A solid-state PEDOT:PSS/α-Ga ₂ O ₃ nanorod array/FTO photodetector paves a feasible way to realize high-performance self-powered α-Ga ₂ O ₃ solar-blind UV/visible dual-band photodetection by easy, common and low-cost processes.

Herein, we successfully fabricated an Al-doped α-Ga₂O₃ nanorod array on FTO using the hydrothermal and post-annealing processes. To the best of our knowledge, it is the first time that an Al-doped α-Ga₂O₃ nanorod array on FTO has been realized via a much simpler and cheaper way than that based on metal–organic chemical vapor deposition, magnetron sputtering, molecular beam epitaxy, and pulsed laser deposition. And, a self-powered Al-doped α-Ga₂O₃ nanorod array/FTO photodetector was also realized as a photoanode at 0 V (vs. Ag/AgCl) in a photoelectrochemical (PEC) cell, showing a peak responsivity of 1.46 mA/W at 260 nm. The response speed of the Al-doped device was 0.421 s for rise time, and 0.139 s for decay time under solar-blind UV (260 nm) illumination. Compared with the undoped device, the responsivity of the Al-doped device was ~5.84 times larger, and the response speed was relatively faster. When increasing the biases from 0 V to 1 V, the responsivity, quantum efficiency, and detectivity of the Al-doped device were enhanced from 1.46 mA/W to 2.02 mA/W, from ~0.7% to ~0.96%, and from ~6 × 10⁹ Jones to ~1 × 10¹⁰ Jones, respectively, due to the enlarged depletion region. Therefore, Al doping may provide a route to enhance the self-powered photodetection performance of α-Ga₂O₃ nanorod arrays.

The α-Ga₂O₃ nanorod array is grown on FTO by hydrothermal and annealing processes. And a self-powered PEDOT:PSS/α-Ga₂O₃ nanorod array/FTO (PGF) photodetector has been demonstrated by spin coating PEDOT:PSS on the α-Ga₂O₃ nanorod array. Successfully, the PGF photodetector shows solar-blind UV/visible dual-band photodetection. Our device possesses comparable solar-blind UV responsivity (0.18 mA/W at 235 nm) and much faster response speed (0.102 s) than most of the reported self-powered α-Ga₂O₃ nanorod array solar-blind UV photodetectors. And it presents the featured and distinguished visible band photoresponse with a response speed of 0.136 s at 540 nm. The response time is also much faster than the other non-self-powered β-Ga₂O₃ DUV/visible dual-band photodetectors due to the fast-speed separation of photogenerated carries by the built-in electric field in the depletion regions of PEDOT:PSS/α-Ga₂O₃ heterojunction. The results herein may prove a promising way to realize fast-speed self-powered α-Ga₂O₃ photodetectors with solar-blind UV/visible dual-band photodetection by simple processes for the applications of multiple-target tracking, imaging, machine vision and communication.

Herein, corundum-structured Ga₂O₃ (α-Ga₂O₃) nanorod array/fluorine-doped SnO₂ (FTO) structures have been fabricated by hydrothermal and thermal annealing processes with different precursor concentrations from 0.01 to 0.06 M. The diameter and length of the nanorod arrays are much larger with increasing precursor concentrations due to more nucleation sites and precursor ions participating in the reaction procedures. The optical bandgap decreases from 4.75 to 4.47 eV because of the tensile stress relieving with increasing the precursor concentrations. Based on self-powered photoelectrochemical (PEC) photodetectors, the peak responsivity is improved from ∼0.33 mA W⁻¹ for 0.06 M to ∼1.51 mA W⁻¹ for 0.02 M. Schottky junctions can be formed in PEC cells. More photogenerated carriers can be produced in wider depletion region. From Mott–Schottky plots, the depletion regions become much wider with decreasing the precursor concentrations. Therefore, the enhance responsivity is owing to the wider depletion regions. Due to the reduced possibility of photogenerated holes captured by traps ascribed from fewer green and yellow luminescence defects, smaller charge transfer resistance, and shorter transportation route, the decay time becomes much faster through decreasing the precursor concentrations. Compared with the other self-powered α-Ga₂O₃-nanorod-array-based PEC photodetectors, it shows the fastest response time (decay time of 0.005 s/0.026 s) simply modulated by precursor concentrations for the first time without employing complex precursors, seed layers or special device designs. Compared with other high-responsivity monoclinic Ga₂O₃ (β-Ga₂O₃) self-powered photodetectors, our devices also show comparable response speed with simple control and design. This work provides the realization of fast-speed self-powered Ga₂O₃ based solar-blind ultraviolet photodetectors by simple modulation processes and design, which is a significant guidance for their applications in warnings, imaging, computing, communication and logic circuit, in the future.