Self‐Powered Broad‐Spectrum UV Photodetectors Based on TiO ₂ /Graphene/Acid‐Doped Polyaniline Heterojunction

ABSTRACT

The development of high‐performance, self‐powered ultraviolet photodetectors (UVPDs) is crucial for the practical application of low‐power‐consumption optoelectronic devices. However, achieving both broad‐spectrum detection and high sensitivity remains a challenge. In this work, a TiO ₂ ‐based ternary heterojunction composite electrode is developed. A strong built‐in electric field is established by utilizing the large potential difference between TiO ₂ and polyaniline (PANI). By introducing graphene as the charge transport layer, it can overcome issues such as recombination mismatch at the p‐n heterojunction interface and high reverse leakage current. The results show that the dark current of the PANI/GR/TiO ₂ UVPD is as low as 7.88 × 10 ⁻¹⁰  A. Furthermore, the UVPD exhibits self‐powered response characteristics across the UVA to UVC. Additionally, its specific detectivity () at 365 nm in the UVA band reaches 1.81 × 10 ¹¹ Jones, which is 545 times that of the TiO ₂ UVPD. Density functional theory (DFT) calculations confirm that the construction of the ternary heterojunction enhances charge transport kinetics, and the space charge region formed at the interface effectively suppresses electron‐hole pair recombination. This work provides an in‐depth explanation of the carrier transport processes and mechanisms within multi‐heterojunction devices, effectively advancing the development of low‐power, self‐powered detectors capable of operating across the broad ultraviolet spectrum.