In this work, we investigated how the electrical and photoelectrical properties of InSe based devices depend on the interfaces made with standard materials such as SiO₂, BN, and PMMA. The use of a BN layer is found to not only change the carrier type but also weaken the out-of-plane vibration of InSe. Field-effect transistor devices show a p-type behavior for InSe on SiO₂, while for InSe on BN, the majority carriers are electrons. Moreover, due to the weakened electron–phonon interaction the electron mobility of InSe on BN is more than two magnitudes greater than its hole mobility on SiO₂. A p–n junction diode is also demonstrated with InSe/SiO₂ and InSe/BN with a rectification ratio as high as 10² and a photoresponsivity of 52 A/W, which can be enhanced to 10³ and 1.6 × 10⁴ A/W with a PMMA coverlayer. Our results may be useful for the design of high-performance van der Waals heterojunction photodetectors.