelines for the molecular design of high-performance n-type OTEs for promising future OTE technology.