Ultraviolet photodetectors (UV PDs) have attracted extensive attention owing to their wide applications, such as optical communication, missile tracking, and fire warning. Wide-bandgap metal-oxide semiconductor materials have become the focus of high-performance UV PD development owing to their unique photoelectric properties and good stability. Compared with other wide-bandgap materials, studies on indium oxide (In2O3)-based photoelectrochemical (PEC) UV PDs are rare. In this work, we explore the photoresponse of In2O3-based PEC UV PDs for the first time. In2O3 microrods (MRs) were synthesized by a hydrothermal method with subsequent annealing. In2O3 MR PEC PDs have good UV photoresponse, showing a high responsivity of 21.19 mA/W and high specific detectivity of 2.03 × 1010 Jones, which surpass most aqueous-type PEC UV PDs. Moreover, In2O3 MR PEC PDs have good multicycle and long-term stability irradiated by 365 nm. Our results prove that In2O3 holds great promise in high-performance PEC UV PDs.

military and daily life. [1] Various widebandgap semiconductors with diverse morphologies [2] and nanostructures, [3] have been developed for SBUV PDs. Recently, photoelectrochemical-type (PEC) PDs have been booming due to the low-cost fabrication, low-quality requirement of materials, good self-powered capability, and high sensitivity. [4] Compared with traditional solid-state SBUV PDs, PEC SBUV PDs not only depend on the internal charge transport of semiconductors but also rely on the charge transfer at the interface between semiconductors and electrolyte, offering more freedom to regulate the photoresponse performance. Several widebandgap semiconductors with various nanostructures, such as Ga 2 O 3 nanorods [5] and AlGaN nanowires, [6] have been investigated for PEC SBUV PDs. However, the corresponding photoresponse is much lower than expected. Several strategies have been proposed to improve the performance of PEC SBUV PDs, such as surface modification of noble metal nanoparticles [6b,c] and the construction of core-shell heterojunctions, [7] which inevitably increase the fabrication cost. Therefore, it is attractive to explore alternative and low-cost strategies for promoting the photoresponse of PEC SBUV PDs.Tin oxide (SnO 2 ) is an n-type wide-bandgap (E g = 3.6 eV) semiconductor with the merits of superior electron transport properties and good stability in the environment, [8] endowing SnO 2 an attractive candidate for gas sensors, [9] electrocatalysts, [10] solar cells, [11] lithium-ion batteries, [12] and SBUV PDs. [13] Traditional solid-state SBUV PDs based on various SnO 2 nanostructures [14] and heterojunctions [15] have been exploited with good performance, certainly demonstrating their potential application in UV PDs. However, PEC SBUV PDs based on individual SnO 2 nanostructures have rarely been investigated. [16] Most studies focus on utilizing the good electron transport properties of SnO 2 to improve the photoresponse of other wide-bandgap semiconductor-based PEC SBUV PDs (such as TiO 2 and ZnO) [17] by constructing heterostructures. Although SnO 2 nanoparticles-based PEC PDs have been investigated, they show poor photoresponse with a low responsivity Tin oxide (SnO 2 ) is an n-type wide-bandgap semiconductor with the merits of superior electron transport properties and good stability, making it an attractive candidate for solar-blind ultraviolet photodetectors (SBUV PDs). However, it is still challenging to design high-performance SnO 2 -based photoelectrochemical (PEC)-type SBUV PDs. In this study, oxygen vacancies (OVs) engineering is proposed to manipulate the photoresponse of SnO 2 nanosheets (NSs) and high-performance SnO 2 -based PEC SBUV PDs are developed. SnO 2 NSs with different OVs are prepared by hydrothermal method with annealing process. PEC PDs consisting of SnO 2 NSs annealed at 550 °C show record high responsivity and specific detectivity of 269.40 mA W −1 and 2.38 × 10 12 Jones at a bias voltage of 0.2 V, respectively, surpassing all aqueous-type PEC UV PDs. OVs simulta...

Ga2O3 is a good candidate for deep ultraviolet photodetectors due to its wide-bandgap, good chemical, and thermal stability. Ga2O3-based photoelectrochemical (PEC) photodetectors attract increasing attention due to the simple fabrication and self-powered capability, but the corresponding photoresponse is still inferior. In this paper, the oxygen vacancy (Vo) engineering towards α-Ga2O3 was proposed to obtain high-performance PEC photodetectors. The α-Ga2O3 nanorods were synthesized by a simple hydrothermal method with an annealding process. The final samples were named as Ga2O3-400, Ga2O3-500, and Ga2O3-600 for annealing at 400, 500, and 600 ℃, respectively. Different annealing temperatures lead to different Vo concentrations in the α-Ga2O3 nanorods. The responsivity is 101.5 mA/W for Ga2O3-400 nanorod film-based PEC photodetectors under 254 nm illumination, which is 1.4 and 4.0 times higher than those of Ga2O3-500 and Ga2O3-600 nanorod film-based PEC photodetectors, respectively. The photoresponse of α-Ga2O3 nanorod film-based PEC photodetectors strongly depends on the Vo concentration and high Vo concentration accelerates the interfacial carrier transfer of Ga2O3-400, enhancing the photoresponse of Ga2O3-400 nanorod film-based PEC photodetectors. Furthermore, the α-Ga2O3 nanorod film-based PEC photodetectors have good multicycle, long-term stability, and repeatability. Our result shows that α-Ga2O3 nanorods have promising applications in deep UV photodetectors.

Two-dimensional (2D) In2Se3 has received considerable attention due to its suitable band gap, good photoresponse, and high stability, making it a good candidate for high-performance photodetectors. Self-powered 2D In2Se3-based photodetectors consisting of heterojunctions usually require a complex fabrication process, hindering their application. In this work, we synthesize 2D In2Se3 nanosheets by an electrochemical exfoliation method and fabricate self-powered In2Se3 photoelectrochemical (PEC) photodetectors by a simple drop-casting method. The self-powered In2Se3 PEC photodetectors show a broadband photoresponse from ultraviolet (365 nm) to near-infrared (850 nm) with a high responsivity of 1.88 mA/W, fast response speed of 1 ms, and good stability, surpassing most 2D material-based PEC photodetectors. Our results demonstrate that self-powered In2Se3 PEC photodetectors hold great promise in next-generation high-performance optoelectronic devices.

Moreover, Se-based PDs show good photoresponse, such as high responsivity, high photoconductivity, fast response, and good environmental stability. [4] Therefore, it can be a good candidate for the preparation of high-performance broadband PDs. Although traditional solid-state Sebased phototransistors and self-powered solid-state Se-based heterojunction-type PDs have been investigated, [3][4][5] there are no reports on high-performance single element material-based self-powered photoelectrochemical (PEC)-type photodetectors (PDs) so far. Recently, PEC-type PDs have attracted increasing attention owing to their unique working mechanisms and advantages, [6] such as a simple fabrication process, low cost, environmental friendliness, and self-powered capability. [7] Several studies have been conducted to explore Se-based PEC PDs. [4b,c] Chen et al. [4b] designed PEC PDs based on liquid exfoliated 2D Se nanosheets, showing a responsivity (R) of 10.45 µA W −1 . Se quantum dots (QDs) were also synthesized and investigated for application in PEC PDs. [4c] However, the photoresponse of Se-based PEC PDs fabricated by the dropcasting method (DC) is poor. The construction of heterojunctions has been applied to improve the optoelectronic properties of Se-based PEC PDs. [4d,e,8] For example, Zhang et al. [4d] constructed a binary heterostructure (Te@Se) of Se-covered Te nanosheets, showing a R value of 432.72 µA W −1 , which is 41 times higher than that of 2D Se nanosheets. [4b] However, the photoresponse performance of Se-based PEC PDs is still much lower than expected. Therefore, it is urgent to develop a simple way to design high-performance Se-based PEC PDs.In this work, in situ grown t-Se microrod array films (IS-Se MAFs) on fluorine-doped tin oxide (FTO) substrates were synthesized by a simple electrodeposition method (Scheme 1a). Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy characterizations demonstrate that IS-Se MAFs have a uniform morphology with dense microrods and scattered nanorods, as well as good crystallinity. Two kinds of photocathodes (IS-Se and DC-Se) were fabricated, and the corresponding photoelectrochemical photoresponse was systematically investigated (Scheme 1b). IS-SeMAFs PEC PDs show good self-powered photodetection performance. Compared with DC-Se PEC PDs, IS-Se MAFs Selenium (Se) is a p-type semiconductor with a narrow bandgap, that holds great potential for application in the field of photodetectors because of its good optical properties. However, the photodetection performance of Sebased photoelectrochemical photodetectors (PEC PDs) fabricated by the drop-casting (DC) method is still far below the expected value. In this work, in situ grown t-Se microrod array films (IS-Se MAFs) are prepared on fluorinedoped tin oxide (FTO) by a simple electrodeposition method at 353 K. PEC PDs consisting of IS-Se MAFs as photocathodes show excellent self-powered photodetection capability ...