Performance optimization of self-powered deep ultraviolet photodetector based on PEDOT:PSS/SnO2 organic/inorganic p–n heterojunction by embedding a nitrogen-doped graphene

Abstract

A self-powered organic–inorganic p–n heterojunction deep ultraviolet (DUV) photodetector (PD) was fabricated based on the polymer poly(3,4-ethylene-dioxythiophene):polystyrene sulfonate (PEDOT:PSS), with an in situ transferred composite film PEDOT:PSS-nitrogen-doped graphene (NGr)-coated SnO2 microwire. At 0 V bias, the responsivity spectra of these two heterojunction PDs both had a broadband response in the range of 200–400 nm. The introduction of NGr helped to reduce the surface state of SnO2 and improve the shortwave response, resulting in a blue shift of peak position from 280 to 250 nm. Compared with PEDOT:PSS/SnO2 PD, the light–dark current ratio of the PEDOT:PSS-NGr/SnO2 PD was improved three orders of magnitude from 24.76 to 2.51 × 104; the detectivity was increased by 40 times from 1.45 × 1011 to 5.85 × 1012 Jones; and the response speed was accelerated to less than 1 s (with rise and decay times of 0.35 and 0.14 s, respectively). The performance improvement was attributed to the intermediate layer NGr forming a heterojunction with SnO2, which broadened the depletion layer of PEDOT:PSS/SnO2 and increased the strength of the built-in electric field, thereby reducing carrier recombination and boosting the response speed. These findings indicate that introducing NGr is an effective way to modify detector performance.