B←N-Incorporated Dibenzo-azaacenes as n-Type Thermoelectric Materials.

Organic thermoelectric materials play a vital role in flexible power generating applications, such as wearable electronics and sensor networks. While there is a wealth of research on p-type organic thermoelectric materials, developments on n-type counterparts as complementary are comparatively limited. Herein, we report a new kind of n-type small-molecule thermoelectric materials based on B←N-incorporated dibenzo-azaacenes 1,2-DBNA-2 and 1,2-DBNA-5. Because of the low-lying lowest unoccupied molecular orbital (LUMO) energy levels, 1,2-DBNA-2 and 1,2-DBNA-5 could be efficiently n-doped, and the rigid and almost planar skeleton could ensure good carrier transfer. When doped with a typical n-dopant (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI), 1,2-DBNA-5 exhibits a moderate conductivity of 0.01 S cm-1 and a power factor of 0.06 μW m-1 K-2 with a Seebeck coefficient of -244.4 μV K-1 in thermoelectric devices. These results not only demonstrate that B←N-incorporated dibenzo-azaacenes are a novel class of n-type thermoelectric materials but also highlight a new strategy to develop n-type organic thermoelectric materials.