The applications of thin-film transistors (TFTs) based on oxide semiconductors are limited due to instability under negative bias illumination stress (NBIS). Here, we report TFTs based on solution-processed In₂O₃ semiconductors doped with Pr⁴⁺ or Tb⁴⁺, which can effectively improve the NBIS stability. The differences between the Pr⁴⁺-doped In₂O₃ (Pr:In₂O₃) and Tb⁴⁺-doped In₂O₃ (Tb:In₂O₃) are investigated in detail. The undoped In₂O₃ TFTs with different annealing temperatures exhibit poor NBIS stability with serious turn-on voltage shift (ΔV_on). After doping with Pr⁴⁺/Tb⁴⁺, the TFTs show greatly improved NBIS stability. As the annealing temperature increases, the Pr:In₂O₃ TFTs have poorer NBIS stability (ΔV_on are −3.2, −4.8, and −4.8 V for annealing temperature of 300, 350, and 400 °C, respectively), while the Tb:In₂O₃ TFTs have better NBIS stability (ΔV_on are −3.6, −3.6, and −1.2 V for annealing temperature of 300, 350, and 400 ℃, respectively). Further studies reveal that the improvement of the NBIS stability of the Pr⁴⁺/Tb⁴⁺:In₂O₃ TFTs is attributed to the absorption of the illuminated light by the Pr/Tb4fⁿ—O2p⁶ to Pr/Tb 4fⁿ⁺¹—O2p⁵ charge transfer (CT) transition and downconversion of the light to nonradiative transition with a relatively short relaxation time compared to the ionization process of the oxygen vacancies. The higher NBIS stability of Tb:In₂O₃ TFTs compared to Pr:In₂O₃ TFTs is ascribed to the smaller ion radius of Tb⁴⁺ and the lower energy level of Tb 4f⁷ with a isotropic half-full configuration compared to that of Pr 4f¹, which would make it easier for the Tb⁴⁺ to absorb the visible light than the Pr⁴⁺.

Solar-blind ultraviolet (UV) photodetectors based on wide-bandgap oxide semiconductors are highly desirable for environmental monitoring, flame sensing, and secure optical communication. Among them, Ga₂O₃ has attracted extensive attention due to its ultra-wide bandgap and intrinsic solar-blind response; however, its high dark current, weak built-in electric field, and defect-induced instability remain critical challenges, particularly for amorphous films prepared by scalable sputtering processes. Herein, a self-powered solar-blind UV photodetector based on a NiO/Ga₂O₃ heterojunction is demonstrated, in which the oxygen-vacancy concentration and band structure of sputtered Ga₂O₃ are systematically regulated by tailoring the Ar/O₂ sputtering atmosphere. Combined X-ray photoelectron spectroscopy, UV photoelectron spectroscopy, and optical measurements reveal that the variation in oxygen-vacancy concentration simultaneously modulates the Fermi-level position, band-edge alignment, and built-in potential at the NiO/Ga₂O₃ interface. As a result, the optimized heterojunction device exhibits a low dark current, pronounced rectifying behavior, and efficient carrier separation under zero bias, enabling self-powered operation. The photodetector delivers a responsivity of 47 mA W⁻¹, a detectivity of 7.52 × 10¹¹ Jones, and a high rejection ratio exceeding 10⁴ between 254 and 365 nm. Furthermore, stable and high-contrast UV imaging is successfully demonstrated, highlighting the practical applicability of the device. This work provides an effective methodology for modulating defects and band structure in high-performance solar-blind UV photodetectors based on sputtered wide-bandgap oxide heterojunctions.