Co-Crystallization of Grafted BTBT-Containing Siloxane Copolymer with C8-BTBT for the Stabilization of OFET Electrical Performance

Despite significant advances in the development of organic semiconductors (OSCs) for organic field-effect transistors (OFETs), there is still a great demand for materials with high charge carrier mobility and long-term stability to enable the wide application of OFETs. An effective method to combine the high charge carrier mobility of small-molecule OSCs with the stability of polymers is to use their blends. In this work, a siloxane copolymer P50 containing 50% of methylsiloxane units grafted with undecyl-[1]benzothieno[3,2- b ][1]benzothiophene-octyl (C11-BTBT-C8) side groups was mixed with a small-molecule OSC 2,7-dioctyl[1]benzothieno[3,2- b ][1]benzothiophene ( C8-BTBT) to facilitate their cocrystallization. The formation of cocrystalline lamellas of P50/C8-BTBT was confirmed by differential scanning calorimetry and X-ray scattering data, which allowed us to suggest a model of BTBT units packing in P50/C8-BTBT cocrystals. The OFETs using these blends demonstrated significantly improved long-term stability with the charge carrier mobility up to 0.45 cm 2 V –1 s –1, which is similar to the mobility of pure C8-BTBT devices obtained under the same conditions.