Solvent vapor annealing for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) thin films toward transistor fabrication

Abstract

Solvent vapor annealing (SVA) was examined for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14) thin films as the activate layer of top-contact, bottom-gate transistors. SVA with chlorobenzene vapor was performed on different types of PBTTT-C14 films; pristine films on SiO2, thermally-annealed films on SiO2, and thermally-annealed films on alkylsilane-modified SiO2. Solvent vapors penetrated into the PBTTT-C14 films and caused some similar effects as conventional post-thermal annealing, such as reduced molecular lamellae spacing and increased field-effect mobility. Additionally, the hole mobility of the thermally-annealed film on alkylsilane-modified SiO2 was increased by SVA with relatively shorter duration, even without any obvious shifts in lattice spacing and optical absorption bands of the films. This means that SVA only for the film surface and the upper part of the organic active layer may be effective for improving electrode contact interfaces in top-contact transistors. The roles of SVA for tailoring structures and field-effect carrier transport in PBTTT-C14 films are considered.