Search

Incorporating substitutional elements from groups I, II and IV is an important approach to improve the quality of kesterite thin films. Among the elements, Ag and Ge are most effective in promoting the performance of Cu2ZnSn(S,Se)4 solar cells. Although several theoretical and experimental studies have been conducted on the Ag/Ge-alloyed kesterite, there are significant differences in the reported morphological characteristics, photovoltaic performance and even the optimal Ag/Ge substitution ratio due to different preparation processes utilized, which leads to difficulties in comparing the Ag-incorporated and Ge-incorporated kesterite solar cells. Currently, there is little literature on the comparative study concerned. Herein, we fabricated Ag-alloyed and Ge-alloyed kesterite solar cells based on the same solution method and process conditions, and laterally compared the effects of Ag substitution and Ge substitution on the phase compositions, morphologies, optical bandgaps, minority carrier lifetime and device performance of kesterite Cu2ZnSn(S,Se)4 thin films. [ABSTRACT FROM AUTHOR]

Quasi-zero-dimensional quantum dots (QDs) have garnered significant attention owing to their distinct structural attributes, quantum confinement behaviors, optoelectronic characteristics, etc. Regrettably, their susceptibility to stability poses a challenge. In this context, leveraging rational component regulation and crystallization process optimization strategies, we presented the successful preparation of CdS QDs silicate glass through the amalgamation of melt-quenching and controlled crystallization. The optical and morphological analysis substantiated the accomplishment of in-situ precipitation of CdS QDs within the glass matrix, with grain sizes <20 nm. Integrating CdS QDs into an inorganic glass matrix remarkably augmented its fluorescence thermal stability, enabling the preservation of 85.1 % of the room-temperature luminescent intensity even at an elevated temperature of 150 °C. Moreover, the encapsulated W-LED device by near-UV LED chip, CdS QDs glass, and BaMgAl 10 O 17 :Eu2+ phosphor exhibited a warm white-light emission characterized by suitable chromaticity coordinates (0.3741, 0.3452) and a notably high color rendering index (CRI = 93). Ultimately, the radioluminescence behavior of CdS QDs glass was unveiled by utilizing it as the scintillator wafer in an X-ray imaging system, which clearly demonstrated the structure of spring encapsulated within an opaque capsule. In a nutshell, these demonstrations unequivocally emphasize the substantial potential merits of CdS QDs glass, particularly in the domains of long-term W-LED lighting and X-ray imaging applications. [ABSTRACT FROM AUTHOR]

Rare earth activated color converted phosphors have been widely used in solid-state lighting and display fields. Developing phosphors with high luminous efficiency is of great significance for light-emitting devices. Concentration quenching is the main factor limiting the improvement of phosphor luminescence efficiency during increasing the activator doping level. In this study, a novel structural optimization strategy is developed to overcome the impact of concentration quenching. In Tb3+ activated NaYSiO 4 (NYSO), large-size Gd3+ ions are introduced to adjust the distance of rare earth ions and suppress the energy transfer between Tb3+ luminescent centers. It is shown that at a critical Tb3+ concentration, for which concentration quenching tends to occur in NaYSiO 4 :Tb3+, Gd3+ incorporation successfully raises the internal quantum efficiency from 64.8 % for Tb3+-singly-doped NYSO up to 80.6 % for Gd3+/Tb3+ co-doped one. The findings can offer a feasible pathway in promoting the luminescent properties of silicate phosphor hosts. [ABSTRACT FROM AUTHOR]

Abstract Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) shows great promise in thin film photovoltaic application due to its reasonable band gap, low cost and non-toxic earth-abundant composition. Post-selenization is the generally adopted approach to obtain CZTSSe film with large-grain size. Thoroughly understanding and well controlling the grain growth process during selenization is thus essential for achieving high-performance solar cell devices. Here we demonstrate that the absorber microstructure can be adjusted by altering selenization conditions, especially the heating rate and annealing time. It is found that heating rate determines formation manner of top CZTSSe layer, while annealing time affects both the crystallization degree of bottom CZTSSe layer and the selenization of Mo contact layer. Properly adjusting the annealing time at an optimized heating rate is proven to successfully eliminate the fine-grain layer and obtain high quality CZTSSe thin films with large-size grains. Based on the observations, growth mechanisms for the microstructure development during selenization of solution processed Cu 2 ZnSnS 4 films are suggested. Finally, CZTSSe device efficiency of 9.24% is achieved at an optimal selenization condition. Highlights • The growth mechanisms of the solution processed Cu 2 ZnSn(S,Se) 4 thin films are suggested. • The bottom fine-grain layer and the thickness of MoSe 2 can successfully adjust by changing the selenization conditions. • The PCE of CZTSSe solar cells is significantly enhanced from 7.06% to 9.24% by optimizing the selenization conditions. [ABSTRACT FROM AUTHOR]

Dimethyl sulfoxide (DMSO) based solution has been proven promising in preparing high-quality Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorbers. In the present work, H 2 O is used as a simple and effective additive to optimize the film formation of DMSO based CZTS precursor. It is demonstrated that a small amount of H 2 O introduction into the DMSO solution reduced the oxygen content in the CZTS precursor film, and thus limited the formation of SeO 2 /Sn(O,Se) x secondary phase in the final CZTSSe layer. As a result of improved morphology and carrier collection ability of absorber layer, the power conversion efficiency (PCE) is enhanced significantly from 7.45% for CZTSSe solar cell device prepared with pure DMSO precursor solution to 9.30% for that with an optimized DMSO/H 2 O ratio. Applying the same preparing strategy to the Ag containing CZTSSe device, we finally achieved a PCE of 10.3% under 1-sun illumination. [ABSTRACT FROM AUTHOR]

Highly active and durable hydrogen evolution reaction (HER) catalysts are required for the low-cost and high-yield generation of clean energy from water splitting. Herein, a Cu3BiS3/TiO2 (C@T) heterojunction film is constructed by a facile dip-coating method for the synthesis of Cu3BiS3 nanorods on a TiO2 film. The heterojunction film is used as a catalyst in water splitting which exhibits a higher photoelectrochemical (PEC) performance and electrocatalytic activity than the respective pure Cu3BiS3 nanorods counterpart. Experimental results confirm that the PEC performance of the C@T heterojunction film displays a strong photoresponse of as high as ∼1.5 × 10−4 A cm−2 at an applied potential of −0.5 V vs. Ag/AgCl under visible light irradiation. What's more, the as-prepared C@T film shows the best electrocatalytic performance with an onset overpotential of 150 mV, a low Tafel slope of 42.67 mV dec−1, a large current density of 10.8 mA cm−2 at an overpotential of 220 mV, and a remarkable cycling stability. The enhanced PEC performance is associated with the formation of a heterojunction structure at the interface between TiO2 and Cu3BiS3, which facilitates light absorption and separation of photogenerated charge carriers. The growth of Cu3BiS3 nanorods on a TiO2 film modified the electronic structure and increased the electrochemical area, and thus is responsible for enhanced catalytic activity. Benefitting from its scalable preparation and properties, the Cu3BiS3 nanorods/TiO2 heterojunction film is indeed a promising catalyst for hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Nano-sized materials have attracted tremendous attentions because of their promising practical applications and theoretical values. The nano-sized materials are able to not only enhance the intrinsic properties of their bulk counterparts but also give birth to new promising properties. Herein, heterojunctions consisted of graphene oxide (GO) and three different MoS nanostructures, including nanoflowers, nanoparticles, and quantum dots, were constructed and used as photocatalysts in water splitting. The electrochemical behavior and photocatalytic performance of MoS/GO composites were found closely related to the particle size and morphology of MoS. Compared to bulk MoS/GO photocatalyst, nano-sized MoS/GO heterostructures exhibited obviously enhanced performance in photocatalytic hydrogen generation. Benefitting from the surface effect and the quantum confinement in MoS quantum dots, MoS quantum dots/GO displayed the highest photocatalytic activities. This study indicates that the decrease in the dimension of MoS can effectively increase the photocatalytic hydrogen evolution performance of MoS/GO heterostructures, and thus suggests preferred strategy to design other HER photocatalysts based on MoS. [ABSTRACT FROM AUTHOR]

A large–grain and highly crystalline Cu 3 BiS 3 thin film is successfully prepared by a dimethyl sulfoxide (DMSO)–based solution coating process. Without involving post sulfurization, Cu 3 BiS 3 absorber with grain size of ~ 1 µm has been achieved via a short-time drying of spin–coated precursor film on a hot plate at relatively low temperatures (< 300 °C). Our Cu 3 BiS 3 film exhibits a direct band gap of 1.47 eV with high absorption coefficients (~ 7 × 10 4 cm −1 ). Hall effect measurements reveal a p–type conductivity with hole concentration of ~ 10 16 cm −3 and mobility of 52.83 cm 2 /(V s). Moreover, an initial Cu 3 BiS 3 thin film solar cell with the device structure of glass/Mo/Cu 3 BiS 3 /CdS/ZnO/ITO/Al is fabricated, achieving a definite conversion efficiency of 0.17%. The mild preparation condition promises great potential of current method in realizing Cu 3 BiS 3 solar cells on temperature-sensitive substrates such as flexible polymer through an energy efficient way. The Cu 3 BiS 3 has thus been presented as a promising absorber material for solar cell applications. [ABSTRACT FROM AUTHOR]

The frequency dependent capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of Schottky barrier diodes (SBDs) with Cu contacts on Si doped GaAsN epilayers with (100) and (311)A/B orientations have been investigated in the frequency range from 20 kHz to 1 MHz at room temperature. C, G/ω and the deduced series resistance (R s ) show strong dependences on the applied frequency in the forward bias region, which is closely correlated to the frequency-dependent response of interface states (N ss ). In GaAsN SBDs with all three growth orientations, the increasing N composition is found to increase the peak value of capacitance and enhance its dependence on frequency, which thus implies a general rule that increasing N incorporation causes an increase in N ss . The increasing extent of N ss due to N incorporation, however, differs a lot for different growth orientations as analyzed by using Hill-Coleman method. It is revealed that (311)B is the promising growth orientation to suppress the N ss generation over a wider N composition range in GaAsN Schottky devices. The reduced formation probability of non-substitutional N due to the efficient N incorporation on the (311)B plane is considered to be responsible for the observations. [ABSTRACT FROM AUTHOR]

Using first-principles total energy calculations, we have studied the structural, mechanical and electronic properties of GaAs 1- x N x ternary semiconductor alloys with the zinc-blende crystal structure over the whole nitrogen concentration range (with x from 0 to 1) within density functional theory (DFT) framework. To obtain the ideal band gap, we employ the semi-empirical approach called local density approximation plus the multi-orbital mean-field Hubbard model (LDA+U). The calculated results illustrate the varying lattice constants and band gap in GaAs 1- x N x alloys as functions of the nitrogen concentration x . According to the pressure dependence of the lattice constants and volume, the higher N concentration alloy exhibits the better anti-compressibility. In addition, an increasing band gap is predicted under 20 GPa pressure for GaAs 1- x N x alloys. [ABSTRACT FROM AUTHOR]

The structural, electronic and optical properties of Cu3SbS4 with different crystalline structures have been investigated by using the PBE generalised gradient approximation and hybrid functional method (HSE06) to density functional theory at ambient and high pressure. The calculated elastic constants and phonon dispersions reveal that both the famatinite and enargite phases are mechanically and dynamically stable, except for the cubic [ABSTRACT FROM AUTHOR]

The growth orientation dependence of N incorporation on traditional (100) and high-index GaAs (311)A/B planes has been investigated by the first principle calculation and experimental measurement. Due to the electronegativity and atomic radius differences between As and N atoms, the Ga N bond is much shorter than the corresponding Ga As bond as N occupies As atom site. The optimization to energetically preferred construction leads to the inward moving of N atom, while the displacement extent of three surface models exhibits considerable differences. More importantly, the theoretical result reveals a lower formation energy of N doping for N@(311)B GaAs surface and a larger one for N@(311)A GaAs surface as compared with the traditional (100) GaAs plane. The first principle investigations thus suggest the enhanced N incorporation in (311)B GaAsN, which is in good accordance with the secondary ion mass spectrometry (SIMS) measurement results of GaAsN layers by chemical beam epitaxy (CBE). [ABSTRACT FROM AUTHOR]

The contact behavior of Cu on n-type GaAsN, grown on (100) and (311)A/B GaAs substrates by chemical beam epitaxy, has been investigated by current–voltage (I–V) and capacitance–voltage (C–V) measurements. Both N incorporation and growth orientation are found to influence the electrical properties of Cu/GaAsN Schottky diodes. The increasing N composition leads to an increase in the ideality factor and Schottky barrier height (C–V), whereas a decrease in the carrier concentration in samples with all adopted growth orientations. Compared with (100) and (311)B samples, the Schottky diodes constructed on (311)A GaAsN epilayer exhibit better performance with ideality factor close to 1 and higher barrier height. The interfacial chemical reaction between metal layer and surface atoms on the growth surface is believed to account for the observations. [ABSTRACT FROM AUTHOR]

Cu 2 ZnSn(S x Se 1−x ) 4 (CZTSSe) nanocrystals (NCs) are synthesized via a one-pot solvothermal method under the mild reaction condition. By varying the S/Se ratio in the solution, the chalcogen composition of CZTSSe NCs can be well controlled over the whole range, leading to a tunable bandgap from 1.11 to 1.49 eV. Furthermore, it reveals that the S/Se ratio of anionic precursors has a dramatic effect on the phase structure of CZTSSe NCs. When the S/(S + Se) ratio (x) is higher than 0.5, wurtzite (WZ)-derived structure is the dominant phase; on the contrary, the zinc blende (ZB)-derived structure overwhelms the former as x gradually reduces from 0.5 to 0. Our findings thus suggest a novel and facile method to obtain CZTSSe NCs with metastable WZ phase, which is distinguished from previously reported routes based on carefully choosing organic solvents and/or capping ligands. In addition, the obtained CZTSSe NCs are readily dispersed in low boiling point and low toxicity solvent to form homogeneous and stable NCs ink. The photocurrent response measurement on the CZTSSe NCs films demonstrates its potential as a low-cost, high-reproducibility and high-yield NC preparing approach towards efficient CZTSSe solar cells. [ABSTRACT FROM AUTHOR]

Rare earth silicate phosphors of high quantum efficiency with a stable performance are promising materials in the fields of display and illumination. The grain sizes of products synthesized via the conventional solid-state reaction method are usually too large to satisfy the requirements of color cast and extraction efficiency in high-resolution light-emitting devices (LEDs). We designed a synthetic route and successfully fabricated rare earth silicate NaGd9Si6O26 (NGSO) sub-microcrystals with a size ranging from 550 to 1200 nm. The reaction mechanism and optical properties were systematically investigated. The quantum efficiency of Eu3+-activated NGSO sub-microcrystals was about 36.6%. The LED encapsulated with these sub-microcrystals showed lower color deviation and higher lumen efficiency and lumen flux compared to that with NGSO fabricated using the conventional solid state reaction method. [ABSTRACT FROM AUTHOR]

Cs2SnCl6 double perovskite has attracted wide attention as a promising optoelectronic material because of its better stability and lower toxicity than its lead counterparts. However, pure Cs2SnCl6 demonstrates quite poor optical properties, which usually calls for active element doping to realize efficient luminescence. Herein, a facile co-precipitation method was used to synthesize Te4+ and Er3+-co-doped Cs2SnCl6 microcrystals. The prepared microcrystals were polyhedral, with a size distribution around 1–3 μm. Highly efficient NIR emissions at 1540 nm and 1562 nm due to Er3+ were achieved in doped Cs2SnCl6 compounds for the first time. Moreover, the visible luminescence lifetimes of Te4+/Er3+-co-doped Cs2SnCl6 decreased with the increase in the Er3+ concentration due to the increasing energy transfer efficiency. The strong and multi-wavelength NIR luminescence of Te4+/Er3+-co-doped Cs2SnCl6 originates from the 4f→4f transition of Er3+, which was sensitized by the spin-orbital allowed 1S0→3P1 transition of Te4+ through a self-trapped exciton (STE) state. The findings suggest that ns2-metal and lanthanide ion co-doping is a promising method to extend the emission range of Cs2SnCl6 materials to the NIR region. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have great potential for future application. However, the commercialization of PSCs is limited by the prohibitively expensive and doped hole-transport materials (HTMs). In this regard, small molecular dopant-free HTMs are promising alternatives because of their low cost and high efficiency. However, these HTMs still have a lot of space for making further progress in both efficiency and stability. This review firstly provides outlining analyses about the important roles of molecular orientation when further enhancements in device efficiency and stability are concerned. Then, currently studied strategies to control molecular orientation in small molecular HTMs are presented. Finally, we propose an outlook aiming to obtain optimized molecular orientation in a cost-effective way. [ABSTRACT FROM AUTHOR]

La2Ti2O7 has been perceived as a potential photocatalytic material candidate for hydrogen evolution in recent years. However, its wide band gap brings about a narrow light absorption range and thereby results in poor photocatalytic activity. Herein, to enhance the light absorption capability, as well as promote the separation of photogenerated carriers, a CuInS2/La2Ti2O7 heterojunction photocatalyst was designed. A narrow band-gap semiconductor, CuInS2, was grown in situ on the surface of La2Ti2O7 by a solvothermal method. The effects and related mechanisms of CuInS2 loading on the photocatalytic activity were systematically investigated. The composite photocatalysts present a much better hydrogen evolution performance than the single materials. The highest hydrogen evolution rate reaches 64.41 μmol g−1 h−1. The enhancement of hydrogen evolution performance can be ascribed to the improvement of light absorption, as well as the acceleration of separation of photogenerated carriers, due to the loading of CuInS2 and the formation of a type II heterojunction between two materials. [ABSTRACT FROM AUTHOR]

The replication of nano-patterns is a significant means of nanomanufacturing. However, there is still a dearth of nano-replication methods that meet the requirements of both high precision and low cost. Therefore, a new strategy to achieve the replication of nano-patterns, namely centrifugal-force-driven nano-replication (CFDNR), is proposed here. An easily obtained centrifugal force which is perpendicular to the plane of a nanostructured template is designed as a driving power, to compel the dynamic polymer to fully fill the space of the template; then, the nano-pattern can be replicated on a polymer film. Anodic aluminum oxide (AAO) templates with nanohole periods of ~450 nm and ~100 nm were employed as the original masters to investigate the nano-replication behaviors. The results of morphology measurements demonstrate excellent precision. The size deviations between the nanohole in the template and the nanopillar on the polymer film are less than 4%. Furthermore, a vacuum-assisted CFDNR scheme is proposed to prevent the formation of cavitation on the polymer replica. This work provides new possibilities and choices for facile, inexpensive and high-precision nanomanufacturing. [ABSTRACT FROM AUTHOR]

Abstract: A facile and low-cost approach was developed to prepare high quality quaternary Cu2ZnSnS4(CZTS) alloys through the thermal treating of the core–shell Cu2SnS3@ZnS nanoparticles. The synthesis process of the core–shell structure involves a simple two-step hydrothermal route that starts from the well-dispersed ternary Cu2SnS3 core with the introduction of poly(vinylpyrrolidone) (PVP) in the reaction solution, and ended by the coated binary ZnS shell upon the adsorption of citrate groups onto the preformed cores. X-ray diffraction, Raman spectrum and UV–vis absorption spectrum confirmed the single-phase formation and the proper bandgap of 1.51eV for the CZTS alloys. This effective hydrothermal method can be readily applied for industrial production. [Copyright &y& Elsevier]

To explore the origin of low conversion efficiency of GaAsN solar cells, the effects from a key deep level (E1) at about 0.3-0.4 eV below the conduction band and interface states between the GaAsN emitter and GaAs front surface field layer were investigated by numerical simulation. Our results show that a high deep level concentration in GaAsN layers and a large interface recombination velocity are necessary to fit the experimental data. Interface recombination plays an important role in reducing the quantum efficiency in the short-wavelength region. Its effect can be weakened by applying a thin emitter and a high doping level in the GaAs surface field layer. The abundant existence of E1 is responsible for the high contribution of Shockley-Read-Hall recombination from the space-charged region. Its density should be reduced to <1015 cm-3 for higher conversion efficiency. [ABSTRACT FROM AUTHOR]

We report photoluminescence (PL) studies of both as-grown and electron-irradiated GaAsN epilayers on (311)A/B and (100) GaAs substrates. A long room-temperature (RT) PL lifetime, as well as an enhanced N incorporation, is observed in (311)B GaAsN epilayers as compared with (311)A and (100) samples. There is no direct correlation between the RT PL lifetime and the emission intensity from Ga vacancy complex detected at low temperature. The lifetime damage coefficient is relatively low for (311)B GaAsN. The irradiation-induced nonradiative recombination defects are suggested to be N- and/or As-related according to a geometrical analysis based on the tetrahedral coordination of GaAsN crystal. [ABSTRACT FROM AUTHOR]

Abstract: The effects of In doped low-temperature (LT) AlGaN interlayer on the properties of GaN/Si(111) by MOCVD have been investigated. Using In doping LT-interlayer can decrease the stress sufficiently for avoiding crack formation in a thick (2.0μm) GaN layer. Significant improvement in the crystal and optical properties of GaN layer is also achieved. In doping is observed to reduce the stress in AlGaN interlayer measured by high-resolution X-ray diffraction (HRXRD). It can provide more compressive stress to counteract tensile stress and reduce crack density in subsequent GaN layer. Moreover, as a surfactant, indium is observed to cause an enhanced PL intensity and the narrowed linewidths of PL and XRD spectra for the LT-interlayer. Additionally, the crystal quality of GaN layer is found to be dependent on the growth parameters of underneath In-doped LT-AlGaN interlayer. The optimal parameters, such as TMIn flow rate, TMAl flow rates and thickness, are achieved to obtain nearly 2.0μm thick crack free GaN film with advanced optical and crystal properties. [Copyright &y& Elsevier]

Abstract: The subband structure and inter-subband transition as a function of gate voltage are determined by solving the Schrödinger and Poisson equations self-consistently in an Al x Ga1− x N/GaN heterostructure. Different aluminum mole fraction and thickness of Al x Ga1− x N barrier are considered. Calculation results show that energy difference between the first and second subband covers a wide range (from several tens to hundreds milli-electron volt) by applying different gate voltage, which corresponds to the midinfrared and long-wave infrared wavelength scope. Furthermore, such a modulation on the subband transition energy is much more pronounced for the structure with thin barrier. When the applied positive gate voltage is increased, the triangle well formed at the interface turns to be deeper and narrower, which enhances the confinement for electrons. As a result, the overlap between electron wave function at two subbands increases, and thus the optical intersubband transition also enhances its intensity. This tendency is in good agreement with the available data in the literature. [Copyright &y& Elsevier]

Abstract: A new method is demonstrated to be effective in reducing mismatch-induced tensile stress and suppressing the formation of cracks by inserting InAlGaN interlayers during the growth of GaN upon Si(111) substrate. Compared with GaN film without quaternary interlayer, GaN layer grown on InAlGaN compliant layers shows a five times brighter integrated PL intensity and a (0002) High-resolution X-ray diffraction (HRXRD) curve width of 18arcmin. Its , derived from Rutherford backscattering spectrometry (RBS), is about 2.0%, which means that the crystalline quality of this layer is very good. Quaternary InAlGaN layers, which are used as buffer layers firstly, can play a compliant role to endure the large mismatch-induced stress and reduce cracks during the growth of GaN epitaxy. The mechanisms leading to crack density reduction are investigated and results show that the phase immiscibility and the weak In–N bond make interlayer to offer tenability in the lattice parameters and release the thermal stress. [Copyright &y& Elsevier]

Abstract: InGaN/GaN quantum dots were grown on the sapphire (0001) substrate in a metalorganic chemical vapor deposition system. The morphologies of QDs deposited on different modified underlayer (GaN) surfaces, including naturally as grown, Ga-mediated, In-mediated, and air-passivated ones, were investigated by atomic force microscopy (AFM). Photoluminescence (PL) method is used to evaluate optical properties. It is shown that InGaN QDs can form directly on the natural GaN layer. However, both the size and distribution show obvious inhomogeneities. Such a heavy fluctuation in size leads to double peaks for QDs with short growth time, and broad peaks for QDs with long growth time in their low-temperature PL spectra. QDs grown on the Ga-mediated GaN underlayer tends to coalesce. Distinct transform takes place from 3D to 2D growth on the In-mediated ones, and thus the formation of QDs is prohibited. Those results clarify Ga and In''s surfactant behavior. When the GaN underlayer is passivated in the air, and together with an additional low-temperature-grown seeding layer, however, the island growth mode is enhanced. Subsequently, grown InGaN QDs are characterized by a relatively high density and an improved Gaussian-like distribution in size. Short surface diffusion length at low growth temperature accounts for that result. It is concluded that reduced temperature favors QD''s 3D growth and surface passivation can provide another promising way to obtain high-density QDs that especially suits MOCVD system. [Copyright &y& Elsevier]

Multilayer InGaN/GaN quantum dots (QDs) were grown on sapphire substrates through a three-dimensional growth mode, which was initiated by a special passivation processing introduced into the normal growth procedure. Surface morphology and photoluminescence properties of QDs with different stacking periods (from one to four) were investigated. The temperature dependences of the PL peak energies were found to show a great difference between two-layer and three-layer QDs. The fast redshift and the reversed sigmoidal temperature dependences of the PL energies for the former were attributed to the thermally activated carrier transfer from small to large dots. However, the increase of both the dot size and the spatial space among dots with the growing stacking periods reduced the carrier escape and retrapping. [Copyright &y& Elsevier]

Amorphous carbon (a-C) films were deposited on a single-crystal silicon substrate by direct current magnetron sputtering system. The effect of Cr+ ion-implantation on the structure and tribological properties of the sputtered a-C films were investigated by means of Raman spectrometric analysis, X-ray photoelectron spectroscopic analysis, and friction and wear measurements. The morphology of the worn film surfaces was observed with a scanning electron microscope (SEM). The structure of a-C tended to be disordered and had a growth of sp3 content at high implantation doses. The sputtering depth profiles of the films by X-ray photoelectron spectroscopy indicate that chromium carbide is formed at the film–substrate interface where the implanted Cr+ has a higher concentration. The interface between Si and C is widened by ion-implantation. Thus the anti-wear behavior of the ion-implanted film is improved. The brittleness of the a-C film is increased after implantation with Cr+ at a larger dose. This is attributed to the generation of chromium carbide from the reaction of carbon and Cr. Subsequently the film implanted with Cr+ at a relatively low dose is characterized by adhesive wear, while that implanted at a higher dose characterized by abrasive wear. [Copyright &y& Elsevier]

Layered perovskite-type semiconductor La2Ti2O7 has attracted lots of attention in photocatalytic hydrogen evolution, due to the suitable energy band position for water splitting, high specific surface area, and excellent physicochemical stability. However, the narrow light absorption range and the low separation efficiency of photogenerated carriers limit its photocatalytic activity. Herein, plate-like La2Ti2O7 with uniform crystal morphology was synthesized in molten NaCl salt. A p-n heterojunction was then constructed through the in situ hydrothermal growth of p-type Co3O4 nanoparticles on the surface of n-type plate-like La2Ti2O7. The effects of Co3O4 loading on photocatalytic hydrogen evolution performance were investigated in detail. The results demonstrate that composite Co3O4/La2Ti2O7 possesses much better photocatalytic activity than the pure component. The composite photocatalyst with 1 wt% Co3O4 exhibits the highest hydrogen evolution rate of 79.73 μmol·g−1·h−1 and a good cycling stability. The photoelectrochemistry characterizations illustrate that the improvement of photocatalytic activity is mainly attributed to both the enhanced light absorption from the Co3O4 ornament and the rapid separation of photogenerated electron-hole pairs driven by the built-in electric field close to the p-n heterojunction. The results may provide further insights into the design of high-efficiency La2Ti2O7-based heterojunctions for photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Oxyfluoride glass-ceramics have become a focal point of recent research, positioned to advance significantly in areas such as LED illumination and optical data storage, etc. This study successfully prepared Pr3+-doped fluorosilicate glass and glass-ceramics embedded Na 5 Y 9 F 32 nanocrystals. The introduction of Pr 2 O 3 into the glass matrix disturbs the network structure, leading to a reduction in the band gap from 3.66 eV to 3.42 eV. When subjected to 443 nm light excitation, the 1.0 mol% Pr3+-doped glass-ceramics crystallized at 690 °C for 1.0 h exhibit the most potent luminescence, displaying seven emission peaks resulting from the radiative transition of Pr3+ ions, manifesting yellowish-pink hues. Furthermore, when stimulated by a 450 nm LD, the glass-ceramics display a distinct emission peak at approximately ∼247 nm, attributed to the electron transitions of 4 f 5 d → 3H 4 for Pr3+ ions. The luminescent properties of these glass-ceramics embedded with Na 5 Y 9 F 32 nanocrystals illustrate potential applications in up-conversion and down-conversion luminescence. • A novel Pr3+ doped SiO 2 –Al 2 O 3 –Na 2 O-NaF-YF 3 glass-ceramics was successfully prepared. • Glass-ceramics containing Na 5 Y 9 F 32 crystals exhibit efficient excitation under blue light. • The glass-ceramics exhibit yellowish-pink hues excited by 443 nm light. • The glass-ceramics presents impressive emission peaks at ∼247 nm excited by 450 nm LD. • The work stresses glass-ceramics' huge potential in up-/down-conversion luminescence. [ABSTRACT FROM AUTHOR]

Luminescent glass-ceramics has garnered significant attention within the research community owing to its exceptional characteristics, including robust chemical stability, outstanding thermal stability, and efficient thermal conductivity. However, persistent challenges include issues related to suboptimal luminous efficiency and color rendering index. In the context of this research endeavor, we have achieved a noteworthy achievement by successfully fabricating a novel variant of glass-ceramics doped with both Eu2+ and Eu3+ ions within the Na 2 O-CaO-SiO 2 system glass. This innovative glass-ceramics composition encompassed Na 4 Ca 4 Si 6 O 18 crystals, characterized by grain sizes <110 nm. Our investigations, featuring comprehensive optical spectra analysis and detailed morphological examinations, have provided substantial evidence indicating the preferential occupation of Eu3+ ions in the Ca2+ sites residing within the Na 4 Ca 4 Si 6 O 18 crystal lattice, conversely, it is possible that the distribution of Eu2+ ions occurred within the glass matrix. Additionally, it is worth noting that this glass-ceramic material demonstrated a heightened excitation efficiency when subjected to 464 nm blue light, surpassing its performance with 393 nm violet light. Detailed fluorescence spectral analysis unveiled the impressive internal quantum efficiency of the glass-ceramics, reaching an impressive 80.27%, and this glass-ceramics exhibited remarkable fluorescence thermal stability at 150 °C, preserving approximately ∼75% of its luminescent intensity at room temperature. Furthermore, we have encapsulated the white light-emitting diode (W-LED) device, integrated with a 460 nm LED chip, optimized glass-ceramics, and YAG: Ce3+ phosphor. The outcomes were characterized by the warm white-light emission, suitable chromaticity coordinates, a high color rendering index (approximately 85.4), and impressive luminous efficiency (up to 112.47 lm/W). In summary, these findings unequivocally underscore the substantial potential of glass-ceramics in the realm of high-power W-LED lighting applications. • A novel Eu3+/Eu2+ co-doped Na 2 O-CaO-SiO 2 glass-ceramics was successfully prepared. • Glass-ceramics containing Na 4 Ca 4 Si 6 O 18 crystals exhibit efficient excitation under blue light. • The glass-ceramics presents impressive IQE (80.27%) and excellent thermal stability. • The encapsulated W-LED device exhibits high CRI, and impressive luminous efficiency. • The work emphasizes the huge potential of glass-ceramics in high-power W-LED lighting. [ABSTRACT FROM AUTHOR]

The design of highly efficient and stable photoelectrocatalysts for the hydrogen evolution reaction (HER) is critical to the large-scale application of clean hydrogen energy. Here, Cu3BiS3 nanoflowers (NFs) with photoelectrochemical (PEC) activity were synthesized via a solvothermal method under mild and low-toxic reaction conditions, and the Au nanoparticles (Au NPs) were loaded onto Cu3BiS3 NFs to improve the photoelectrocatalytic performance. Compared with pure Cu3BiS3 NFs, Au-Cu3BiS3 composites (A@C) exhibit a much higher photocurrent density (2 × 10−4 A cm−2) and greatly enhanced photoelectrocatalytic activity (2.31 μmol h−1), which are attributed to the enhancement in electron capture abilities, active sites and visible light absorption from the localized surface plasmon resonance effect (LSPR) of Au NPs. Furthermore, the excellent conductivity of Au NPs can effectively accelerate the separation and collection of photogenerated carriers. This work highlights a feasible strategy to improve the PEC activity of the Cu3BiS3 photoelectrocatalyst, and confirms the great potential of Au-Cu3BiS3 composites for hydrogen evolution applications. [ABSTRACT FROM AUTHOR]

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) have proven to be promising materials for photovoltaic applications. The current state-of-the-art CZTSSe photovoltaic device improvements in efficiency have been hampered by difficulties in increasing open circuit voltages (VOC). Herein, we thoroughly analyzed the proton irradiation hardness and its loss mechanism of CZTSSe thin film solar cells. The efficiency loss mechanism of the CZTSSe solar cell is proposed by systematically studying the device performance, optical and electrical properties, and distribution changes in elements upon proton irradiation. It was revealed that proton-irradiation-induced element diffusion in device affects the absorber properties and CdS/CZTSSe heterojunction dramatically and deteriorates the performance of the device. Finally, the main factors that may affect device performance of CZTSSe solar cells are highlighted, and the CZTSSe solar cells also demonstrate a remarkable radiation hardness. [ABSTRACT FROM AUTHOR]

To quantitatively evaluate the formation energies of the (N-N)As/(N-As)As/(As-As)As split interstitials in dilute GaAsN alloys, first-principles total-energy calculations using a projector augmented wave method are performed. The formation energies for different defects are calculated as a function of the atomic chemical potentials of constituent elements. We compare the formation energies for the NAs substitution and split interstitial complexes based on the traditional (100) and high-index GaAs (311) A/B plane under Ga-rich and As-rich conditions. According to the results of comparison, the chemical potential condition of forming-related defect and the dominant defect for all planes are determined. [ABSTRACT FROM AUTHOR]

Precursor design plays an important role in preparing high-quality Cu 2 ZnSn(S, Se) 4 (CZTSSe) absorber layers via solution coating method. In this work, SnCl 4 and SnCl 2 with different molar ratios were utilized as Sn source in the precursor solution to investigate effects of Sn oxidation state on the film growth process and the related solar cell device performance. Sn4+-rich and Sn2+-rich precursors were found to follow different reaction paths in obtaining CZTSSe grains, thus resulting in quite different crystallinity and morphology of the absorber. For Sn4+-rich precursor system, the direct Se substitution reaction of macroscopically disordered CZTS precursor calls for relatively high temperature to eliminate the double-layer structure and form large-size CZTSSe grains. For Sn2+-dominated precursor solution, however, the reaction of binary compound phases with the catalysis of low-melting-point Sn(S, Se) 2 prefers relatively low temperature during the selenization process. The work demonstrates that both types of precursors (or reaction paths) could actually lead to high-quality CZTSSe absorbers and solar cell devices with conversion efficiency higher than 8%, upon the proper selection of selenization conditions. • SnCl 4 and SnCl 2 with different molar ratios were utilized in the precursor solution to prepare CZTSSe films. • Sn4+-rich and Sn2+-rich precursors follow different reaction paths in obtaining CZTSSe grain. • Proper selection of selenization temperatures according to the Sn4+/Sn2+ content ratio is important. [ABSTRACT FROM AUTHOR]

[Display omitted] • Continuous synthesis of Cs x Pb y Br z NCs were realized via a microfluidic system. • Cs x Pb y Br z perovskite NCs with tunable dimensionalities were achieved. • Stable CsPbBr 3 /Cs 4 PbBr 6 composite NCs exhibited bright emissions in solid forms. • Growth and luminescence mechanisms of Cs x Pb y Br z perovskite NCs were revealed. All-inorganic perovskite CsPbBr 3 shows great potential in optoelectronic device applications due to their excellent optoelectrical properties. However, its practical use is still dauntingly plagued by the poor stability. Recently, its derivatives Cs 4 PbBr 6 and CsPb 2 Br 5 featured with good stability and the versatility in crystal structure have emerged as promising alternatives. Nevertheless, synthesizing such a series of perovskites through a facile, scalable, and high-yield method is challenging, and their luminescence mechanisms are still elusive. Herein, we reported a facile and rapid method for continuous synthesis of Cs x Pb y Br z -based perovskites (including Cs 4 PbBr 6 , CsPbBr 3 /Cs 4 PbBr 6 , CsPbBr 3 , CsPbBr 3 /CsPb 2 Br 5 , CsPb 2 Br 5) via a microfluidic system. The transformations of different dimensional perovskite nanocrystals were realized by simply adjusting the precursor flow rate. CsPbBr 3 /Cs 4 PbBr 6 and CsPbBr 3 /CsPb 2 Br 5 composite nanocrystals exhibited bright emissions in their solid forms, where CsPbBr 3 nanocrystals uniformly embedded in Cs 4 PbBr 6 or CsPb 2 Br 5 matrix. Simultaneously, strong green fluorescence exclusively from CsPbBr 3 nanocrystals was detected and related energy transfer in composite nanocrystals was further investigated. Finally, the highly stable CsPbBr 3 /Cs 4 PbBr 6 nanocrystals were used for the construction of WLED with a wide color gamut of 131% NTSC. This work provides a novel path for large-scale and controlled synthesis of the ternary Cs-Pb-Br materials for specific light-emitting applications. [ABSTRACT FROM AUTHOR]

Cation doping is an important approach to improve the performance of kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) thin film solar cells. Since different cation dopant has different effects on the defects and crystallization of CZTSSe absorber, it is expected to achieve better device performance via the synergistic effects of double cation co-doping compared with the single cation doping. Herein, we investigated the effects of Ag/Ge co-doping on CZTSSe solar cells by doping Ge in an already optimized Ag-alloyed CZTSSe (ACZTSSe). It is found that incorporating a small amount of Ge can further improve the crystallinity and minority carrier lifetime of ACZTSSe. The low-temperature photoluminescence results reveal that the Ge doping primarily suppressed the Sn Zn defects in ACZTSSe, thereby further boosting the device performance. However, higher Ge doping concentration can lead to a discontinuous surface morphology, which is believed to be related with the relatively low melting temperature and double-layered structure of ACZTSSe absorber. The deteriorated surface morphology results in photocurrent loss in the near-infrared region and decreased fill factor. As the Ge doping ratio increases, there is a balance between the defects and morphology. A champion power conversion efficiency (PCE), 11.4%, was achieved for the Ag/Ge co-doped CZTSSe solar cells at Ge substitution rate of 3%. Compared with the single Ag doping, the average PCE was further promoted by 0.5% due to Ag/Ge co-doping. • Ge doping can further improve the crystallinity and TRPL lifetime of ACZTSSe. • Ge doping primarily suppresses the Sn Zn defects of ACZTSSe. • Ge doping in ACZTSSe leads to discontinuous surface morphology. • Better device performance was achieved by Ag/Ge co-doping. [ABSTRACT FROM AUTHOR]

Large open-circuit voltage deficit is still the main factor restricting the performance of kesterite Cu 2 ZnSn(S,Se) 4 thin film solar cells. The high concentration of Cu Zn defects and [2Cu Zn + Sn Zn ] defect clusters are believed to be the significant origins of severe band tailing of the kesterite absorber. A promising way to improve the open-circuit voltage and power conversion efficiency of the device is substituting Ag+ with a larger ionic radius for Cu+ to suppress the defects and construct a front-graded bandgap. However, the Ag doping in kesterite can significantly lower the melting temperature, which results in difficulties in forming an Ag grading distribution across the absorber due to the strong thermal diffusion. Herein, we innovatively introduce a ZnO insert layer in the precursor film, which is expected to slow down the Ag-Cu interdiffusion during the selenization, thereby forming a desired front-graded bandgap. The Ag grading distribution in absorbers is regulated by the thickness of ZnO insert layer. The effects of ZnO insert layer on the phase compositions, morphologies, optical properties, and photovoltaic performance of Ag-doped kesterite absorbers are investigated. [ABSTRACT FROM AUTHOR]

The ligand assisted reprecipitation (LARP) approach is a convenient method for synthesizing CsPbX3 NCs at room temperature. However, several remaining challenges limit its further development, such as the utilization of toxic solvents and fast crystallization brings colloidal uncontrollable synthesis issues. In this work we apply the principles of green chemistry to the LARP technique for synthesizing CsPbBr3 NCs under ambient conditions in a controllable way. Through the variation of non-toxic ester solvents with different polarity and reaction time, we demonstrate the size tunability of one-dimensional (1D) CsPbBr3 nanocrystals synthesized in a green solvent system. Due to the strong quantum confinement effect, the obtained CsPbBr3 NCs exhibited a wide photoluminescence emission (471–508 nm) and high quantum yield up to 78%. Interpretations on the related growth mechanism of CsPbBr3 nanocrystals in a polarity-mediated solution are suggested for exploring effective strategies towards high-quality inorganic perovskite nanocrystals with definite morphologies. Finally, to explore the potential applications of CsPbBr3 in white light-emitting diodes (WLEDs), cyan emission of CsPbBr3 NCs (480 nm) is combined with blue, green, and red emissions from commercial powders to achieve white light with excellent vision performance. The device displays a super high color rendering index of 96.5. [ABSTRACT FROM AUTHOR]

Solvent engineering is an important route for improving the quality of solution-processed copper-zinc-tin-sulfur-selenium (CZTSSe) thin films. Here, blended solvents composed of dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) were used to prepare CZTSSe precursor solution. The addition of DMF improved the wettability of precursor solution on Mo-coated substrates and modified the CZTSSe formation. Impacts of different DMF contents in solvents on morphological, structural, optical and photovoltaic properties of CZTSSe films were fully studied. Compared with the pure DMSO-based precursor solution, incorporation of an appropriate amount of DMF into DMSO can effectively increase the grain size and improve the film compactness, while adding excess DFM decreased the crystallinity and deteriorated the device performance. By optimizing DMF content, the carrier lifetime of CZTSSe thin film was increased from 2.78 ns to 5.07 ns and the energy conversion efficiencies of solar cells were improved from 4.77% to 6.03%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg(Ac) 2 was used as additive for the fabrication of CsPbI 2 Br perovskite films. • Mg(Ac) 2 could form strong binding with CsPbI 2 Br, leading to improved crystallization and passivation of defects. • Under optimized content of Mg(Ac) 2 , the carbon electrode based CsPbI 2 Br solar cells achieved a high efficiency up to 13.08%. Carbon electrode based hole transporting materials (HTM) free CsPbI 2 Br perovskite solar cells have advantages of excellent thermal stability and low cost. However, it is still a challenge to provide an effective strategy to realize highly efficient and stable HTM-free devices. Herein, a small amount (0.2–0.5% vs Pb source) of magnesium acetate (Mg(Ac) 2) was introduced into the CsPbI 2 Br precursor solution. It was demonstrated that the carbonyl groups of Mg(Ac) 2 can bind with all intrinsic elements of CsPbI 2 Br, leading to improved crystallinity and passivation of defects. Therefore, the power conversion efficiency of HTM-free devices was increased from 10.84% to 13.08%, along with an enhancement in device stability. [ABSTRACT FROM AUTHOR]

• Ag doping strategy is introduced into Cu 3 BiS 3 film. • Ag incorporation can enlarge the grain size and improve the film compactness. • Ag doping can increase the light absorption, band gap and carrier concentration. • Proper amount of Ag doping leads to the enhancements of both V OC and J SC. • An efficiency improvement of ~85% was realized just through Ag doping. Ternary compound semiconductor Cu 3 BiS 3 has been perceived as a potential candidate of solar absorber materials in recent years, due to the low–toxic and earth–abundant component elements as well as excellent optoelectronic properties. However, the fundamental properties vital for Cu 3 BiS 3 photovoltaic device have not been fully explored and the efficiency is still at an extremely low level. Herein, a cation doping strategy was introduced during preparing Cu 3 BiS 3 absorber layers to optimize the material properties and thereby improve the device performances. Basing on a one-step solution method, the effects of Ag doping on the structural, optical, electrical and photovoltaic behaviors of Cu 3 BiS 3 film were investigated in detail. Our results demonstrate that appropriate Ag doping can enlarge the grain size, improve the film compactness, enhance the light absorption, broaden the band gap and increase the carrier concentration of absorber layer. As a result, the photovoltaic performance is also evidently promoted, achieving a highest efficiency improvement of ~85% relative to the undoped Cu 3 BiS 3 solar cell device. Higher Ag incorporation, however, causes phase separation and dramatically deteriorates the absorber properties. [ABSTRACT FROM AUTHOR]

Recently, Cu3BiS3 has emerged as an attractive photovoltaic material with low cost and excellent light absorption. However, its device application is still hindered by relatively poor material quality. Here, a one-step solution method based on dimethyl sulfoxide (DMSO) and thiourea (TU) was used to prepare Cu3BiS3 thin films. The effects of TU dosage on the structural, optical and electrical properties of Cu3BiS3 were systematically discerned. The obtained Cu3BiS3 shows the band gap ranging from 1.40 to 1.68 eV and the carrier concentration in the order of 1016 cm−3. Although a stoichiometric overdose of TU was usually applied in preparing high-quality chalcogenide semiconductor films, our results illustrate that properly increasing concentration of TU in precursor solution enhances the grain size and carrier mobility, while much higher TU supply tends to deteriorate them. Correspondingly, the efficiency of device with the structure of Mo/Cu3BiS3/CdS/ZnO/ITO/Al exhibits the similar tendency. The best PCE of 0.291% occurs for the precursor solution with TU concentration of 3.0 M, and the corresponding VOC, JSC and FF values are 233 mV, 2.867 mA/cm2 and 43.552%, respectively. [ABSTRACT FROM AUTHOR]

The theoretical electron mobility limited by dislocation scattering of a two-dimensional electron gas confined near the interface of AlxGa1-xN/GaN heterostructures was calculated. Based on the model of treating dislocation as a charged line, an exponentially varied potential was adopted to calculate the mobility. The estimated mobility suggests that such a choice can simplify the calculation without introducing significant deviation from experimental data, and we obtained a good fitting between the calculated and experimental results. It was found that the measured mobility is dominated by interface roughness and dislocation scattering at low temperatures if dislocation density is relatively high (>109 cm-2), and accounts for the nearly flattening-out behavior with increasing temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • A MEA-DMF based S free solution for preparing CZTSe was successfully developed. • Phase evolution of CZTSe thin film during selenization was studied. • A device efficiency of 7.53% was obtained by using the MEA-DMF solution method. Most precursor solutions for preparing Cu 2 ZnSn(S,Se) 4 thin films use sulfur containing groups to complex metal ions. However, solutions with sulfur containing groups are always toxic and harmful gases, such as H 2 S and SO x , will be released when drying precursor films. Based on the excellent chelating ability of ethanolamine, a stable molecular precursor solution without using sulfur based complexing agent was successfully developed. Cu-Sn alloy phase is formed in the precursor film, which makes the phase evolution of the absorber during selenization similar to that of Cu 2 ZnSnSe 4 film grown from metallic precursor. Impacts of selenization time on compositional, morphological and photovoltaic properties of the Cu 2 ZnSnSe 4 film were studied. Finally, a Cu 2 ZnSnSe 4 solar cell with conversion efficiency of 7.53% was obtained by using the ethanolamine-dimethyl formamide based solution. [ABSTRACT FROM AUTHOR]

Most reported solution processed Cu 2 ZnSn(S,Se) 4 thin film solar cells are fabricated from precursor solution with sulfur source. However, the use of sulfur-containing solution is undesirable from the viewpoint of environment and security due to the release of sulfur-containing harmful gases when drying precursors. Here, a novel sulfur/selenium-free solution method using ethanolamine-dimethyl formamide as solvent was developed for the preparation of Cu 2 ZnSnSe 4 thin films. It was found that Cu-Sn alloy phases were formed in precursor during drying process. The formation and phase transition mechanisms of the Cu-Sn phases were illustrated. The aggregation level of the alloy phases and their distribution in the precursor depend on the drying time. Effects of different drying time on structural, morphological and photoelectric properties of the resulted Cu 2 ZnSnSe 4 films were systematically investigated. The Cu 2 ZnSnSe 4 absorbers exhibit a sandwiched structure or a four-layer structure, which is determined by the drying time of precursor, implying two different grain growth mechanisms. The devices with drying time of 6 min show larger grain size, longer carrier life time, higher external quantum efficiency and better average photovoltaic performance. [Display omitted] • A S/Se free pure solution method was developed for growing CZTSe thin films. • Formation and phase transition mechanisms of Cu-Sn alloys in precursor were investigated. • Short drying time of precursor leads to carbon-rich surface of CZTSe thin film. • Aggregation level of Cu-Sn phase affects absorber morphology and device performance. [ABSTRACT FROM AUTHOR]

Novel and advanced photocatalytic materials for water splitting are of huge interest due to the increasing global energy crisis. In this work, MoS2/g-C3N4 heterojunctions are prepared as high-performance photocatalysts for hydrogen evolution using solar energy. Benefiting from the elaborate ion exchange, uniformly dispersed MoS2 quantum dots with controllable size and a high loading amount grow in situ on the surface of g-C3N4 nanosheets through a simple hydrothermal process, and tight heterostructures are obtained at the interface between the two semiconductors. The quantization of MoS2 enhances its redox activity in water splitting, and the compact heterojunction facilitates the separation of photoinduced charge carriers, resulting in efficient photocatalytic H2 production at the MoS2/g-C3N4 heterojunction. This work highlights ion exchange as a facile and effective method for obtaining high efficiency MoS2/g-C3N4 heterojunction photocatalysts. [ABSTRACT FROM AUTHOR]

Fluorinated graphene quantum dots (FGQDs) have distinctive charge distribution in structure and unique chemical bonds in composition, corresponding to novel performance different from common quantum dots. However, their synthesis is a challenge due to chemically inert C F bonds and hydrophobic nature, and the fluorine influence on FGQDs remains scarce and to be studied. Herein, we first design a gradient fluorine-sacrificing strategy to synthesize FGQDs with controllable sizes and tunable fluorine contents from bulk fluorinated graphite. It is found that although fluorine atom is the second-smallest in periodic table, it not only greatly affects the size formation process, but also endows FGQDs with pH-independent luminescence without any additional surface passivation. And it is for the first time to experimentally observed that point defects in FGQDs induced by fluorine can greatly increase paramagnetism, which is 5 times higher than unfluorinated ones. Moreover, cytotoxicity experiments clearly reveal FGQDs show good biocompatibility, and it is the chemical surface rather than size that influences the cell viability. This work realizes fine control over both structure and chemistry of FGQDs, and thus allows a better insight into the fluorine effects on formation and performance of graphene quantum dots. [ABSTRACT FROM AUTHOR]

In this article, a novel Ag2S nanoparticle-decorated MoS2 composite (A@M) was synthesized through a facile in situ growth of the monoclinic crystallographic Ag2S on MoS2 nanosheets. The A@M composite was used as a catalyst in water splitting which exhibits higher electrocatalytic and photoelectrocatalytic activity than the respective pure MoS2 and Ag2S counterparts. Experimental results indicate that the as-prepared A@M composite with an optimal Ag2S/MoS2 molar ratio of 16.30% (16%A@M) shows the best catalytic performance with low overpotentials (110 mV for Voc, 190 mV for onset overpotential, 208 mV for the current density of 20 mA cm−2), a small Tafel slope (42 mV dec−1), and a high photocurrent (82 μA cm−2 under an applied potential of 0.4 V). The enhanced electrocatalytic activity is associated with the improved electrical conductivity resulting from the stretched MoS2 nanosheets and the enriched active sites due to the decorated Ag2S particles. The formation of a type II heterojunction structure at the interface between Ag2S and MoS2 facilitates the separation of photogenerated charge carriers, and thus is responsible for the enhanced photoelectrocatalytic activity and photocatalytic H2 production rate (628 μmol h−1 g−1). This work suggests a promising choice to overcome the intrinsic drawbacks of MoS2 nanostructures for the application in hydrogen evolution. [ABSTRACT FROM AUTHOR]

The authors describe the preparation of Fe(MoO) materials with micrometer dimensions, and show that they are highly efficient peroxidase mimics that can be used in a photometric assay for HO. Depending on the experimental conditions of synthesis, the Fe(MoO) micromaterials display different morphologies, surface properties, and peroxidase-like activities. Among them, Fe(MoO) with flower-like structure has the largest BET specific surface area and the most negative potential. It exhibits the best peroxidase mimetic activity in catalyzing the oxidation of 3,3′,5,5′-tetramethylbenzidine in the presence of HO to generate a blue-green product. Based on these findings, method was worked out for HO determination that allows both visual and photometric read-out. The assay has a detection limit as low as 0.7 μM, is selective and practical. Given its sensitivity, the method has a good potential with respect to determination of HO in clinical samples but also in oxidase-type of reactions where HO is being produced. [ABSTRACT FROM AUTHOR]