•The seed layer of AZO film influences the crystal quality and diameter size of ZnO NRs.•Cu2O/ZnO NRs heterojunction is suitable for the self-powder photodetector in violet and blue light.•Cu2O/ZnO NRs based devices show excellent stability and reproducibility of photoresponse.•The device with AZO (0.5%) seed layer exhibits fast response time and high responsivity.The Cu2O films were electrodeposited on ZnO nanorod arrays (NRs) and the Cu2O/ZnO NRs heterojunctions were formed. The optical-electronic response of the heterojunctions was investigated. The diameter size and crystal quality of ZnO NRs were modified by the seed layer. ZnO NRs with good crystal quality were obtained on the 0.5% Al doped ZnO seed layer film (named as AZO (0.5%)). The devices based on the Cu2O/ZnO NRs heterojunction exhibit excellent stability and reproducibility of the self-powered photoresponse properties. The device with AZO (0.5%) seed layer demonstrates the high photoresponsivity of 60–70 mA/W in the violet and blue light with a fast response speed at zero applied bias.Fig. 8(a)The spectral photoresponsivity of the devices with different seed layers at zero bias, and Fig. 8(b) The energy band diagrams of the Cu2O/ZnO NRs heterojunctions based device under zero bias under the UV and visible light illuminations.

Designing a rational structure and developing an efficient fabrication technique for bottom-up devices offer a promising opportunity for achieving high-performance devices. In this work, we studied how Al-doped ZnO (AZO) seed layer films influence the morphology and optical and electrical properties for ZnO aligned nanorod arrays (NRs) and then the performance of ZnO NRs based ultraviolet photodetectors (UV PDs) with Au/ZnO NRs Schottky junctions and p-CuSCN/n-ZnO NRs heterojunctions. The PD with AZO thin film with 0.5 at. % Al doping (named as AZO (0.5%)) exhibited more excellent photoresponse properties than that with pristine ZnO and AZO (1%) thin films. This phenomenon can be ascribed to the good light transmission of the AZO layer, increased density of the NRs, and improved crystallinity of ZnO NRs. The PDs based on CuSCN/ZnO NRs heterojunctions showed good rectification characteristics in the dark and self-powered UV photoresponse properties with excellent stability and reproducibility under low-intensity illumination conditions. A large responsivity located at 365 nm of 22.5 mA/W was achieved for the PD with AZO (0.5%) thin film without applied bias. The internal electric field originated from p-CuSCN/n-ZnO NRs heterojunctions can separate photogenerated carriers in ZnO NRs and drift toward the corresponding electrode.Keywords: AZO films; heterojunctions; Schottky junctions; self-powered photodetector; ZnO nanorods

Cu2O films were electrodeposited on FTO and ZnO thin film substrates under different electrolyte pH. The Cu2O films on FTO substrates have a preferred orientation along the (111) planes for the match between the growing Cu2O film and the FTO substrate at the interface, whereas a transition of the preferred orientation from (100) to (111) occurs for the films on ZnO thin film substrates as electrolyte pH increases. All the Cu2O films show very similar photoluminescence (PL) spectra characteristics with a green emission band, which is related to the inter-band transitions, and a red broad emission band, which is assigned to the defects. The relative weak PL spectra for the films on ZnO thin film substrates can be ascribed to the energy and charge transfer from Cu2O to ZnO. Under light illumination, the Cu2O films on ZnO thin film substrates show the photovoltaic effect, which indicates the formation of Cu2O/ZnO heterojunctions. The photoresponse of the heterojunctions at zero bias voltage shows high sensitivity to visible light illumination, with excellent stability and reproducibility. The photocurrent is larger for the heterojunctions of the Cu2O film deposited at the pH 10.5, which is attributed to the good crystalline quality of the Cu2O film and strong built-in electric field of the ZnO/Cu2O interface.

Eu3+ doped fluorozirconate glass ceramics containing BaCl2 nanocrystals were successfully fabricated by melt quenching method, and their structural and luminous properties were investigated. The existence of BaCl2 nanocrystals in the glass ceramics plays an important role on the improvement of luminescent properties. The emission intensity in glass ceramics was remarkably enhanced, which attributes to the phonon energy decrease by Eu3+ ions into BaCl2 nanocrystals. Meanwhile, the extended average fluorescence decay lifetime from 4.60 ms to 5.42 ms and the decreased Red/Orange ratio and spark splitting of 7F1 energy level also confirmed this view. Additionally, the excitation spectra showed that glass ceramics could be effectively excited by NUV light. The CIE chromaticity coordinates of glass ceramics (GC320) were calculated as (0.611, 0.371), which was close to the NTSC standard values for red (0.67, 0.33). The results suggested that the glass ceramics may be used as potential red phosphors under UV light excitation for white light-emitting diodes.

•The TiO2/PbS(CdS) QDs bulk heterojunction was fabricated by SILAR method.•The additional CdS improved the photoelectric conversion properties.•The CdS modification can reduce trap states and carriers recombination.TiO2/PbS(CdS) quantum dots (QDs) bulk heterojunction has been fabricated by successive ionic layer adsorption and reaction method via alternate deposition of PbS and CdS QDs. In comparison with TiO2/PbS heterojunction, the incident photon to current conversion efficiency was increased almost 50% in the visible region. Meantime, the short-circuit current and open-circuit voltage were enhanced 200% and 35% respectively. The influence mechanism of CdS is related to reduction of trap state density at TiO2/PbS interface and PbS QDs surface by the discussion of the dark current density–voltage curves, the transient photocurrent response curves and the electrochemical impedance spectra spectroscopy (EIS).The figure shows charge transport schematic diagram for TiO2/PbS(CdS) heterojunction. (The red crosses represent the blocked charge transport process.)

•The surface-to-volume ratio of ZnO nanorods decreases with precursor concentration increase.•The decrease of surface-adsorbed O2 and OH− species induces enhanced yellow-green emission band.•The amount decrease for adsorbed O2 and OH− induces narrow width of ZnO nanorods depletion region.•The decrease of surface-to-volume ratio of ZnO nanorods leads to the reduction of RTFM.ZnO nanorods have been fabricated by hydrothermal method with different precursor concentrations. The structural, optical and magnetic properties of ZnO nanorods have been investigated. With the precursor concentration increase, the surface-to-volume ratio of ZnO nanorods decreases. Photoluminescence (PL) spectra of all samples are dominated by the visible emission band related to the defects. PL spectra under different excitation energies and PL excitation (PLE) spectra revealed that yellow-green emission band is related to a transition from a shallow donor level to doubly ionized oxygen vacancy (Vo2+)(Vo2+) and green emission band to the recombination of electrons trapped in single ionized oxygen vacancies (Vo+)(Vo+) with photo-generated holes. With the precursor concentration increase, the decrease of surface-adsorbed O2 and OH− species, as acceptor and donor surface states, induces the reduced non-radiative transition probabilities and enhanced yellow-green emission band. The reduction of room temperature ferromagnetism was observed with the decrease of surface-to-volume ratio of ZnO nanorods.

This study reports a simple method for the synthesis of different size of wurtzite ZnO nanoparticles in assistance of tetraethyl orthosilicate (TEOS). With the increase of the amount of TEOS added, the average size of ZnO nanoparticles was found decreased from ∼14.6 to ∼1.9 nm by characterization of X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The growth of ZnO nanoparticles is proposed to be controlled by the density of the SiO2 chain mesh which is determined by TEOS amount in precursor. Ultraviolet–visible (UV–VIS) absorption and photoluminescence (PL) spectra show both shift to higher energy in cut-off edge and in visible emission bands respectively. The electron transition process in the mechanism of the visible emission shift was described and related to quantum size effect in ZnO nanoparticles.Highlights► The simple synthesis of ZnO nanoparticles was developed in the SiO2 network. ► The average size decreases with the amount increase of TEOS in precursor. ► The visible emission peaks blue shifts with the increase of TEOS amount. ► Quantum size effect has been explained the visible emission band shift.

Si4+-doped BaZr(BO3)2:Eu3+ phosphors are prepared by a conventional solid-state reaction. The influence of Si4+ addition on the charge transfer state of Eu3+-O2− and photoluminescence (PL) properties of BaZr(BO3)2:Eu3+ are discussed. Room temperature PL spectra indicated that efficient emission is obtained by Si doping. Increased values for the peak-peak ratio (PPR) of BaZr(BO3)2:Eu3+ at higher Si doping concentrations implied that the Eu3+ ion is located in a more asymmetric environment in BaZr0.8Si0.2(BO3)2:Eu3+ than in the undoped samples. The Judd-Ofelt parameters Ωλ (λ=2,4) were calculated from the PL data, giving results that were consistent with those from the PPR. The maximum radiative quantum efficiency was achieved at a Si doping concentration of 20 mol%.

A large amount of one-dimensional ZnO nanorods with diameters in 15–50 nm aligned in radial cluster were successfully synthesized by polar polymer polyvinyl alcohol (PVA) as soft-template. The growth of ZnO nanorods was controlled by changing annealing temperature. The evolution of the morphology and microstructure was investigated by scanning electron microscope, transmission electron microscope and X-ray diffraction. It is shown that ZnO nanorods tend to be uniform and the crystallization is gradually improved with the temperature increasing from 400° to 700°. The photoluminescence spectra of products show a strong ultra violet emission and relatively weak defect emissions. The sharp strong emission peak at 354 nm owing to the inter-band transition indicates the extraordinary photoluminescence property of ZnO nanorods.