A Novel Photo‐Activated Dopant for n‐Type Organic Thermoelectrics

Abstract Efficient and air‐stable molecular dopants are critical for optimizing the performance of thermoelectric devices. Despite significant advancements in developing p ‐dopants for organic semiconductors, the quest for efficient and air‐stable n ‐dopants remains challenging. Here, viologen‐tetraarylborate (VT) is introduced as a promising n‐dopant for thermoelectric applications, demonstrating its remarkable photo‐activation efficiency. After just 1 min of light exposure, a maximum power factor of 8.6 µW m −1 K −2 , with a conductivity of 0.86 S cm −1 and a Seebeck coefficient of −346 µV K −1 , is achieved for the VT doped PNDI2TEG‐2Tz film. Furthermore, VT exhibits excellent air stability, simplifying the device preparation process by allowing films to be prepared in ambient conditions. Additionally, the unique doping mechanism imparts good air stability to the stock solution of VT and the conjugated polymer, ensuring that the storage time of the stock solution does not affect thermoelectric performance. This innovative approach not only highlights the potential of VT as an efficient n‐dopant but also paves the way for developing novel air‐stable dopants and advancing doping methodologies in thermoelectric material research.