Deep Ultraviolet Photodetector with Ultrahigh Responsivity based on a Nitrogen-Doped Graphene-Modified Polypyrrole/SnO2 Organic/Inorganic p–n Heterojunction

Deep ultraviolet monitoring is realized via a high crystal quality SnO 2 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 SnO 2 MW is greatly decreased via coating with the aforementioned materials. A defect response is created by the surface dangling bonds of SnO 2 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/SnO 2 heterojunction PD compared to that of a single SnO 2 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/SnO 2 PD is 4594.25 A W −1 and the detectivity is 6.47 × 10 11 Jones, 40 and nine times greater, respectively, than those of a PPy/SnO 2 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.