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Efficient electron extraction and transport are crucial for high-performance perovskite devices. Herein, an anion–cation synergistic doping strategy is adopted on the electron transport layer of the CH3NH3PbCl3-based photodetector. The cation Zn2+ doping decreases the oxygen vacancies and suppresses carrier recombination. In the meantime, the anion CH3COO− doping controls the longitudinal dimension and accelerates electron transport. On this basis, the comprehensive performances of the photodetector are significantly improved. Impressively, the device responds rapidly to the UVA waveband with a peak responsivity of 70.57 mA W−1 and a switching ratio exceeding 104 in self-powered mode. In contrast, the corresponding values are only 8.02 mA W−1 and 870 in the pristine device, respectively. Moreover, the peak detectivity is up to 1.21 × 1012 Jones under zero bias. Benefiting from these encouraging properties, the photodetector reveals excellent imaging capacity and a high-resolution optical image has been achieved. These results demonstrate that anion–cation synergistic doping is a simple but effective strategy to improve the electron extraction and transport in perovskite devices. [ABSTRACT FROM AUTHOR]

Broadband photodetectors are essential for military and civilian applications. Metal oxides have been widely investigated as photodetectors due to their facile synthesis, low cost and good stability. However, the inherent wide-bandgap allows them to mainly absorb light in the ultraviolet (UV) region, limiting their application in broadband photodetectors. Herein, a self-powered ultraviolet-visible-near infrared (UV-Vis-NIR) photodetector based on β-Bi2O3 nanoparticles is reported, owing to the intrinsic defects introduced through low-temperature thermal oxidation of bismuth (Bi), which induces light absorption in the UV-Vis-NIR region. Moreover, the device exhibits high-efficiency detection performance in the UV (365 nm) to NIR (850 nm) region, especially with a high responsivity of 29.92 mA W−1, a high specific detectivity of 7.46 × 1010 Jones and a fast response time of 20/70 ms under light illumination with a wavelength of 365 nm. These results demonstrate that β-Bi2O3 nanoparticles are promising for high-efficiency broadband photodetector applications. This work also opens up a new strategy for constructing broadband photodetectors based on metal oxides. [ABSTRACT FROM AUTHOR]

A GaOOH/Ga2O3 heterojunction was obtained by a one-step annealing treatment at a certain temperature. The solar blind photoresponse performance of the GaOOH/Ga2O3 heterojunction was characterized through photoelectrochemical detectors, providing a simple and effective method for pure solar-blind ultraviolet detection. The results showed that the maximum responsivity of the α-GaOOH/α-Ga2O3 heterojunction detector is 0.29 mA W−1 at 250 nm, which is 370% and 145% higher than that of the α-GaOOH and α-Ga2O3 detectors, respectively. The calculated solar-blind/visible detection ratio and light-to-dark current ratio of the detector are also significantly improved compared with the α-Ga2O3 and α-GaOOH detectors, reflecting better pure solar-blind ultraviolet detection performance. The photoresponse mechanism has been studied systemically. [ABSTRACT FROM AUTHOR]

Ag nanoparticles (NPs) have been successfully deposited onto TiO2 nanotubes (NTs) via a photochemical method and ZnS layer was further fabricated on the surface of the TiO2/Ag NTs at room temperature. The morphology, composition and structure of the as-prepared samples were analyzed. A self-powered UV photodetector (UVPD) based on the TiO2/Ag/ZnS NTs has been constructed. When exposed to UV light, the TiO2/Ag/ZnS NTs UVPD manifests a higher photocurrent density than that of the TiO2 and TiO2/Ag NTs UVPDs at a bias of zero V. The TiO2/Ag/ZnS NTs UVPD also reveals a splendid linear optical signal response. Meanwhile, it is noteworthy that the TiO2/Ag/ZnS NTs UVPD has excellent stability and repeatability, and the rise time and decay time are 0.16 s and 0.18 s, respectively. Moreover, a possible UV detection mechanism of the TiO2/Ag/ZnS NTs UVPD is proposed. [ABSTRACT FROM AUTHOR]

A novel photoelectrochemical self-powered detector using a newly designed counter electrode as the light-receiving surface is applied to a hydrothermally synthesized α-Ga2O3 nanorod array to realize the detection of solar-blind ultraviolet light with wavelengths below 300 nm and fast response (rise time of 0.076 s and decay time of 0.056 s). [ABSTRACT FROM AUTHOR]

PbSe nanotubes (NTs) were synthesized through a low cost, facile and green hydrothermal route in combination with the assistance of ascorbic acid. In the hydrothermal reaction process, Se nanowires were not only used as templates, but also as a Se ion source to provide Se precursors for the growth of PbSe NTs. The prepared tubular crystals with a cubic structure have a length of 1–6 μm and an average diameter of ∼120 nm. Experimental results show that the amount of ascorbic acid and Pb2+ concentration play important roles in the formation of PbSe NTs, and a possible growth mechanism of PbSe NTs has also been presented. Additionally, the photocatalytic activity of the PbSe NTs was investigated and the results establish that PbSe NTs, in the presence of H2O2, showed a high photodegradation efficiency for methylene blue (MB). A probable photocatalytic mechanism for PbSe NTs is also discussed. [ABSTRACT FROM AUTHOR]

A simple two-step hydrothermal method was used to successfully fabricate a well-grown β-Ga2O3 microrod array from GaOOH on a Si (100) substrate without other heterogeneous layers, to overcome the relatively large surface energy. Different hydrothermal conditions were used to investigate the growth mechanism of the β-Ga2O3/GaOOH microrod array on the silicon substrate. Most significantly, the key role of ethanol in the first-step hydrothermal solution is discussed in light of the change in the adsorption of growing nuclei at the solid–liquid interface. [ABSTRACT FROM AUTHOR]

β-Ga2O3 films have been obtained by thermal annealing of amorphous thin films that were deposited by radio frequency magnetron sputtering. The influence of deposition pressure on the properties of the β-Ga2O3 films was investigated. The structural and optical properties of the β-Ga2O3 films were evaluated using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and optical spectrophotometric measurements. The full width at half maximum of β-Ga2O3 (600) X-ray diffraction peaks decreased firstly and then increased with increasing deposition pressure. A similar variation tendency was observed for the optical band gap of the β-Ga2O3 films. The reasons were attributed to joint action of the atoms' diffusion ability on the surface and oxygen partial pressure with deposition pressure. With increasing pressure, sputtered target species collided more and lacked energy to diffuse leading to poorly crystallized films. With high deposition pressure, oxygen partial pressure also increased in the deposition chamber, thus crystalline quality was improved due to the decrease in oxygen vacancies in the film, which was confirmed by investigating O 1s and Ga 3d core levels using X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

n-ZnO nanorods/p-Si heterojunctions with and without an AlN buffer layer were grown. The ultraviolet luminescence of the ZnO nanorods was greatly enhanced through introducing an AlN buffer layer, and this can be attributed to an improvement in the ZnO nanorod crystallinity, and confinement effects from the AlN potential barrier layer. [ABSTRACT FROM AUTHOR]

Self-assembly of two-dimensional (2D) nanosheets and one-dimensional (1D) nanorods into three-dimensional (3D) double-sided comb-like ZnO nanostructures has been successfully performed via a simple one-step hydrothermal method on Si and ITO substrates. It is found that the thickness of the ZnO seeds plays a vital role in the formation of 3D double-sided comb-like ZnO. [ABSTRACT FROM AUTHOR]

A room temperature successive ionic layer adsorption and reaction (SILAR) method is introduced for fabricating quantum dots-on-wide bandgap semiconductors. Detailed exploration of how SILAR begins and proceeds is performed by analyzing changes in the electronic structure of related elements at interfaces by X-ray photoelectric spectroscopy, together with characterization of optical properties and X-ray diffraction. The distribution of PbS QDs on ZnO, which is critical for optoelectrical applications of PbS with a large dielectric constant, shows a close relationship with the dipping order. A successively deposited PbS QDs layer is obtained when the sample is first immersed in Na2S solution. This is reasonable because the initial formation of different chemical bonds on ZnO nanorods is closely related to dangling bonds and defect states on surfaces. Most importantly, dipping order also affects their optoelectrical characteristics greatly, which can be explained by the heterojunction energy band structure related to the interface. The formation mechanism for PbS QDs on ZnO is confirmed by the fact that the photovoltaic diode device performance is closely related to the dipping order. Our atomic-scale understanding emphasises the fundamental role of surface chemistry in the structure and tuning of optoelectrical properties, and consequently in devices. [ABSTRACT FROM AUTHOR]

The potential applications of quantum dots on wide band gap semiconductor structures in flexible and large-scale optoelectronics demand fundamental analysis of their tunable growth. Herein, PbS quantum dots (＜5 nm) on a ZnO heterostructure are formed by a successive ionic layer adsorption and reaction method. Well distributed PbS quantum dots on ZnO are achieved just by changing the solvent of Pb(NO3)2 and analyzed from the view of solvent-related interaction and adhesion between a hydrophobic substrate and self-assembled layers. This solvent-related distribution of PbS quantum dots on ZnO is confirmed by scanning electron microscopy and transmission electron microscopy, which shows that a fine distribution of PbS quantum dots on ZnO is feasible by using more ethanol in the solvent of Pb(NO3)2. With the aim towards tunable growth of a PbS on ZnO heterostructure, the effects of concentration and dipping times on the size and structure of PbS quantum dots are also explored, which demonstrates that the size of quantum dots is mainly controlled in the thermodynamic domain. Meanwhile, the stoichiometric ratio of Pb and S can also be tuned by changing the dipping times. Most significantly, their optical and electrical properties also show an obvious solvent-related characteristic, which provides another key factor for the potential fabrication and application of quantum dot based devices. [ABSTRACT FROM AUTHOR]

Recently, significant progress has been achieved in paper electronics due to their potential technological applications in rollup displays, wearable devices and smart cards. However, it is still a challenge to efficiently form suitable structured materials on paper substrates due to their porous and rough surface. In this research, ZnO pomegranates composed of 8 nm ZnO nanodots, have been successively fabricated on a pencil drawn graphite-on-paper substrate by an eco-friendly and cost effective solvothermal method. Most significantly, this solution grown photoconductive photodetector shows good device performances with spectrum responsivity to ultraviolet light of 0.06 A W−1 and a quick response time of 4.3 s. Systematic analysis shows that the interface-related energy boundary modulation within ZnO pomegranates may facilitate the separation of photo-induced carriers, eventually resulting in its low dark current and quick response. Meanwhile, this structure designing strategy can be utilized for the future fabrication of high performance paper electronics with other materials. Besides, due to the firm attachment of ZnO pomegranates on the substrate, caused by the introduction of ethanol during the solvothermal growth process and ultrasonic vibration during the formation of the ZnO seed layer, this device is also a highly flexible and rolled-up photodetector with good reversible characteristics and steady performance towards bending deformations and irradiation degradation. [ABSTRACT FROM AUTHOR]

Among the two-dimensional (2D) Bi 2 O 2 X (X = S, Se, and Te) series, Bi 2 O 2 Te has the smallest effective mass and the highest carrier mobility. However, Bi 2 O 2 Te has rarely been investigated, most likely due to the lack of feasible methods to synthesize 2D Bi 2 O 2 Te. Herein, 2D Bi 2 O 2 Te nanosheets are successfully synthesized by low-temperature oxidation of Bi 2 Te 3 nanosheets synthesized using a solvothermal method. The performance of a quasi-solid-state photoelectrochemical-type (PEC-type) photodetector based on 2D Bi 2 O 2 Te nanosheets is systematically investigated. Remarkably, the device has a high responsivity of 20.5 mA W -1 (zero bias) and fast rise/fall times of 6/90 ms under 365 nm illumination, which is superior to the majority of PEC-type photodetectors based on bismuth-based compounds. More importantly, due to the strong anisotropy of 2D Bi 2 O 2 Te nanosheets, the device achieves a dichroic ratio as high as 52, which belongs to the state-of-the-art polarized photodetectors. Besides, the capacity of 2D Bi 2 O 2 Te for high-resolution polarization imaging is demonstrated. This work provides a promising strategy for the synthesis of 2D Bi 2 O 2 Te nanosheets to fabricate a high-performance and polarization-sensitive photodetector.