The authors report that polypyrrole (PPy) films with large area and high crystalline quality have been achieved using an interfacial chemical oxidation method. By dissolving different reactants in two immiscible solvents, the PPy is synthetized at the interface region of the two solutions. The PPy films have sharp XRD diffraction peaks, indicating that the molecular chains in the film are arranged in a high degree of order and that they reflect high crystalline quality. High crystal quality is also conducive to improving electrical conductivity. The conductivity of the as prepared PPy film is about 0.3 S/cm, and the carrier mobility is about 5 cm2/(Vs). In addition, the biggest advantage of this method is that the prepared PPy film has a large area and is easy to transfer to other substrates. This will confidently broaden the application of PPy in the future.

Deep ultraviolet monitoring is realized via a high crystal quality SnO2 microwire (MW)‐based photodetector (PD). This is then combined with 2D nitrogen‐doped graphene (NGr), conducting polymer polypyrrole (PPy), and an in situ polymerization‐fabricated composite film PPy‐NGr to construct an organic–inorganic p–n heterojunction PD. The long response time brought on by the oxygen adsorption of SnO2 MW is greatly decreased via coating with the aforementioned materials. A defect response is created by the surface dangling bonds of SnO2 MW, which can be effectively suppressed by the PPy. Absorption in the deep ultraviolet region (<240 nm) by PPy results in a blue shift of the response peak of the PPy/SnO2 heterojunction PD compared to that of a single SnO2 PD. The introduction of NGr improves the detection performance by providing a smoother energy band migration to reduce photogenerated carrier recombination and stacking at the potential barrier. The ultrahigh responsivity of PPy‐NGr/SnO2 PD is 4594.25 A W−1 and the detectivity is 6.47 × 1011 Jones, 40 and nine times greater, respectively, than those of a PPy/SnO2 PD under a 5 V reverse bias and 240‐nm light irradiation (18.75 µW cm−2). The novel strategy provides a reference for the future design of high‐performance heterojunction PDs.