Recent advances in n-type organic thermoelectric materials, dopants, and doping strategies

Recently, organic thermoelectric (TE) materials have been intensively studied because of their great potential for application in flexible/wearable TE generators for power generation at low temperatures. However, reports on the development of efficient n-type TE materials and their TE properties are much less in number than those on p-type TE materials. Significant efforts have been recently directed toward the development of n-type organic TE materials, n-dopants, and doping methods. Outstanding advances have been achieved in this field, and various n-type structures with TE performance comparable to that of p-type structures have been developed. The molecular library of novel n-type building blocks and the resulting n-type small molecular and polymeric TE materials, as well as n-dopants, has been significantly extended. In this regard, we believe that it would be of great significance to review the recent advances in the field of n-type organic TE materials and highlight important scientific breakthroughs. In this review, the recent developments in the fields of n-type organic TE materials and n-type dopants, as well as innovative doping techniques are discussed. Finally, the current challenges and future prospects are discussed to provide guidelines for the development of high-performance n-type TE materials.