Search

The exploration of new red phosphors is important for the development of white light-emitting diodes (w-LEDs), as existing red phosphors exhibit low efficiency and low performance. This work aims to enhance the photoluminescence characteristics of a red-emitting Gd2Zr2O7:Eu3+ phosphor by co-doping with Al3+. Eu3+ single-doped and Eu3+ and Al3+ co-doped Gd2Zr2O7 nanophosphors that could be efficiently pumped by commercial near-UV LED chips were prepared by a modified liquid–solid–solution phase-transfer method. X-ray diffraction data revealed that the synthesized phosphors were well crystallized with single-phase fluorite structure. Scanning electron microscopy images showed that the particle size ranges from 15 to 25 nm. In addition, the optical performance of the samples was characterized by fluorescence spectroscopy and lifetime spectroscopy. The effect of Al3+ on the luminescence performance of the Eu3+-doped Gd2Zr2O7 phosphor was studied in detail. The emission intensity of the Gd1.93Zr1·97O7:Eu3+0.07Al3+0.03 phosphor was found to be 620% stronger than that of the single-doped Eu3+ phosphor. These results unambiguously show that the Gd1.93Zr2-xO7:Eu3+0.07Al3+x phosphors are promising candidates for application in w-LEDs.

Usually, ZnO thin films used in ultraviolet photodetector exhibit good photoresponse property when ultraviolet signal is strong enough. However, due to the high dark current, pure ZnO is insusceptible to weak ultraviolet signal. To address this problem, lithium-doped ZnO (LZO) thin films were prepared using the sol-gel method in this study. Results revealed that the LZO thin film doped with low concentration (2 at.%) had a dark current about 10 times lower than the pure ZnO. In addition, the ultraviolet with a low irradiance of 90 μW/cm2 was used. According to the results of the investigations on the external quantum efficiency and responsivity, the inherent photocurrent generation ability of ZnO was not deteriorated through low concentration lithium doping. LZO thin film doped with 2 at.% exhibited a high sensitivity to weak ultraviolet signal --- the signal-to-noise ratio was enhanced by approximately 10 times compared with that of pure ZnO. This study indicates that LZO thin films with low doping concentration are promising application on weak ultraviolet signal photodetector.

In this paper, the effect of sputtering distance between target and substrate (DTS) on the structural, morphological and optical properties of TiO2 films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that crystallite size and surface morphology were strongly dependent on DTS. The X-ray photoelectron spectroscopy (XPS) results showed that obvious three peaks including C1S, Ti2p and O1s could be clearly observed and the binding energy was 285, 458 and 531 eV, respectively. For each sample, four peaks near 386, 462, 527 and 595 nm in photoluminescence (PL) spectra were observed and originated from intrinsic recombination, F center, F+ center and electrons transferred from 3d Ti3+ states to the deep levels OH−, respectively. Finally, the photoresponse properties of UV detectors based on TiO2 films were analyzed and the TiO2 UV detector prepared at a DTS of 80 mm showed high responsivity of 2.02 × 10−4 A/W and excellent photosensitivity of 32.25, also, exhibited a fast response with a rise time (τr) of 0.98 s and fall time (τf) of 3.14 s.

The recently discovered and prepared honeycomb borophene is one of the many forms of borophene. For the first time, we studied the tribological properties of honeycomb borophene based on first principles and found that it has excellent tribological performance. As a two-dimensional material, honeycomb borophene has potential applications in the field of tribology. Correspondingly, we studied interlaminar charge transfer in several common heterojunctions and then explored its internal friction mechanism. The present work indicts that honeycomb borophene, a new type of two-dimensional material, may help broaden the research field of two-dimensional materials in tribology.

Previous reports found Al-doped ZnO nanosheets were formed at a certain preparation condition, but the formation mechanism was vague. In this work, we prepare sol-gel Al-doped ZnO films, and find that films show the obvious nanorods structure on surface of pure ZnO, but the nanorods changes to nanosheets gradually with rising doping concentration. The formation mechanism of nanosheets is clarified, and the doping concentration dependence of morphology is discussed in this paper. In addition, the photoluminescence spectra of all films appear a series of emissions including the near band edge emission (NBE) at 388 nm and several defect emissions (DE) at 396–499 nm. Previous reports proposed that NBE and DE would rise monotonously or decline monotonously with doping. However, this work reveals that the NBE decreases firstly in the range of low doping concentrations and then improves upon excessive doping concentration, due to crystalline quality and optical energy gap --- this reason is different from traditional explanations. Also, DE at different positions show the different variation trends, without the same increase or the same decrease. At excessive doping concentration, both NBE and DE enhance, illustrating the potential application for the enhanced ultraviolet and white light emitting devices.

In this paper, the AlSb films were successfully prepared by direct-current (DC) magnetron sputtering technology and the deliquescence process and mechanism of AlSb films were investigated, moreover, the function of Cu membrane deposited on AlSb films was simply explored. It suggested that deliquescence processes of films were essentially local deliquescence and further formed some sand holes, ultimately, AlSb films fall off from the quartz glass substrate as increase in contact time between AlSb films and ambient air. Meanwhile, compared to bare AlSb films, Cu deposited on AlSb films could effectively prevent the appearance of sand holes in the specific conditions and the way of annealing treatment further improved the stability of AlSb films.

Mn-doped ZnO (MZO) films were prepared on glass substrates using sol–gel dip-coating technology. The microstructural, morphological, optical and photoelectric properties of MZO films were investigated at different withdrawal speeds (WS: 20, 40, 60 and 80 mm s−1). The X-ray diffraction (XRD) patterns showed that all the films obtained were polycrystalline with a hexagonal structure, and the highest crystallinity of MZO films was observed as films were deposited at 40 mm s−1. The UV-Vis spectra revealed that the average optical transmittance of all samples was over 60% and the energy band gap of films decreased from 3.616 to 3.254 eV with the increase in withdrawal speed. The formed Au/MZO/Au photodetectors (PDs) indicate that a device prepared at 40 mm s−1 shows superior properties both in response speed and detection capability, and the rise time is 1.871 s and fall time is 3.309 s at 365 nm for 3 V bias and the detectivity (D*) reaches ∼1.7 × 1010 Jones. Moreover, the responsivity of PDs is also affected by the distance between Au electrodes and external bias. This research provides a simple way to fabricate the UV PDs based on MZO films with faster response and higher detectivity.

Free-standing BiI3 single-crystal flakes with a rhombohedral appearance and 10–100 µm in thickness were prepared by using physical vapor transport method. The (00l) (l = 3, 6, 9, 12) planes of the as-grown crystal present a distribution of layered structure and approximatively atomically smooth surface with 1.3–1.7 nm step height and roughness average 0.38–0.65 nm. Both planar and coplanar electrode configuration devices for X-ray detection were fabricated with the as-grown BiI3 single crystals and the dark resistivity 5.8–6.4 × 1011 Ω cm and 1.2–1.8 × 1011 Ω cm at room temperature were obtained, respectively. A low dark current or high resistivity for planar device is on account of carrier scattering from the I–Bi–I interlayer van der Waals bonding interface. A high net photocurrent and good sensitivity 1.22–1.36 × 104 µC/Gyair/cm2 under X-ray excitation were also obtained with planar device owing to the uniform electric field distribution and high charge collection efficiency.

We prepared the amorphous selenium (a-Se) thin films via thermal evaporated method with different deposition time, revealing that the increase of deposition time was propitious to improve the quality of a-Se thin films. In detail, the optical gap of a-Se thin films enhanced from 2.08 to 2.15 eV, and the transmittance showed the blue shift of absorption edges with prolonging deposition time. Further, the dark conductivity was analyzed systematically around three main physics issues. (i) The initial dark conductivity was high and decayed with test time. (ii) The dark conductivity showed a dependence of applied electric field. (iii) The dark conductivity decreased with extending deposition time. Moreover, a-Se thin films showed the improved X-ray photoconductivity gain from 1.5 to 3.1 times under exposure dose rate of 14.83 × 10−4 Gy/s of X-radiation, with a rapid photoresponse and a small applied electric field requirement.

Nanocrystalline ZnO thin films with the varied thickness were deposited on glass substrate using sol-gel spin coating method, and the different thickness of samples was achieved via changing the number of layers. X-ray diffraction patterns of samples showed the preferential orientation at (002) planeupon coating with 2 layers and the gradual increase in random orientation with coating up to 6 layers. Scanning electron microscopeimages appeared a few layer interfaces for 4 and 6 layers sample, and atomic force microscope images revealed the larger particle size and rougher surfacewith increasing thickness, which showed the obvious effects on optical properties of samples too. The increased absorption and reduced energy gap were found through deducing transmittance curves of samples. Further, photoluminescence characteristic was measured and revealed that there are the best intrinsic emission in ultraviolet region and lowest defect emissions in visible region for the sample coated with 4 layers.

Base on the first-principles, the energy band and optical properties of TiN thin films were modeled by the materials studio (MS) programm. The energy band, total density of states (DOS), dielectric function, absorption and reflectivity of TiN were studied. The results suggested that the Fermi energy (EF) passes through the energy band with dense distribution of energy levels, moreover, the total density of states crosses the EF, suggested that TiN belongs to metalloid, and determined by electronics in Ti-3d state. Meanwhile, the structure of energy band was affected by pressure, but the influence of temperatures is weak. The reflectivity of TiN to red light (1.63 eV to 1.97 eV) is lower than that of blue light (2.53 eV to 2.75 eV). Moreover, TiN has a higher reflectance in the infrared region, and showed translucent in the visible light region and the static permittivity of TiN is about 39.24 F/m.

The cadmium telluride (CdTe) thin films have been successfully deposited on glass substrates by direct-current (DC) magnetron sputtering method, and the structural, optical and electrical properties of samples were investigated in this paper. X-ray diffraction patterns revealed that all samples exhibited a preferred orientation along (111) plane with cubic phase, and the crystallite size was first increased from 13.6 to 42 nm and then decreased to 31 nm as the sputtering power increased from 10 to 80 W. AFM images showed that surface morphology of CdTe films was affected by the sputtering power and the particles in the films exhibited uniform distribution with obvious RMS roughness (25.9 nm) as the sputtering power was 40 W. Meanwhile, CdTe films appeared a higher transmission properties in the range of 850–1000 nm, and the band gap of films gradually decreased from 1.96 to 1.51 eV and then increased to 1.67 eV as the sputtering power constantly increased. Raman spectrum revealed that the peak at 140 cm−1 exhibited dominant among other peaks, associated to the E mode of Te. The current–voltage (I–V) curves indicated that the conductivity of CdTe films was strongly dependent on the sputtering power and the optimal electrical properties could be achieved at the sputtering power of 40 W.

Titanium nitride (TiN) thin films have been prepared by direct-current reaction magnetron sputtering technique on different substrates (glass and Si) and the influence of substrate and Ar/N2 gas flow ratio on structural, optical and electrical properties of TiN thin films were discussed. X-ray diffraction suggested that with the ratio of Ar/N2 decreasing, the diffraction intensity of (111) plane gradually diminished while (200) plane increased and films on Si substrate exhibited better crystalline quality than glass substrate. Improvement of Ar/N2 ratio is contribute to enhance the deposition rate and the obvious surface roughness were observed when the ratio up to 49. Photoluminescence spectra showed that TiN films on Si substrate showed higher intrinsic emission and lower defect emission. Moreover, the resistivity of TiN films showed obviously decreasing as the flow rate ratio of Ar/N2 increased, especially films on Si substrate.

Cd1−xZnxTe (CZT) films were deposited on ITO substrates at different substrate temperature by repeatedly RF magnetron sputtering with a Cd0.9Zn0.1Te target. The effect of substrate temperature on physical properties of CZT films were systematically investigated. The morphology of CZT films were characterized by atomic force and scanning electron microscopes. The grain size increased and grain boundaries decreased with substrates temperature increasing. XRD studies revealed that as-grown CZT films were polycrystalline with (111) preferential orientation and the crystallization quality was improved with the increase of substrate temperature. Optical analysis of CZT films showed the band gap decreased with the substrate temperature increasing. A1 and A2 detectors were fabricated based on the CZT films deposited at 300 and 400 °C, respectively. The electrical and X-ray response properties at room temperature of two detectors were investigated. The dark resistivity is 1.49 × 108 and 4.26 × 108 Ω cm for A1 and A2 detectors, respectively. The X-ray sensitivity of CZT films deposited at 400 °C was higher than that of CZT films deposited at 300 °C.

In this paper, the dye-sensitized solar cells (DSSCs) were fabricated based on natural dyes extracting from carrot, mulberry, purple cabbage, potato, and grapes. The ultraviolet-visible spectra suggested purple cabbage and mulberry possess better absorption at 300–550 nm. The solar cells using purple cabbage as dye achieved a conversion efficiency of 0.162% with short-circuit photocurrent density (Jsc) of 0.621 mA/cm2, open circuit voltage (Voc) of 0.541 V and fill factor (FF) of 0.484. The Infrared spectra revealed the bond of O H, C C, C O, C H were existed in purple cabbage. Finally, the optimal extraction time of dyes is also presented.

In this work, laser-induced surface recrystallization process was developed to improve the surface properties and device performance of the polycrystalline PbI2 thick films prepared by using close space vapor deposition method. A continuous polycrystalline PbI2 recrystallized layer with a better mechanical strength and reflectivity improved from 2% to 4%–6% was obtained by this recrystallization process for the films with mechanical pretreatment. Other polytypes is absent in the recrystallized layer with the 2H-polytype remaining before and after treatment and obtaining improved electrical and X-ray photoelectric response performance. The pretreatment such as mechanical cutting/polishing and hydrogenation is necessary to lower the non-wetting crystallization behavior during the recrystallization process due to the rough surface state and oxygen contamination.

ZnO thin films on glass substrates were synthesised by sol–gel method with different pretreating temperature. The thermal behaviours of dried gel were firstly tested and found the relationship betw...

The exfoliated CdZnTe (CZT) films were grown on quartz substrates by closed tube physical vapor transport method based on stress mismatch mechanism. The structure and morphology of the exfoliated CZT thick films were characterized by X-ray diffraction and scanning electron microscope. The as-grown CZT films are polycrystalline with (111) preferential orientation and exhibit a dense pyramid surface structure and a thickness of more than 600 μm. The coplanar and planar X-ray detectors were fabricated based on the exfoliated CZT film. The discrepant dark resistivity is 3.17 × 109 and 5.14 × 1010 Ω cm with regard to the coplanar and planar structure detector, respectively. The planar structure detector exhibits higher quantum efficiency at low doses X-ray radiation.

Monolayer non-defect graphene is generally considered to be impermeable. However, recent study has shown that a small amount of molecular hydrogen can permeate it. This process involves the breaking and recombination of bonds, which are closely related to the permeation mode of hydrogen molecules. Here we studied the penetration of hydrogen molecules into three types of graphene (non-defect, Stone-Wales defect and undergoes biaxial tensile) using density functional theory. We found the penetration mode from rings is more favorable for bond breaking although the barrier of vertical mode is lower. In addition, the reduced barrier of Stone-Wales defects is comparable to that of 12% biaxial tensile strain regardless of whether hydrogen molecules permeate in vertical or parallel manner. Our work provides a unique perspective on the breaking of chemical bonds. It also provides a theoretical basis for potential applications of graphene in gas separation and transport.

The transport mechanism of water molecules on the surface of single-layer [Formula: see text]-graphyne is investigated from the first-principles calculations. The result indicates that when water molecules are adsorbed in different stances, their corresponding transport paths are different. When N atoms are doped with sp carbon atoms, the transport pathway of water molecules is opposite to that of intrinsic [Formula: see text]-graphyne, which is due to the charge transfer between atom s. Consequently, this study is conducive to understand the mechanism of nanoscale water transport on the graphyne surface and provides a theoretical basis for exploring the interaction between water and graphyne.

Nano-crystalline ZnO thin films on glass substrates have been prepared by sol–gel method at annealing temperatures of 300–550 °C. Zinc acetate, anhydrous ethanol, and mono-ethanolamine were used as raw materials. The thermal behaviors curves of the dried gel were examined and found that evaporation of solvent and the decomposition of the organics have completed before 250 °C. The effect of thermal annealing on structural and optical properties was investigated. X-ray diffraction patterns showed the gradual increase in orientation of (0 0 2) along c-axis. The transmittance spectra revealed the high transmission (T > 80% above annealing 400 °C) in visible region. The optical band gap (E g) of the samples is in the range from 3.24 to 3.28 eV. The photoluminescence spectra in ultraviolet were studied and found the continuous increased intensity of peaks at 387 and 393 nm respectively from intrinsic emission and near the band edge emission. Surface micrographs was observed by the atomic force microscopy and found the larger grain size and the compacter morphology before 500 °C. However, the excessive annealing temperature at 550 °C deteriorated the structural and optical properties of the samples. The transmittance is still enhanced as rising annealing temperature up to 500 °C which is more attributed to the decrease in grain boundaries and defect concentration. The poor transmission of films annealed at low temperatures is attributed to unsatisfactory crystalline quality. The stable and high transparency (>80%) in the visible region is presented above 400 °C. The UV–Vis transmittance spectra of ZnO thin films at different annealing temperature.

In this paper, 10 types of electrospun polystyrene (PS) nanofibers doped with poly(dibenzo-18-crown-6) (PDB18C6) were prepared and the ones which gave the best recovery of catecholamines – dopamine, norepinephrine and epinephrine from other interfering endogenous substances existing in the plasma matrix based on a previous study were selected. Furthermore, 10 types of composite nanofibers were characterized using scanning electron microscopy (SEM). The SEM results showed that the addition of PDB18C6 resulted in thicker nanofibers with rough surfaces. Furthermore, it was found that increases in the proportion of PS used led to higher mean fiber diameters (200 to 3000 nm). Batch adsorption experiments were conducted to evaluate the optimal composite nanofibers, which act as an adsorbent for selective extraction of catecholamines. At pH 7.5, composite nanofibers No. 10 (20% PS–5% PDB18C6 = 5 : 2, v/v) can improve the extraction efficiency of the catecholamines in plasma with high reproducibility. In comparison with discrete crown ether modified nanofibers, the PDB18C6 functionalized nanofibers offered a polymer backbone to solve the problem of solubility in most solvents for crown ether monomers. Therefore, PDB18C6 functionalized nanofibers increased the complexing properties more than crown ether monomers. Furthermore, electrospinning was shown to be a very versatile tool to prepare PDB18C6 functional polymer adsorbents for the selective recovery of plasma catecholamines.

Cd1−x Zn x Te (CZT) multilayer films were repeatedly deposited by using RF magnetron sputtering with a Cd0.9Zn0.1Te crystal target. The morphological, structural and optical properties of the CZT multilayer films were characterized. The thickness of the CZT films increases from 1360 to 9230 nm with the increase of the repeated deposition cycles. It is found that the mismatching of the thermal stress between the film and substrate was eliminated by repeated deposition, resulting in an improved adhesion and crystalline quality, larger grain size and decreased microvoids. X-ray diffraction patterns show that the polycrystalline structure CZT films with (111) plane preferred orientation was obtained. The band gap of the CZT films decreases from 1.517 to 1.500 eV resulting from Zinc loss during the repeated deposition and anneal. The density of the disordered state was decreased with the increasing of deposition layers.

In this letter, we report a successful facile growth of freestanding single crystals PbI 2 (FSC-PbI 2 ) film via hydrothermal method without additives. The properties of samples were investigated by SEM, X-ray diffraction and UV–vis spectroscopy. The result shows that FSC-PbI 2 film is a wide band gap semiconductor material (2.38 eV) with 2H type. Moreover, the FSC-PbI 2 film based photodetector was also fabricated, and the photodetector respond to x-ray incident light with a fast, repeatable and stable response characterized by a reasonable response and decay times (0.26 s and 0.43 s, respectively). These results substantiate the potential of FSC-PbI 2 film as a candidate material in optoelectronic applications.

In this work we report the dark current, photocurrent and carrier transport properties of the x-ray detector based on lead iodide (PbI2) crystal. The detectors were built with two orthogonal directions configuration as the bias electric field parallel to the crystallographic c-axis E//c and perpendicular to the c-axis E⊥c. It presents the electrical anisotropy including resistivity, dark current, carrier transport and x-ray induced photoelectricity properties with considering the configuration of bias field and c-axis. A mechanism of carrier scattering effect from anisotropic lattice structure, dislocation and stacking fault could be mainly responsible for this anisotropy property in PbI2 crystal. All the results indicate that the crystal orientation will be taken into account when we design and fabricate the x-ray detectors based on PbI2 crystals or films.

In this work, we report on the results of the electrical behavior of coplanar electrode structure X-ray detector based on PbI2 crystal. The detector with coplanar electrode similar to the Van der Pauw structure instead of conventional planar structure can partly reduce the influence of trapping effect to charge carrier transport along the $c$ -axis. According to the configuration, four operating modes of the detector were thoroughly studied. Several novel results, such as the negative polarity dark current and photocurrent under zero bias voltage, orientation polarization, short relaxation time of steady-state surface leakage current and fast photocurrent response are obtained by this kind of coplanar structure configuration. The detector has the potential to be developed as a solid state X-ray dosimeter in the medical radiation environment, providing a high sensitivity and good adaptability under positive or negative bias voltage.

Large-area and high-crystallinity CdZnTe (CZT) thick films are grown by physical vapor transport and vacuum thermal evaporation (PVT-VTE) hybrid method. The structure, morphology and composition of which are characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The as-grown CZT thick films are polycrystalline with (111) preferential orientation, which has a dense pyramid surface structure and a thickness of 590 μm. An 8 × 8 array pixilated X-ray detector is fabricated based on the CZT thick film. The average dark resistivity of 8 pixels on the detector diagonal is up to 3.33 × 1011 Ω cm. The estimated mobility-lifetime product of the CZT array detector is 0.72 × 10−2 cm2V−1. Film structure makes the corresponding detector reduce the influence of trapping effect on the charge carrier transport along the grain growth direction, which shows a short relaxation time and fast photocurrent response. The results demonstrate that the CZT thick film based array detector has high resistivity and sensitivity, and the potential to develop X-ray detection and imaging device under room temperature environment.

ZnO films prepared by sol–gel method and the ultraviolet detectors based on this material have been investigated in this paper. X-ray diffraction (XRD) patterns showed ZnO films present hexagonal wurtzite structure with a preferential orientation of (002) plane, and the crystallite size of films gradually increased from 44.3 to 54.8 nm as the annealing temperature increased from 400 to 600 °C. Ultraviolet–visible (UV–Vis) spectra indicated that the optical band gap decreases gradually with the increase of annealing temperature, and the minimum band gap is 3.06 eV at 600 °C. Photoluminescence (PL) spectra revealed that increasing annealing temperature can significantly reduce the defects and improve the crystallinity. Finally, gold (Au) coplanar interdigital electrodes were deposited on ZnO film surface and used to fabricate the ultraviolet photodetectors. The response performance of the devices improved as the annealing temperature of ZnO films increased, and the fastest response speed with a rise time of 4.172 s and a fall time of 11.012 s was obtained.

Graphene is an excellent material, which can be used in aerospace field. However, it was reported that when graphene works in an oxygen-rich environment, its surface inevitably absorbs oxygen atoms. And oxygen atoms are doped when graphene has defects. In this study, we investigate the effect of adsorption and doping of oxygen atoms on the properties of graphene using first-principles calculations. We found that the adsorption of single oxygen atom can only change the position of Dirac point. However, the adsorption of multiple oxygen atoms may lead to band gaps. Meanwhile, when graphene has defects, oxygen atoms can repair its lattice. But oxygen atoms also localize some electrons, giving graphene a larger band gap than pure defective graphene. This study is helpful to evaluate the properties of graphene in an oxygen-rich environment. At the same time, it has certain significance for the application of graphene in band gap engineering.

Cadmium telluride (CdTe) films were deposited on glass substrates by direct current (DC) magnetron sputtering, and the effect of substrate-target distance (Dts) on properties of the CdTe films was investigated by observations of X-ray diffraction (XRD) patterns, atomic force microscopy (AFM), UV-VIS spectra, optical microscopy, and the Hall-effect measurement system. XRD analysis indicated that all samples exhibited a preferred orientation along the (111) plane, corresponding to the zinc blende structure, and films prepared using Dts of 4 cm demonstrated better crystallinity than the others. AFM studies revealed that surface morphologies of the CdTe films were strongly dependent on Dts, and revealed a large average grain size of 35.25 nm and a high root mean square (RMS) roughness value of 9.66 nm for films fabricated using Dts of 4 cm. UV-VIS spectra suggested the energy band gap (Eg) initially decreased from 1.5 to 1.45 eV, then increased to 1.68 eV as Dts increased from 3.5 to 5 cm. The Hall-effect measurement system revealed that CdTe films prepared with a Dts of 4 cm exhibited optimal electrical properties, and the resistivity, carrier mobility, and carrier concentration were determined to be 2.3 &times, 105 Ω∙cm, 6.41 cm2∙V&minus, 1∙S&minus, 1, and 4.22 &times, 1012 cm&minus, 3, respectively.

Titanium nitride (TiN) films were successfully deposited on different substrates (glass, SiO2 and Si) by direct-current (DC) reaction magnetron sputtering technique, and the structural, optical and electrical properties of samples were investigated. X-ray diffraction patterns showed the films deposited on Si substrates exhibit best crystallinity with a growth preferred orientation of (200) plane. Atomic force microscopy images revealed the films deposited on Si substrates exhibit best uniform distribution of grain size. Raman spectra indicated the Raman shifts of films on SiO2 and Si substrates moved towards higher frequency compared to films on glass substrates. Reflectance spectra suggested that the films deposited on Si substrates show highest reflectance in the infrared region and reached 0.98 at 900 nm. The films deposited on Si substrates presented the lowest resistivity of 50 µΩ cm.

The natural dyes were successfully extracted from spinach, pitaya pericarp, orange peel, ginkgo leaf, purple cabbage and carrot, and then fabricated a dye-sensitized solar cells (DSSCs). It suggested that the absorption properties of natural dyes were strongly dependent on the types and concentration of pigments, and the purple cabbage exhibited an obvious absorption at 317 nm. Meanwhile, a higher conversion efficiency of 0.157% was obtained as the DSSCs were prepared by using purple cabbage, but the DSSCs showed a poor performance when the carrot was used as natural dyes, just achieved 0.01%. FTIR spectra revealed that purple cabbage showed a better adsorption properties between TiO2 films and dyes than carrot. The dipping time was further investigated and proved that an optimal dipping time was 6 min, the DSSCs using purple cabbage could achieve 0.146% in photoelectric conversion efficiency.

We report a controllable, economical and rapid preparation of amorphous selenium (a-Se) thick films by using e-beam evaporation technique. Characterization including X-ray diffraction, Raman and FTIR spectroscopy confirm the amorphous nature of the as-grown films. The films in thickness as high as 267 µm were obtained with a deposition rate of 2.11–2.3 µm/min. A Raman shift peak at 252.4 cm −1 and the absorption of the vibration band at 487.9 and 737.7 cm −1 in FTIR spectra are related to the disordered Se chains and Se 8 rings assigned to a-Se. All the results indicate that the e-beam evaporation is a promising technique for a-Se films fabrication.

For ZnO, doping transition metal is one of the powerful tools to improve its photoelectric performance. In this study, Mn-doped ZnO thin films with various thickness and different doping concentration were synthesized by low cost sol-gel method. We systematically investigated structural and optical properties of Mn-doped ZnO with different concentrations and film thickness. Research showed that with the increase of Mn doping concentration, the crystallization of ZnO decreased, and the preferred orientation was weakened. Moreover, the ultraviolet–visible (UV–Vis) absorption coefficient rose as the energy gap (Eg) decreases and Urbach energy (EU) increases). In the intrinsic emission region below 380 nm and in the defect emission region of 440–600 nm, Mn-doped 1.5% ZnO showed the strongest emission, then the excessive doping would reduce photoluminescence of ZnO. However, in the defect emissions region of 380–440 nm, pure ZnO showed highest emission that decreased gradually with the increase doping concentration. Meanwhile, as the increase of film thickness, the crystallization properties of ZnO were improved, but there were more cracks which resulted in the decrease of UV–vis absorption coefficient, the decrease of Eg and the increase of EU). Meanwhile, the intrinsic emission enhanced and the defect emissions decreased.

Well-aligned ZnO nanorods (NRs) arrays were grown on ZnO seed layer/ITO substrate using chemical bath deposition (CBD) technique and then fabricating ultraviolet (UV) photodetectors (PDs). The effect of precursor concentration of sols on the properties of ZnO seed layer was investigated, and indicated that the crystallinity and growth orientation of samples depend significantly on precursor concentration. ZnO NRs deposited on seed layer exhibit hexagonal wurtzite structure and found that changing the concentration not only affects seed layer, but also influence the rods growth, making it possible to improve the aspect ratio and crystallinity of ZnO NRs. Moreover, the performance of PDs was further discussed and suggested that the maximum signal-to-noise ratio (SNR) and sensitivity (S) of PDs are 67 dB and 2348, when the concentration is 0.5 mol/L, also the shortest rise time of 0.993 s and fall time of 2.036 s can be obtained in such preparation conditions, which is related to larger aspect ratio and higher crystal quality of ZnO NRs. The fabricated UV PDs with high performance are helpful to its application in ultraviolet astronomy, fire detection, especially in military fields, and also are promising for large-scale production.

The performance of diamond is usually closely related to the work environment. However, many researches focus on the relationship between non-doped or hydrogen-doped surfaces and the environment. We investigate the adsorption of N2 and water on non-doped and nitrogen-doped surface using first-principles calculations. The results show that, nitrogen-doped surface can inhibit the spin polarization after adsorption of water, although weak covalent chemical adsorption also occurs on the nitrogen-doped surface. However, the spin polarization phenomenon is obvious when nitrogen is adsorbed perpendicular to the nitrogen-doped surface, although only physical adsorption exists between nitrogen and two kinds of surface. Our results demonstrate the electron spin stability of nitrogen-doped diamonds in humid environments, which is helpful for application of diamond in electron spin devices. In addition, our results provide a microscopic description of the adsorption of N2 and water on non-doped surface, which is helpful for studying the conductivity of diamond in air.

In this work, we prepared the thermal evaporated amorphous selenium (a-Se) thin films with different evaporation time at low vacuum degree 10-2 Pa. The results showed a-Se thin films were easier to be crystallized with prolonging evaporation time. Also, the transmittance absorption edges of a-Se thin films showed a blue shift with the enhanced optical energy gap from 2.08 eV to 2.15 eV. Further, the dark current was found to depend on energy gap, and became lower as extending evaporation time. Moreover, a-Se thin films showed the improved X-ray photocurrent gain, with a rapid photoresponse and a small applied voltage requirement. Overall, this work revealed that the increase of evaporation time led to better deposition quality of thin films, enhancing energy gap and X-ray photoresponse, but thin films were not able to resist to higher temperature anymore.

The dye-sensitized solar cells (DSSCs) have been fabricated by using a series of natural dyes extracted from euonymus japonicus and purple plants. The optical characteristics and chemical structure of dyes were investigated by UV-visible spectroscopy and Fourier infrared spectroscopy. It is found that the absorption of sunlight and bonding performance to TiO2 electrode of dyes had significantly effects on the conversion efficiency of solar cells. The results show the cells using blueberry as sensitizer achieved best conversion efficiency of 0.218%, attributed to its strong absorption and excellent bonding to the TiO2 electrode, correspondingly, the short-circuit photocurrent density ([Formula: see text] and open-circuit voltage ([Formula: see text] were 1.3[Formula: see text]mA/cm2 and 430[Formula: see text]mV, respectively.

Titanium dioxide (TiO2) films have been prepared by DC reaction magnetron sputtering technique on different substrates (glass, SiO2, platinum electrode-Pt, Silicon-Si). X-ray diffraction (XRD) patterns showed that all TiO2 films were grown along the preferred orientation of (110) plane. Samples on Si and Pt substrates are almost monophasic rutile, however, samples on glass and SiO2 substrates accompanied by a weak anatase structure. Atomic force microscopy (AFM) images revealed uniform grain distribution except for films on Pt substrates. Photoluminescence (PL) spectra showed obvious intrinsic emission band, but films on glass was accompanied by a distinct defect luminescence region. Raman spectroscopy suggested that all samples moved to high wavenumbers and films on glass moved obviously.

The performance of dye-sensitized solar cells (DSSC) depends strongly on the electrolyte. In this paper, the electrolytes with various solvents and different potassium iodide (KI) & iodine (I2) concentration were prepared and their influence on the DSSC performance were investigated. The results revealed DSSC with electrolyte prepared by organic solvent show better performance than that of inorganic solvent. Meanwhile, the increasing of KI concentration from 0.1 to 0.6 mol/L can effectively improve the short-circuit current density (Jsc) from 0 2, correspondingly, the DSSC conversion efficiency (η) increased from 0.04% to 0.11%. On the other hand, the Jsc and η of DSSC increased firstly then decreased with the I2 concentration raised from 0.025 mol/L to 0.125 mol/L. It is worth to notice that the open-circuit voltage (Voc) of DSSC is almost unchanged with the concentration of KI and I2. In this paper, the best performance DSSC (Jsc=0.87 mA/cm2, Voc=0.57 mV, η=0.23%) can be obtained with electrolyte at a KI and I2 concentration of 0.6 mol/L and 0.075 mol/L respectively. Finally, the electrolytes used water and mixture of acetonitrile & ethylene glycol as solvents showed the latter presented better stability after setting at room temperature for 72 hours.

The ZnO thin films have been prepared by sol-gel method at different annealing temperatures and aging time. The structural properties of ZnO thin films were investigated by X-ray diffraction (XRD) patterns and atomic force microscope (AFM) images. The results indicated that the film possess a hexagonal wurtzite structure with preferred orientation along the (002) direction. The crystalline quality of films improved with increasing post-annealing temperature, while gradually worsened with prolonging aging time. The optical properties of ZnO thin films were studied by the ultra-violet transmittance (UV-Vis) and photoluminescence (PL) spectra. The variations of UV-Vis transmittance and energy gap accorded well with the tendency presented in XRD patterns and AFM images. The PL spectra appeared the apparent ultraviolet emission and visible emissions. As the annealing temperature increased, the ultraviolet and visible emissions of films enhanced and decreased respectively. However, as the sol aging time prolonged, the PL emission presented an opposite tendency.

A promising flexible X-ray detector based on inorganic semiconductor PbI2 crystal is reported. The sliced crystals mechanically cleaved from an as-grown PbI2 crystal act as the absorber directly converting the impinging X-ray photons to electron hole pairs. Due to the ductile feature of the PbI2 crystal, the detector can be operated under a highly curved state with the strain on the top surface up to 1.03% and still maintaining effective detection performance. The stable photocurrent and fast response were obtained with the detector repeated bending to a strain of 1.03% for 100 cycles. This work presents an approach for developing efficient and cost-effective PbI2-based flexible X-ray detector. Photocurrent responses of the flexible PbI2 X-ray detector with the strain on the top surface up to 1.03% proposed in this work with the cross sectional structure and curved detector photograph as insets. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

ZnO thin films have been prepared by sol–gel method in this paper. Zinc acetate, ethanol and mono-ethanolamine (MEA) were used as a metal precursor, solvent and stabilizer, respectively. The structural and optical properties of ZnO thin films were investigated and found to be strongly dependent on the annealing temperature. X-ray diffraction patterns revealed that as the annealing temperature increased, the crystalline quality of the samples became better. The atomic force microscope images of the samples show larger and compact grains at higher heat-treating temperature. The ultraviolet–visible transmittance spectra indicated that as the temperature increased, the transmittance improved and the energy gap became larger (from 3.11[Formula: see text]eV at 400[Formula: see text]C to 3.22[Formula: see text]eV at 500[Formula: see text]C). The photoluminescence spectra presented a variety of emission peaks, two strong peaks at 390[Formula: see text]nm and 469[Formula: see text]nm, respectively, from the intrinsic emission and point defects, and the intensity of these peaks decreased with the increase of temperature.