Dithienobenzothiadiazole‐Based Conjugated Polymer: Processing Solvent‐Relied Interchain Aggregation and Device Performances in Field‐Effect Transistors and Polymer Solar Cells

DT f BT‐Th 3 , a new conjugated polymer based on dithienobenzothiadiazole and terthiophene, possesses a bandgap of ≈1.86 eV and a HOMO level of −5.27 eV. Due to strong interchain aggregation, DT f BT‐Th 3 can not be well dissolved in chloro­benzene (CB) and o ‐dichlorobenzene (DCB) at room temperature (RT), but the polymer can be processed from hot CB and DCB solutions of ≈100 °C. In CB, with a lower solvation ability, a certain polymer chain aggregation can be preserved, even in hot solution. DT f BT‐Th 3 displays a field‐effect hole mobility of 0.55 cm 2 V −1 s −1 when fabricated from hot CB solution, which is higher than that of the device processed from hot DCB (0.16 cm 2 V −1 s −1 ). In DT f BT‐Th 3 ‐based polymer solar cells, a good power conversion efficiency from 5.37% to 6.67% can be achieved with 150−300 nm thick active layers casted from hot CB solution, while the highest efficiency for hot DCB‐processed solar cells is only 5.07%. The results demonstrate that using a solvent with a lower solvation ability, as a “wet control” process, is beneficial to preserve strong interchain aggregation of a conjugated polymer during solution processing, showing great potential to improve its performances in optoelectronic devices. image