Search

CsPbBr3 exhibits strong green emission, but its toxicity limits its widespread application. Lead-free perovskites exhibit excellent optoelectronic properties while eliminating the toxicity of lead; at the same time, doping substitution is an effective means to further optimize the optoelectronic performance of perovskites. In this work, zinc(II) is chosen to achieve heterovalent substitution in the copper(I) based perovskite Cs3Cu2Cl5 and obtain strong green luminescence. The photoluminescence quantum yield (PLQY) reached 70.19% at an optimal doping concentration, which is twice the PLQY of undoped Cs3Cu2Cl5 and much higher than that of most doped lead-free perovskites. Furthermore, a white light emitting diode (WLED) was fabricated with doped Cs3Cu2Cl5:0.20 Zn2+ as a green phosphor, commercial blue phosphor Sr(PO4)Cl:Eu+, and commercial red phosphor CaAlSiN3:Eu2+. The color rendering index (CRI) is 95.8, while the correlated color temperature (CCT) is 4573 K, which is much better than that of the WLED fabricated with CsPbBr3. This research provides important guidance on the fabrication of green light emission Zn-doped Cs3Cu2Cl5 instead of toxic CsPbBr3 and has potential in WLED lighting. [ABSTRACT FROM AUTHOR]

A novel Mn2+ doped ScTaO4 phosphor was synthesized through a high temperature solid state method and its photoluminescence properties were systematically investigated. The ScTaO4:Mn2+ phosphor exhibited two emission bands centered at 478 nm and 661 nm under UV excitation, attributed to the self-activated emission of the host and the 4T1 → 6A1 transition emission from doped Mn2+ ions, respectively. Through optimizing the concentration of doped Mn2+ ions, white light emission was achieved. Meanwhile, the temperature-dependent luminescence spectra of the ScTaO4:Mn2+ phosphor (in the range from 298 K to 523 K) revealed significantly different thermal quenching behaviors between the host and Mn2+ ions, which cause a notable change in the fluorescence intensity ratio of the host versus Mn2+ ions and enable high absolute and relative sensitivities, with maximum values of 0.0172 K−1 and 2.1% K−1 at 523 K, respectively. The results indicated that the as-prepared STO:Mn2+ phosphor can be a potential candidate material for high temperature optical thermometry. [ABSTRACT FROM AUTHOR]

Transition metal ion and/or rare earth ion doped CsPbCl3 nanocrystals (NCs) have attracted extensive attention due to their high combined emission efficiency characteristics. Their high-throughput preparation is of great significance for future industrialization that is still a challenge based on existing batch reaction technologies. Herein, we demonstrate a high-throughput preparation method of Mn2+-doped CsPbCl3 NCs based on a fluidic channel reactor. The as-prepared NCs show vivid yellowish-orange emission at 600 nm and high photoluminescence quantum yield (PLQY) of 63.3%. Meaningfully, due to the closer bond between surface ligands and NCs, NCs prepared by this method show better water durability than NCs obtained using the traditional hot injection method. Finally, a WLED with a high color rendering index (CRI) of 94 and a low correlated color temperature (CCT) of 3626 K was fabricated by combining the as-prepared yellowish-orange Mn-doped CsPbCl3 with the BaMgAl10O17:Eu2+ (BAM:Eu2+) blue phosphor and CaAlSiN3:Eu2+ (CASN:Eu2+) red phosphor on a 375 nm ultraviolet chip. These findings suggest that the Mn-doped CsPbCl3 prepared by the fluidic channel reaction is suitable for WLEDs. Our work paves the way for achieving a continuous, large-scale preparation of perovskite NCs by a fluidic channel reaction for the development of their WLED solid state lighting applications. [ABSTRACT FROM AUTHOR]

Atomically thin two-dimensional (2D) bismuth oxychalcogenides have been considered as promising candidates for high-speed and low-power photoelectronic devices due to their high charge carrier mobility and excellent environmental stability. However, the photoelectric performance of their bulk materials still falls short of expectations. Herein, a novel Bi9O7.5S6/SnS composite film with a type-II heterojunction was successfully prepared by combining hydrothermal and knife-coating techniques. The crystal structure, morphology, and optical properties were systematically investigated. Under 1 V bias voltage, the photocurrent of the Bi9O7.5S6/SnS composite film can be obtained as 107 μA cm−2, which is about 29.9 times and 93.9 times higher than that of bare Bi9O7.5S6 and SnS, respectively. The type-II heterojunction has played a significant role in improving the photoelectric performance of the Bi9O7.5S6/SnS composite film by facilitating the separation and transfer of photo-generated carriers. This work sheds light on the design and development of new bismuth-based composite materials for advanced photoelectric and photocatalytic applications. [ABSTRACT FROM AUTHOR]

Oxygen-deficient TiO2-based composites have attracted widespread attention due to their promoted light-harvesting capacity and energy conversion efficiency, beneficial for water splitting. Despite being a facile, secure-safe and undefiled route for preparing blackened TiO2, the Al-reduction method has not been adopted for preparing TiO2/TiO2−x/CdS composite films. Herein, TiO2/TiO2−x/CdS composite nanorods were successfully fabricated by combining hydrothermal, Al-reduction and chemical bath deposition (CBD) techniques. Enhanced visible-light absorption and photoelectrochemical performances have been achieved using TiO2/TiO2−x/CdS heterojunction nanorods. The photocurrent density of TiO2/TiO2−x/CdS was obtained to be 7.75 mA cm−2 at 0 V vs. Ag/AgCl under AM 1.5 G illumination, which was 77.5-fold and 12.1-fold higher than those of bare TiO2 and CdS, respectively. This work may offer new insights for realizing TiO2-based composites with improved solar absorption for photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

Low-dimensional metal halides have attracted extensive attention because of their superior optoelectronic properties, high stability and structural diversity. In this work, we report a two-dimensional (2D) lead-free halide Cs2MnCl4:Cu+ as a new phosphor for white light-emitting diodes (LEDs). By doping copper(I) into manganese(II) sites, a strong green emission with a photoluminescence quantum yield (PLQY) of 70% was observed. The luminescence center was located at 530 nm and the optimal excitation wavelength was determined to be 310 nm, which suggests a large Stokes shift of 220 nm. Steady-state and transient fluorescence spectra show a decay time of 114.19 μs, indicating a self-trapped exciton (STE) emission mechanism which was further confirmed by temperature-dependent steady-state photoluminescence spectroscopy. This work suggests that manganese halides could be considered as a new family with high luminescence efficiency for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Layered bismuth oxychalcogenides have been demonstrated as potential candidates for high-speed and low-power electronics due to their outstanding environmental stability and high carrier mobility, but the photoelectric performance of bulk species is still far from satisfactory. Herein, a novel Bi9O7.5S6/CdS composite film with a type-II heterojunction has been successfully prepared by combining chemical bath deposition (CBD) and spin-coating technologies. The structure, morphology, optical and photoelectric properties of the samples were investigated systematically. The photoelectric current of the Bi9O7.5S6/CdS composite film was obtained as 32.49 μA cm−2 at 1 V, which is about 13.9-fold and 3.3-fold higher than those of bare Bi9O7.5S6 and CdS. An enhanced photoelectric response and photostability were achieved in the Bi9O7.5S6/CdS composite film, and can be appropriately attributed to the improved separation and transfer of photogenerated carriers driven by the type-II heterojunction. This work offers a promising route to develop high-performance visible-light photoelectric devices with type-II heterojunctions. [ABSTRACT FROM AUTHOR]

A novel quaternary oxysulfide, FeOCuS has been successfully synthesized with a tetragonal anti-PbO-type structure and a visible-light bandgap of about 1.37 eV. Driven by only a 0.4 V bias voltage under simulated AM 1.5 G illumination, a high photocurrent density of 3.89 mA cm−2 has been achieved, revealing the potential optoelectronic applications. [ABSTRACT FROM AUTHOR]

Silver nanowires (AgNWs) have shown great promise as transparent conductive films (TCFs) due to their excellent optoelectronic performance. In order to replace indium tin oxide (ITO), considerable intricate methods have been adopted in combination, thus largely restricting their large-scale applications. Currently, it remains a concern that the research on AgNWs-based TCFs is still required great efforts to balance the high optical transparency and low resistance simultaneously. Here, we deposited AgNWs network onto silica nanospheres (SNSs) antireflection (AR) layer via a facile solution method. The assembled SNSs structure can effectively reduce reflection of the substrate. AgNWs-based composite TCFs achieve optical transmittance of 99.84%, elevating the transmittance by 6.94% with the sheet resistance reaching 49.43 Ω sq−1 declined by 8.66% compared to the pristine AgNWs film. Due to the surface adsorption of nanospheres and the mutual electrophilic effect, the interaction between AgNWs and SNSs is strong, hence exerting the synergetic effect on optoelectronic performance. Furthermore, the results have demonstrated that SNSs AR nanostructure contributes to moderating the interface property of pristine AgNWs film, indicating that it is favorable to ameliorate the impact of increased surface roughness stemming from the interwoven nanowires network structure. The whole solution-processed AgNWs/SNSs composite films in our work bring about great potential engineering for transparent conductors or other optoelectronic devices. [ABSTRACT FROM AUTHOR]

With the aim of improving the photocatalytic activity for water splitting, novel core–shell-structured crystalline-BaTiO3/amorphous-BaTiO3−x/crystalline-CdS composite nanocubes are prepared by a facile two-step synthesis approach. Basic characterization techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy are carried out on the as-prepared composite nanocubes in order to confirm the quality of their crystal structure, morphology and chemical components correspondingly. UV-Vis-NIR measurements of the as-prepared composite nanocubes validate the presence of extended visible-light absorbance due to oxygen-deficient BaTiO3−x. Photoelectrochemical tests are carried out on the as-prepared nanocomposite films that are coated directly on indium tin oxide (ITO) glass substrates. The as-prepared composite nanocubes show a photocurrent density of 100 μA cm−2 without electric field poling, whereas they show about 200 μA cm−2 with an electric field poling of 18.8 kV cm−1. This study suggests that the photoelectrochemical performance is highest in our prepared BaTiO3/BaTiO3−x/CdS composite film compared to the pure BaTiO3, CdS and BaTiO3/BaTiO3−x films, and it may offer a new potential route for designing cost-effective, highly stable and efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Ferroelectric photovoltaics, as a new type of solar cell, relying on an internal electric field instead of p–n or Schottky junctions, can considerably improve the efficiency of charge separation and migration. But, non-volatile elements containing ferroelectrics with narrow bandgaps and excellent photoelectric performances are still scarce. Herein, a new ferroelectric compound, BaFe4O7, has been synthesized by a conventional hydrothermal method. A polar trigonal structure (P31c) was proposed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. UV-vis-NIR diffuse reflectance spectrum revealed a visible-light bandgap Eg of 2.18 eV. Intrinsic ferroelectricity with a high Curie temperature (Tc ∼ 791 K) was confirmed by dielectric and ferroelectric measurements. The electrical saturation polarization (Ps), remanent polarization (Pr) and coercive field (Ec) were determined as 6.34 μC cm−2, 3.32 μC cm−2 and 42.38 kV cm−1 respectively. A bulk photovoltaic effect was observed in the poled sample with a steady-state photocurrent of 39 nA cm−2 and photovoltage of 0.19 V under standard AM 1.5G illumination, which demonstrated its promising applications in photoelectric devices. [ABSTRACT FROM AUTHOR]

The performance of graphene transparent conductive films (TCFs) can be greatly enhanced by introducing an antireflection (AR) nanostructure. We directly deposited graphene on silica nanosphere/acid-catalyzed silica layer (SNS/a-SL) AR nanostructure by assisted catalysis of Cu nanoparticles in ambient pressure chemical vapor deposition to obtain graphene composite TCFs. By introducing the SNS/a-SL AR nanostructure, the transmittance and sheet resistance of graphene TCFs achieved were 89.65% and 2.04 kΩ sq−1, respectively. Compared to graphene films, the transmittance was improved by 5.5% and sheet resistance was reduced by 0.44 kΩ sq−1. The SNS/a-SL AR nanostructure effectively reduced reflection from the substrates owing to the structure of gradient refractive index and exhibited good stability at high temperatures because of the existence of a-SL. The AR nanostructure also could provide more electronic transport channels to achieve regulation of the electrical property of graphene TCFs. This method simultaneously improves the transmittance and conductivity of graphene TCFs by a facile process, providing an important method to prepare graphene TCFs with excellent performance. [ABSTRACT FROM AUTHOR]

Layered bismuth oxychalcogenides have been considered exciting material systems with potential applications in superconductivity and thermoelectricity, but their optoelectronic properties still require greater diligence. The pressure-driven 2D–3D structural reconstruction is an efficient strategy to in situ tune the electronic configuration of functional materials, and yet has remained a challenge for both fundamental studies and technological applications. Here, we present the pressure-driven buckling effects of the layered bismuth oxysulfide Bi9O7.5S6 on a 3D network structure. Although no crystallographic symmetry change was observed up to 58.1 GPa, the layer and bonding distances between and within BiO and BiS layer changed dramatically, which drives the enhancements of electric conductivity by 6 orders of magnitude, increasing the photocurrent by 4 orders of magnitude, and significant narrowing down of band gap from 1.34 eV to 0.45 eV. These findings may open a new avenue for discovering and designing high-efficiency photodetectors and energy-harvesting materials. [ABSTRACT FROM AUTHOR]

Minimization of the lattice thermal conductivity (κL) in thermoelectric (TE) materials is a widely applied strategy to improve the thermoelectric performance of these materials. Dislocations have been demonstrated to be effective in scattering the mid-frequency phonons, which can dramatically reduce the κL in combination with the nanostructures and point defects. Generally, plastic deformation is the most straightforward method to generate dislocations in an alloy. However, most TE materials cannot readily deform plastically due to their brittleness. Herein, we have demonstrated that shock compression is effective in generating high-density dislocations (∼7.9 × 1012 cm−2) in TE materials. Shock compression is an extreme regime of deformation with ultra-high strain rates (＞106 s−1) and high pressures (∼GPa), combined with high temperatures during the process. Using this method, multi-scale hierarchical architectures were fabricated in higher manganese silicides (HMS) with nano-sized grains and high-density dislocations. An ultralow lattice thermal conductivity of 1.5 W m−1 K−1 has been achieved in HMS compounds, and the maximum ZT is increased by 47% to 1.0, which is higher than that of most of the ZT values reported for the HMS compounds. These results demonstrate that dense dislocations not only can lower the κL and improve the ZT of HMS, but can also extend the application of the shock compression method to the design of advanced TE materials. [ABSTRACT FROM AUTHOR]

Layered transition-metal chalcogenides have attracted great interest due to their unique electronic and optical properties. Here, we represent two layered quaternary chalcogenides K2CoCu3S4 and K2CoCu3Se4 prepared by a convenient hydrothermal route. From powder XRD and TEM analyses, K2CoCu3Q4 possesses a tetragonal ThCr2Si2-type structure with a random arrangement of Co and Cu atoms. The phase purity of the samples was confirmed by ICP, SEM, and EDS analyses, and the oxidation states of Co and Cu atoms were determined to be +3 and +1 by XPS spectra. Both samples show a weak ferromagnetic behavior at low temperature induced by spin-canted antiferromagnetic ordering. The temperature dependent resistivity, ρ(T), reveals a metallic nature for stoichiometric K2CoCu3S4. The semiconducting behavior of K2CoCu3Se4 could be explained better by variable range hopping (VRH) rather than adiabatic small polaron hopping (SPH). This new series of layered chalcogenides may offer a promising candidate for potential electronic applications. [ABSTRACT FROM AUTHOR]

Enhanced solar light absorption and photocatalytic and photoelectrochemical properties have been achieved in black BaTiO3 with a unique core/shell structure (crystalline BaTiO3@amorphous BaTiO3−x) using an Al-reduction method. This finding may open a new avenue to tune the inert ferroelectric materials toward excellent photocatalysts for advanced applications. [ABSTRACT FROM AUTHOR]

CuInTe2/graphene composites were fabricated by spark plasma sintering and their thermoelectric properties were investigated. Embedding graphene sheets into CuInTe2 led to decreased thermal conductivity, which can be ascribed to the enhanced phonon scattering by the interface between graphene and the matrix. An improved dimensionless figure of merit (ZT) of 0.40 at 700 K was achieved in a CuInTe2/graphene composite with a mass ratio of 80 : 1. [ABSTRACT FROM AUTHOR]

Atomically thin two-dimensional (2D) bismuth oxychalcogenides have been considered as promising candidates for high-speed and low-power photoelectronic devices due to their high charge carrier mobility and excellent environmental stability. However, the photoelectric performance of their bulk materials still falls short of expectations. Herein, a novel Bi 9 O 7.5 S 6 /SnS composite film with a type-II heterojunction was successfully prepared by combining hydrothermal and knife-coating techniques. The crystal structure, morphology, and optical properties were systematically investigated. Under 1 V bias voltage, the photocurrent of the Bi 9 O 7.5 S 6 /SnS composite film can be obtained as 107 μA cm -2 , which is about 29.9 times and 93.9 times higher than that of bare Bi 9 O 7.5 S 6 and SnS, respectively. The type-II heterojunction has played a significant role in improving the photoelectric performance of the Bi 9 O 7.5 S 6 /SnS composite film by facilitating the separation and transfer of photo-generated carriers. This work sheds light on the design and development of new bismuth-based composite materials for advanced photoelectric and photocatalytic applications.

Layered bismuth oxychalcogenides have been demonstrated as potential candidates for high-speed and low-power electronics due to their outstanding environmental stability and high carrier mobility, but the photoelectric performance of bulk species is still far from satisfactory. Herein, a novel Bi 9 O 7.5 S 6 /CdS composite film with a type-II heterojunction has been successfully prepared by combining chemical bath deposition (CBD) and spin-coating technologies. The structure, morphology, optical and photoelectric properties of the samples were investigated systematically. The photoelectric current of the Bi 9 O 7.5 S 6 /CdS composite film was obtained as 32.49 μA cm -2 at 1 V, which is about 13.9-fold and 3.3-fold higher than those of bare Bi 9 O 7.5 S 6 and CdS. An enhanced photoelectric response and photostability were achieved in the Bi 9 O 7.5 S 6 /CdS composite film, and can be appropriately attributed to the improved separation and transfer of photogenerated carriers driven by the type-II heterojunction. This work offers a promising route to develop high-performance visible-light photoelectric devices with type-II heterojunctions.

With the aim of improving the photocatalytic activity for water splitting, novel core-shell-structured crystalline-BaTiO 3 /amorphous-BaTiO 3-x /crystalline-CdS composite nanocubes are prepared by a facile two-step synthesis approach. Basic characterization techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy are carried out on the as-prepared composite nanocubes in order to confirm the quality of their crystal structure, morphology and chemical components correspondingly. UV-Vis-NIR measurements of the as-prepared composite nanocubes validate the presence of extended visible-light absorbance due to oxygen-deficient BaTiO 3-x . Photoelectrochemical tests are carried out on the as-prepared nanocomposite films that are coated directly on indium tin oxide (ITO) glass substrates. The as-prepared composite nanocubes show a photocurrent density of 100 μA cm -2 without electric field poling, whereas they show about 200 μA cm -2 with an electric field poling of 18.8 kV cm -1 . This study suggests that the photoelectrochemical performance is highest in our prepared BaTiO 3 /BaTiO 3-x /CdS composite film compared to the pure BaTiO 3 , CdS and BaTiO 3 /BaTiO 3-x films, and it may offer a new potential route for designing cost-effective, highly stable and efficient photocatalysts.

Layered transition-metal chalcogenides have attracted great interest due to their unique electronic and optical properties. Here, we represent two layered quaternary chalcogenides K2CoCu3S4 and K2CoCu3Se4 prepared by a convenient hydrothermal route. From powder XRD and TEM analyses, K2CoCu3Q4 possesses a tetragonal ThCr2Si2-type structure with a random arrangement of Co and Cu atoms. The phase purity of the samples was confirmed by ICP, SEM, and EDS analyses, and the oxidation states of Co and Cu atoms were determined to be +3 and +1 by XPS spectra. Both samples show a weak ferromagnetic behavior at low temperature induced by spin-canted antiferromagnetic ordering. The temperature dependent resistivity, ρ(T), reveals a metallic nature for stoichiometric K2CoCu3S4. The semiconducting behavior of K2CoCu3Se4 could be explained better by variable range hopping (VRH) rather than adiabatic small polaron hopping (SPH). This new series of layered chalcogenides may offer a promising candidate for potential electronic applications.

Enhanced solar light absorption and photocatalytic and photoelectrochemical properties have been achieved in black BaTiO 3 with a unique core/shell structure (crystalline BaTiO 3 @amorphous BaTiO 3-x ) using an Al-reduction method. This finding may open a new avenue to tune the inert ferroelectric materials toward excellent photocatalysts for advanced applications.