Phase separation and electrical performance of bithienopyrroledione polymer semiconductors embedded in insulating polymers

Abstract

Bithienopyrroledione (1,1′-bithieno[3,4-c]pyrrole-4,4′,6,6′-tetraone (bi-TPD)) based copolymer P1 was synthesized and characterized. Its phase separation characteristics in a P1/PMMA blend were investigated. It was found that P1 formed microsized fibers in the P1/PMMA blend and dispersed into the whole blend system. Thin film field-effect transistors using P1 films and P1/PMMA blend films as active layers were fabricated. Both devices showed p-type charge carrier transport properties under ambient conditions and ambipolar charge carrier transport behavior in a N₂ atmosphere. Under ambient conditions, the P1 film transistors displayed a hole mobility of 0.48 cm² V⁻¹ s⁻¹, and the blend film devices exhibited comparable performance with a hole mobility of 0.32 cm² V⁻¹ s⁻¹. In a N₂ atmosphere, the performance of the blend film transistors was largely improved compared with that of the P1 film ones. The hole/electron mobilities were 0.10/0.05 cm² V⁻¹ s⁻¹ for the blend film transistors and 0.02/0.002 cm² V⁻¹ s⁻¹ for the P1 film devices. All these results demonstrate the potential applications of bi-TPD based polymer semiconductors in high performance blend film transistors.