Organic thin film transistors with improved mobility are disclosed. The semiconducting layer comprises a semiconductor material of Formula (I): wherein R1 and R2 are independently selected from alkyl, substituted alkyl, aryl, and substituted aryl; and R3 and R4 are independently selected from hydrogen, alkyl, substituted alkyl, aryl, and substituted aryl. A silanized interfacial layer is also present which has alkyl sidechains extending from its surface towards the semiconducting layer.