Theoretical Studies of Bipolar Transport in CnBTBT–FmTCNQ Donor–Acceptor Cocrystals

The development of crystals with bipolar transport characteristics is essential for high-performance organic field effect transistor (OFET) devices. In this work, we theoretically investigated the bipolar transport behaviors in CnBTBT–FmTCNQ cocrystals. It is found that bipolar transport can be realized in C8BTBT–TCNQ and C12BTBT–TCNQ cocrystals with room-temperature electron/hole mobility up to 1.8/0.75 and 2.5/1.8 cm2 V–1 s–1, respectively. The comparable electron- and hole-transfer integrals between the nearest-neighbor molecule pairs as well as the small hole reorganization energy of the TCNQ molecule are responsible for the balanced electron and hole mobilities. Moreover, because of the π–π stacking between neighboring molecules, all cocrystals show strong anisotropic transport characteristic for both electron and hole transport with the mobility along the π–π stacking direction much larger than those along the other two directions. This work provides the possibility of high-performance OFET engineer...