Solvent boiling point affects the crystalline properties and performances of anthradithiophene-based devices

We investigated the effects of the solvent boiling point on organic field-effect transistor (OFET) device performances in devices prepared using two newly synthesized anthradithiophene derivatives: 9,10-di(4′-pentylphenylethynyl)-anthra[2,3-b:6,7-b′]dithiophene (DPPEADT) and 9,10-bi([9′,9′-dimethyl-fluoren-2-ylethynyl])-anthra[2,3-b:6,7-b′]dithiophene (DFEADT). DPPEADT exhibited a distinct crystalline morphology whereas DFEADT was amorphous. We characterized the relationship between the molecular structures, film morphologies, and OFET device performances in devices prepared using solvents having one of three different boiling points (chlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene). 1,2,4-Trichlorobenzene, which provided the highest boiling point among the solvents tested and acted as a good solvent for DPPEADT, significantly improved the field-effect mobilities of DPPEADT devices up to 0.16 cm²/V by enhancing the crystallinity of the film. OFETs based on amorphous DFEADT films prepared using the three solvents did not provide enhanced electrical performances. The differences between the transistor performances were attributed to the degree of π-overlap, the molecular structures, and the morphological properties of the films.