Dramatic Responsivity Enhancement Through Concentrated H₂ SO₄ Treatment on PEDOT:PSS/TiO₂ Heterojunction Fibrous Photodetectors

In order to satisfy the growing requirements of wearable electronic devices, 1D fiber-shaped devices with outstanding sensitivity, flexibility, and stability are urgently needed. In this study, a novel inorganic-organic heterojunction fibrous photodetector (FPD) based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and highly ordered TiO₂ nanotube array is fabricated, which endows a high responsivity, large external quantum efficiency, and fast response speed at 3 V bias. To further ameliorate its performance in the self-powered mode, a facile acid treatment is adopted and the assembled H-PEDOT:PSS/TiO₂ FPD demonstrates outstanding self-powered properties with ≈3000% responsivity enhancement (161 mA W^-1 at 0 V under 365 nm irradiation, photocurrent enhancement of ≈50 times) compared with the untreated device. It is found that the concentrated H₂ SO₄ post-treatment helps decrease the tube wall thickness of TiO₂ and partially removes the insulated PSS component in PEDOT:PSS, leading to enhanced conductivity and facilitated charge transportation, and thereby superb responsivity/photocurrent enhancement of self-powered H-PEDOT:PSS/TiO₂ FPD. This low-cost and high-performance self-powered FPD shows high potential for applications in wearable electronic devices.