The semiconductor–dielectric interface significantly affects the performance and the reliability of field-effect transistors. Controlling this interface is an important issue to improve device performance in the organic electronics community. Here we report an approach that utilizes an organic heterointerface to improve the crystallinity and control the morphology of an organic thin film. Pentacene is used as an active layer above, and m-bis(triphenylsilyl)benzene (TSB3) is used as the bottom layer. Sequential evaporations of these materials result in high-quality organic thin films with indistinct grain boundaries and nanometre-sized pores. The pentacene film exhibits high mobility, and the pore-rich structure improves the sensitivity of organic-transistor-based chemical sensors.