Organic Thermoelectric Materials from n-Type Polymer Semiconductors.

Organic thermoelectric (OTE) materials have aroused increasing attention due to their potential application in wearable/flexible TE generator for energy harvesting. To meet the practical application of thermoelectric device, high-performance p- and n-type OTE materials are both necessary. In the past few years, n-type polymer semiconductors have witnessed the rapid development in OTE field, however, their thermoelectric performance is still lagging behind p-type counterparts. Therefore, more efforts should be made to enhance n-type polymer TE performance, including development of novel molecule structure, synthesis of new dopants and optimization of device engineering. In this review, we highlight the effects of molecular structure and side chain length and polarity of n-type polymer semiconductors on the TE performance such as electron transport, electrical conductivity, and power factor. Finally, further perspective and challenge are also discussed to provide useful guideline for the design of high-performance n-type OTE materials.