Cinnamate-Functionalized Natural Carbohydrates as Photopatternable Gate Dielectrics for Organic Transistors

Photolithographic-defined films play an important role in modern optoelectronics and are crucial for the development of advanced organic thin-film transistors (OTFTs). Here, we explore a facile photoresist-free photopatterning technique with natural carbohydrates and its use as an OTFT gate dielectric. The effects of the cross-linkable chemical structure on the cross-linking chemistry and dielectric strength of the corresponding films are investigated in cinnamate-functionalized carbohydrates from monomeric (glucose) to dimeric (sucrose) to polymeric (cellulose) backbones. UV illumination of the cinnamate esters of these carbohydrates leads to [2 + 2] cycloaddition and thus the formation of robust cross-linked dielectric films in the irradiated areas. Using propylene glycol monomethyl ether acetate as the solvent/developer, patterned dielectric films with micrometer-sized features can be readily fabricated. P- and N-type OTFTs are successfully demonstrated using unpatterned/patterned cross-linked films as the gate dielectric and pentacene and N,N′-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN₂) as the p- and n-channel semiconducting layers, respectively. These results demonstrate that natural-derived polymer gate dielectrics, which are soluble and patternable using biomass-derived solvents, are promising for the realization of a more sustainable OTFT technology.