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Fe3O4 nanoplates were fabricated by an anodic oxidation process and a subsequent water assisted crystallization process at low temperature, which was found to be very efficient and environmentally friendly. The as-prepared Fe3O4 nanoplates have hexagonal outlines with a thickness of about 20 nm. Tremendous grooves were distributed on the entire surfaces of the nanoplates, making the two-dimension nanoplates have a unique 3D morphology. Transmission electron microscopy results confirmed that the single-crystalline nature of the nanoplates was well maintained. Owing to the unique structures and porous morphologies, the as-prepared 3D nanoplates show excellent ability for absorbing solar energy and absorbing organic pollutants, which can be utilized for cleaning up water. Moreover, the Fe3O4 nanoplates show good magnetic properties that enable them to be easily collected and recycled. We believe this study will inspire the application of Fe3O4 nanoplates with 3D structures in energy and environmental areas.

A novel and elegant hydrophilic/hydrophobic nanoporous double layer structure was designed and developed for efficient long-term water desalination. It contained a hydrophobic salt-resistant hierarchical layer of well-defined Cu2SnSe3 (or Cu2ZnSnSe4) nanosphere arrays for broad solar harvesting and water vapor evaporation, and a hydrophilic filter membrane for continuous water supply and vapor generation. The as-fabricated self-floatable devices achieve remarkable solar water evaporation performances (average evaporation rate: 1.657 kg m−2 h−1 and solar thermal conversion efficiency: 86.6% under one sun) with super stability for water distillation from seawater and wastewater containing organic dyes, heavy metals and bacteria.

Solar steam generation is a renewable, environmentally friendly and low-cost technology for seawater desalination and wastewater remediation. Highly efficient solar evaporation from pure water has been achieved using advanced artificial architectures and hydrophilic light absorption materials, while the long-term steady work for high salinity water desalination becomes a non-negligible problem when it comes to practical use. In terms of this issue, a hydrophobic MXene membrane, which contains a salt-blocking delaminated Ti3C2 nanosheet layer with trimethoxy(1H,1H,2H,2H-perfluorodecyl)silane modification for sunlight harvesting and a piece of commercial filter membrane for water supply, is proposed in this work. With high light utilization, high stability, abundant evaporating channels, rapid water transport through the filter membrane and salt-blocking on the MXene membrane, the as-fabricated self-floatable device achieves a solar evaporation rate of 1.31 kg m−2 h−1 and a solar steam conversion efficiency of 71%, and stability under high salinity conditions under one sun over 200 hours, ensuring the highly efficient and long-term stable photothermal transduction for water purification from seawater and wastewater containing organic dyes and heavy metals. The hydrophobic surface enabled salt-blocking MXene membrane is proved to be an effective, efficient and stable photothermal material for solar desalination.

ZnO is an excellent semiconductor material for photocatalytic application. To overcome the photocorrosion of ZnO and improve its stability, nanorods (NRs) structured ZnO is prepared by an environment-friendly solid state synthesis method, and the composite of ZnO with different mass ratio of reduced graphene oxide (RGO) are obtained via a hydrothermal reaction. According to the photocatalytic results, 5% RGO composited with ZnO NRs degrades the methylene orange solution completely (98%) in 50 min under UV light irradiation, whereas bare ZnO NRs just degrade 40.9%. The transient photocurrent responses and electronical impedance spectroscopy tests are carried out to illustrate the mechanism of RGO in the nanocomposite for the enhancement of the photocatalytic performance. This composite of ZnO/RGO has demonstrated a great potential for high efficient and stable photocatalytic application.

We reported a facile fabrication of Bi 2 O 3 /carbon quantum dots (CQDs) photocatalysts. All the synthesized samples were characterized and investigated. Firstly, irregular β-Bi 2 O 3 nanosheets were obtained by a thermal treatment of Bi 2 O 2 CO 3 precursor at 350 °C for 3 h in air. Then, different contents of CQDs were incorporated onto the as-obtained β-Bi 2 O 3 nanosheets in ethanol solution by vigorous stirring. The experimental results demonstrated that the visible light absorption of β-Bi 2 O 3 photocatalyst is greatly enhanced with the incorporation of CQDs. Furthermore, the fabricated heterostructure photocatalysts exhibited an enhanced photocatalytic activity over the photodegradation of Rhodamine B under the irradiation of visible light, owing to the separation of the photoinduced electrons and holes.

Supercapacitor, as an important energy storage device, is a critical component for next generation electric power system, due to its high power density and long cycle life. In this study, a novel electrode material with quasi-core-shell structure, consisting of negatively charged few layer Ti3C2 nanosheets (FL-Ti3C2) and positively charged polyethyleneimine as building blocks, has been prepared by using an electrostatic layer-by-layer self-assembly method, with highly conductive Ni foam to be used as the skeleton. The unique quasi-core-shell structured ultrathin Ti3C2 nanosheets provide an excellent electron channel, ion transport channel and large effective contact area, thus leading to a great improvement in electrochemical performance of the material. The specific capacitance of the binder-free FL-Ti3C2@Ni foam electrodes reaches 370 F g−1 at the scan rate of 2 mV s−1 and a specific capacitance of 117 F g−1 is obtained even at the scan rate of 1000 mV s−1 in the electrolyte of Li2SO4, indicating a high rate performance. In addition, this electrode shows a long-term cyclic stability with a loss of only 13.7% after 10,000 circles. Furthermore, quantitative analysis has been conducted to ensure the relationship between the capacitive contribution and the rate performance of the as-fabricated electrode.

A mesoporous NiO x (m-NiO x ) film which is deposited from a precursor using solution-derived Ni(OH) 2 nanosheets as the starting material is employed as the hole transport layer to fabricate the perovskite solar cell. A simple annealing process at 500 °C in air decomposes the Ni(OH) 2 nanosheets into NiO x nanoparticles, removes organic components, and produces nanopores in the film, leading to the formation of m-NiO x films at once. Results indicate that the annealing time has a great effect on the morphology and crystallinity of the resulting m-NiO x films, and prolonging the annealing time leads to smaller NiO x nanoparticles, bigger pores and higher crystallinity, which contribute to a better device performance. After a careful optimization, the highest power conversion efficiency of 11.97% is achieved on the device based on the m-NiO x film annealed at 500 °C for 3 h. This work provides a new method to prepare efficient m-NiO x films for high performance perovskite solar cells.

Moisture has been reported to be positive for organic-inorganic halide perovskite films formation during their annealing process in several literatures. Here we report a comprehensive study of moisture effect on the annealing process of CH 3 NH 3 PbI 3 films deposited by solvent engineering method. Perovskite intermediate phase films are deposited by spin coating in a glove box and then annealed in the glove box or air with different humidity. Different from previous reports, the presence of moisture dramatically deteriorates the film morphology, and too high humidity even retards the formation of the perovskite from its intermediate phase. However, the crystallinity, conductivity and optical properties of the films are greatly improved, which in turn contributes to a much better device performance. This work suggests that the effect of moisture annealing on perovskite films is closely related to the deposition method and composition, and the deterioration of surface morphology does not necessarily lead to worse device performance.

Developing flexible energy storage materials with high volumetric performances for portable electronic applications is arousing increasing interest in recent years. Herein, we presented a simple in-situ wet chemistry synthetic method to prepare flexible and free-standing MnO x -Ti 3 C 2 hybrid films, consisting of few-layered titanium carbide nanosheets and manganese oxide nanoparticles, which exhibited promising electrochemical performances as electrodes of supercapacitors. Hybridized nanoparticles of Mn 2 O 3 and MnO are anchored on the surface of delaminated Ti 3 C 2 nanolayers through electrostatic interactions. Such unique film based electrodes have a volumetric capacitance of 602.0 F cm −3 at 2 mV s −1 . Also, symmetric supercapacitors based on the MnO x -Ti 3 C 2 electrodes show an excellent energy stored capacity (13.64 mWh cm −3 ) and a very high long-term cycle stability with 89.8% capacitance retention after 10000 circles. Hence, these highly flexible and free-standing MnO x -Ti 3 C 2 films could be potential candidates as electrodes for flexible supercapacitors.

ZnO films are employed as the electron transport layers for perovskite solar cells. Such a device exhibits an ultralong time increase in Voc (∼100 s) and Jsc (∼1000 s) and a weakening hysteresis under continuous illumination. Besides, a slow (∼20 s) Voc decay when illumination is switched off is also observed. The electrical measurements performed under illumination and under voltage bias before being illuminated, suggest the influences of ionic accumulation/redistribution in causing above phenomena. Ionic accumulation happening in dark and ionic redistribution under illumination lead to band bending which affects the excitons separation and carrier extraction. These can account for the ultralong time increase in Voc and Jsc as well as the slow Voc decay. Also, the time-dependent photocurrent response under stepwise scan proves the presence of a capacitive effect in the device which can be dramatically reduced by the ionic redistribution under illumination. The ionic redistribution is also an important re...

Subject to the complexity and high cost of traditional semiconductor materials and manufacturing processes, the features of facile solution process with low cost have made the colloidal quantum dots (CQDs) more competitive, in which HgTe nanocrystals can be tuned as a potential in infrared region and achieve a great photoresponsivity. Herein, we reported the synthesis and characterization of HgTe CQDs materials by a facile solution process, and explored the relationship between the nanocrystal size and the reaction temperature and time, as well as the effect of the ligand exchange on the thickness of the HgTe CQDs film. The as-fabricated photoconductive device showed a high photoresponse even under a weak light, which provides a direction for the next-generation infrared photodetectors.

A chloroform-assistant Se dissolution in oleylamine without trioctylphosphine and alkylthiol as the green precursor was used for facile and robust synthesis of quaternary selenide nanocrystals. The S 2− modified hydrophilic Cu 2 ZnSnS 4 and Cu 2 ZnSnSe 4 nanocrystals were first prepared by a one-pot thermal decomposition route, followed by a bi-phase hydrophilic treatment process. As a proof of concept, the as-obtained hydrophilic nanocrystals were hybridized with ZnO microspheres as photosensitizers to achieve visible light-driven photocatalytic application; on the other hand, hybridized with NaYF 4 : Yb, Tm microplates to achieve near-infrared light-driven photocatalytic application. These photosensitized hybrids as photocatalysts expanded the light absorption from ultraviolet to visible even near-infrared region, which showed excellent photocatalytic Rhodamine B degradation under visible and near-infrared irradiation compared to pure ZnO and NaYF 4 : Yb, Tm, respectively. Therefore, these hydrophilic Cu 2 ZnSnS 4 and Cu 2 ZnSnSe 4 nanocrystals are proved as efficient photocatalytic sensitizers due to the efficient utilization of the visible light and emissions upconverted from near-infrared light.

Two-dimensional transition metal carbides (MXenes) were recently emerged as promising electrode materials for energy storage applications. Herein, we report a high-capacity supercapacitor material based on nitrogen-doped delaminated titanium carbides (N-d-Ti3C2) synthesized through the facile urea-assisted delamination of large-scale Ti3C2 and carbonization of delaminated Ti3C2 (d-Ti3C2) mixed with urea. The two-dimensional N-d-Ti3C2 nanosheets exhibit a high specific capacitance of 266.5 F g−1 at the scan rate of 5 mV s−1 in 6 M KOH electrolyte solution, with a high capacitance retention capability. This new type of nitrogen-doped delaminated titanium carbide could be a promising electrode material for high-performance supercapacitors.

Organometallic halide-based perovskite solar cells (PSCs) have attracted significant research attention among the next-generation photovoltaic technologies, in which the electron transport layer (ETL) plays a crucial role in the PSC performances of power conversion efficiency and long-term stability. Herein, we proposed a low temperature solution-processing route to prepare indium oxide thin films on ITO substrates with an acetylacetone-chelated precursor, which exhibit better film morphology, well-aligned band structure, and enhanced electron extraction capacity. As a result, the PSC fabricated from the as-prepared indium oxide film as the ETL shows a promoted maximum efficiency of 15.30% and steady-state efficiency of 14.39%, which are a record for indium oxide-based PSCs. More significantly, the indium oxide film shows minimum photocatalytic activity compared with ZnO and TiO2 films, which leads to excellent light and shelf-life device stability. After storage in the dark for three months, the power conversion efficiency of the unsealed PSCs based on the indium oxide films degrades slightly, which retain approximately 94% of their peak efficiency.

A new visible light responsive silver niobate photocatalyst AgNbO 4− δ was synthesized by using a low-temperature chemical precipitation method. X-ray diffraction (XRD) results indicated that the AgNbO 4− δ compound has a tetragonal scheelite (ABO 4 ) type structure. It has also an optical absorption edge at about 596 nm, corresponding to a bandgap of about 2.08 eV. In addition, its microstructure and element composition were studied by using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). Furthermore, its photocatalytic activities were evaluated in terms of degradation of Rhodamine B, showing that the as-prepared AgNbO 4− δ compound has higher photocatalytic activity than P25.

TiO 2 nanohexagon arrays (TNHAs) were grown by anodization of Ti foil in an electrolyte containing NH 4 F, and then the TNHAs were transferred onto FTO glass by using a drop of sol containing Ti(OBu) 4 for fabricating a front-side illumination cell. In order to improve the power conversion efficiency (PCE) of the as-fabricated dye-sensitized solar cells (DSSCs), ZnO was introduced into the TNHAs by a facile immersing method. The as-obtained ZnO/TiO 2 nanohexagon heterojunction was used as the photoanode for DSSCs, which is expected to have a low recombination rate and high absorption of light. Results indicated that the DSSCs based on the ZnO/TNHAs exhibit an enhanced current density and high PCE of 6.85% under 100 mW cm −2 illumination. Furthermore, electrochemical impedance spectroscopy showed that the ZnO/TNHAs heterojunction-based DSSCs have optimized electron properties, including longer electron lifetime, lower resistance to electron transport, and smaller probability for electron recombination as compared to the DSSCs fabricated from pure TNHAs as photoanode.

In2O3/Bi2Sn2O7 composite photocatalysts with various contents of cubic In2O3 nanoparticles were fabricated by using impregnation method. A thriving modification of Bi2Sn2O7 by an introduction of In2O3 was confirmed by using X-ray diffraction, UV–vis diffuse reflectance spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The samples composed of hybrids of In2O3 and Bi2Sn2O7 exhibited a much higher photocatalytic activity for the degradation of Rhodamine B under visible light, as compared with pure In2O3 and Bi2Sn2O7 nanoparticles. Optimized composition of the composite photocatalysts was 0.1In2O3/Bi2Sn2O7, which shows a rate constant higher than those of pure In2O3 and Bi2Sn2O7 by 4.06 and 3.21 times, respectively. Based on Mott-Schottky analysis and active species detection, the photoexcited electrons in the conduction band of In2O3 and the holes in the valence band of Bi2Sn2O7 participated in reduction and oxidation reactions, respectively. Hence, OH, O2− and h+ were the main active species involved in the photocatalytic reaction of the In2O3/Bi2Sn2O7 composite photocatalysts. The effective separation process of the photogenerated electron-hole pairs was testified by photocurrent test.

A solvothermal method is employed to synthesize NiO x nanoparticles with good dispersibility. The synthesized NiO x nanoparticles are very homogenous with an average size of about 3–5 nm, and the X-ray diffraction suggests a good crystallinity for the nanoparticles. NiO x films are spin coated from a colloid precursor which is prepared by dispersing the NiO x nanoparticles into ethanol using a certain amount of acetic as the stabilizer. To obtain an efficient hole extraction layer, an annealing process at 300 °C degree is necessary to remove the residual acetic in the NiO x film. Finally, hysteresis-less NiO x -based perovskite solar cells with good reproducibility are achieved, and a highest power conversion efficiency (PCE) of 16.68% and a constant steady state PCE of 16.49% are also demonstrated.

Planar heterojunction perovskite solar cell promises low cost solution manufactured solar cells with the efficiency of single crystal silicon cells. However, it is still a great challenge to fabricate high quality perovskite films by solution method. Here, we demonstrate a simple method to control the morphology of perovskite film deposited on the top of a PEDOT: PSS coated ITO glass. The key to the process is to induce a change at the stage of the nucleation of intermediate phase, leading to the homogenous high density nucleation of the particles without preferred orientation instead of the sparse nucleation of the needle shaped crystals by a solvent treatment using a solvent which is miscible with the solvent of the perovskite precursor solution, but less soluble to the precursors of PbI 2 and CH 3 NH 3 I. The morphology of the intermediate phase determines the morphology of final perovskite film. Planar inverted heterojunction perovskite solar cells fabricated using the perovskite films deposited by the method as the absorb layer show a reproducible efficiency of 13.1%.

Antimony selenide (Sb2Se3) is a promising light-absorbing material for the thin-film solar cells (TFSCs). However, the low efficiency output of the Sb2Se3-based TFSC is still one of the largest obstacles to restrain its development. In this work, tin oxide (SnO2) nanoparticle film is used as the electron transport layer (ETL) for the Sb2Se3-based TFSC. To further enhance the device performance, spin coated CdCl2 films are employed to modify the SnO2 ETL. As a result, preferable orientation with an increased intensity of (2 2 1) peak and a reduced intensity of (1 2 0) peak in the XRD patterns are observed for the Sb2Se3 film, which enhances the carrier transport within the Sb2Se3 absorber. Meanwhile, the CdCl2 suppresses the carrier recombination at the interface between the Sb2Se3 and SnO2. Therefore, the optimized device shows an improved power conversion efficiency from 2.02% to 4.03%, and also exhibits a strong stability in ambient air.

Constructing multifunctional hierarchical nanocomposites is a promising strategy for enhancing the structural stability and electrochemical reaction kinetics of electrode materials. Herein, the two-dimensional (2D) hierarchical NiCoS/d-Ti3C2 composite is successfully synthesized through a co-precipitation and in situ sulfuration process, and shows interconnected porous network of NiCoS nanoplates on 2D d-Ti3C2 nanosheets. Interconnected porous network of NiCoS nanoplates can provide large surface area and rich open pores, thus leading to much redox reaction sites, while 2D d-Ti3C2 nanosheets with high conductivity can not only act as conductive channels for charge transfer rapidly, but also alleviate volume change of NiCoS. Benefited from the synergistic interaction between two components, the NiCoS/d-Ti3C2 composite electrode exhibits an enhanced specific capacity of 758.9 C g−1 at a current density of 1 A g−1 and good rate capability. The assembled hybrid supercapacitor (HSC) by using NiCoS/d-Ti3C2 composite as positive electrode and activated carbon (AC) as negative electrode delivers a high energy density of 22.6 Wh kg−1 at the power density of 0.4 kW kg−1 based on the total mass of active materials, and shows a good cycling stability. Our work provides a prospective and feasible strategy for the fabrication of hierarchical transition metal sulfides-based composites for high-performance supercapacitors.

Halide CsPbX3 perovskites, superior photovoltaic materials with great thermal endurance, are of tremendous passion for tunable bandgaps and gratifying applications in colored-light-emitting diodes (LEDs) and tandem solar cells (TSCs). Nevertheless, the inferior moisture tolerance for cubic (α)-phase perovskite is still a huge obstacle for sustaining output of CsPbX3-based perovskite solar cells (PSCs) under ambient pressure. For the representative CsPbIBr2 perovskite, the solution-derived film, enduring the disappointing quality for the existing voids and pinholes, severely limits its device performance and long-time outputs. Herein, we introduced a perovskite surface modification method, overspreading anion-exchanged CsPbIBr2 alloy quantum dots (QDs) over the bulk materials, to protect interior CsPbIBr2 perovskites by moisture isolation. As a reward, this attempt can help the thin perovskite films and associated devices against the ambient environments to achieve a superior stability, as well as a gratifying efficiency improvement of ~12% (8.16% vs. 7.31%) due to the defect passivation. Particularly, the QDs-modified perovskite films can still remain ~78% absorption after a two-stage storage of low humidity (~36%) and high humidity (~80%), comparing with a complete phase transformation (α → β) of the conventional films.

As a promising electron transport layer (ETL) material, tin oxide (SnO2) has been widely used for high-quality perovskite solar cells (PSCs). To further raise power conversion efficiency (PCE) of the PSCs, it is critical to improve the performance of SnO2 film. Herein, a facile method is proposed to tailor the properties of SnO2 ETL by treating it with ethanol vapor during the annealing process. With such treatment, the conductivity and electron mobility of SnO2 film are improved. More impressively, the absorption intensity of the perovskite film deposited on the ethanol vapor-treated SnO2 (E: SO) shows an increase, and the defect states are also effectively passivated. Thus, the VOC and FF of the devices based on the E: SO are greatly improved. Finally, the device achieves a champion PCE of 17.66%, which is superior to the control device of 16.62%. The results demonstrate that ethanol vapor annealing treatment is an effective method for improving the performance of photovoltaic devices based on SnO2 ETL.

[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is usually used to passivate the trap states and ion defects for suppressing hysteresis in both normal and inverted perovskite solar cells. Here, we find that the normal cell with the perovskite film fabricated on the PCBM film shows an evident hysteresis, while the inverted cell with the perovskite film covered by the PCBM film shows nearly no hysteresis, and the PCBM-Perovskite interface impacts on the hysteresis vastly. The poor PCBM surface wettability results in an inefficient carrier extraction at the interface and a red-shift of photoluminescence emission for the perovskite film coated on the PCBM film, which results from the plentiful trap states and ion defects inside the perovskite film due to its poor crystallization. Thus, the trapping/de-trapping processes and slow ion migration eventually lead to the hysteresis. For the perovskite film covered by the PCBM film, due to the good wettability of the perovskite film, PCBM molecules easily permeate into the perovskite film to passivate the trap states and ion defects, which improves the carrier extraction and thus eliminates the hysteresis of the inverted cell.

To enhance rate and cycle performances of nickel sulfide, the two-dimensional (2D) titanium carbide (Ti3C2, MXene) with good electrical conductivity and electrochemical stability is chosen as 2D supporting matrix for synthesizing nickel sulfide/delaminated Ti3C2 (Ni–S/d-Ti3C2) nanohybrids by a solvothermal method. The Ni–S/d-Ti3C2 nanohybrids show a coexistence of Ni3S2 and NiS with the characteristic peak of d-Ti3C2 nanosheets, and have electroactive species-on-sheet structures. The optimal Ni–S/1d-Ti3C2 nanohybrid delivers a high specific capacity of 840.4 C g−1 at 1 A g−1 with enhanced capacity retention of 64.3% at 30 A g−1 and an outstanding cycle performance, which are ascribed to an integration of d-Ti3C2 nanosheets that can act as electric channels to accelerate electrons transport at interface of the nanohybrid during charge-discharge processes. An increased Ni2+ content and BET surface area also contribute to redox reactions of Ni–S/1d-Ti3C2 nanohybrid electrode. An asymmetric supercapacitor (ASC) fabricated by using the Ni–S/1d-Ti3C2 nanohybrid as positive electrode and d-Ti3C2 film as negative electrode exhibits an energy density of 20.0 Wh kg−1 at 0.5 kW kg−1 and a good cycling stability. Our work provides a favorable ingenuity for synthesizing advanced nickel sulfide-based nanohybrids and an alternative strategy of using 2D MXene as capacitive electrode for high-performance supercapacitors.

Solar cells based on organometallic perovskite materials have been intensively investigated as the most promising next-generation photovoltaic technology. The quality of perovskite film and the heterojunction between perovskite and charge transporting materials dominate the performance of resulting devices. Herein, we report a facile additive-assisted method to form perovskite/2, 2', 7, 7'-tetrakis (N, N-di-p-methoxyphenylamine)-9, 90-spirobifluorene (spiro-OMeTAD) graded heterojunction by one step instead of spin-coating two layers separately. The additives concentration in anti-solution is optimized to form a mixed layer where spiro-OMeTAD is dispersive in upper perovskite films with a vertical gradient, and a capping layer with appropriate thickness. The incorporation of spiro-OMeTAD in anti-solution tremendously improve the crystallinity of perovskite films while the graded heterojunction and the derived capping layer contribute to reduced interfacial losses. Moreover, poly(methyl methacrylate) as the second additive in anti-solution further passivates defects in perovskite films. As a result, we realize perovskite solar cells with a power conversion efficiency of 15.72% based on perovskite-graded heterojunction, which is far beyond the control devices. This study demonstrates an effective extension of heterojunction engineering to fabricate efficient perovskite solar cells using simplified procedures.

Ag2O-Bi2Sn2O7 composites were prepared by a chemical co-precipitation method. The microstructural, morphological and optical properties of the as-prepared composites were characterized and studied. Effects of Ag2O contents on photocatalytic activity of the Ag2O-Bi2Sn2O7 composites were also investigated in detail. Compared with pure Bi2Sn2O7, the 0.03Ag2O-Bi2Sn2O7 composite exhibits the highest photocatalytic activity for the degradation of Rhodamine B aqueous solution under visible light irradiation. The enhanced photocatalytic activity of the Ag2O-Bi2Sn2O7 composite can be attributed to the existence of the Ag2O-Bi2Sn2O7 heterojunction, which is propitious to an effective separation of the photogenerated electron-hole pairs.

A petal-shaped Nb2O5 nanosheet thin film was grown directly on a transparent conductive fluorine-doped tin oxide (FTO) glass substrate via a facile hydrothermal method. Structural and morphological characterization showed that the Nb2O5 nanosheets with a thickness of about 30 nm stood almost vertically on the FTO glass substrate. The vertical thickness of the petal-shaped Nb2O5 nanosheet array film, which grows along (020) and (003) crystal planes, was 2–3 μm. The petal-shaped Nb2O5 nanosheet array film on FTO glass without annealing showed excellent photocatalytic activity for degrading aqueous rhodamine B. The activity was better than that of the porous P25 film with a thickness of 50 μm. The new architecture is suitable for reuse in photocatalytic applications.

ZnO nanorod array films grown on fluorine-doped tin oxide glass substrates were homogeneously coated with visible light responsive Cu2SnS3 nanoparticles through a controllable one-step electrodeposition process. The coating of Cu2SnS3 nanoparticles expanded light utilization from the UV to visible region and facilitated charge generation, separation and transportation, thus leading to significantly enhanced photoelectrochemical and photocatalytic performance. The ZnO/Cu2SnS3 nanorod array films with a deposition time of 90 s had the highest apparent rate constant (3.87 × 10−2 min−1) and photocurrent density (0.46 mA cm−2), which were 2.86 and 23.00 times that of the pure ZnO, respectively. The ZnO/Cu2SnS3 nanorod array films were proven to be an advanced structure for photoelectrochemical and recyclable photocatalytic applications due to the maintenance of the optimized Cu2SnS3 nanoparticle coating and array nanostructure.

Up-conversion β-NaYF4:Yb(3+),Tm(3+)/NaYF4 core-shell nanoparticles (NYF NPs) with a high luminous intensity in the visible light region were synthesized by a hydrothermal reaction process. Photocurrent densities of the mesoscopic perovskite solar cells fabricated by incorporating up-conversion NYF NPs into the electron transporting layer are effectively enhanced. The effects of the thicknesses of the electron transporting layer and the weight ratio of up-conversion NYF NPs/TiO2 on the power conversion efficiency (PCE) of the as-fabricated devices were also investigated. The results indicate that the PCE of the optimized device achieves 16.9%, which is 20% higher than that of the device without introducing NYF NPs, and the steady-state PCE of the as-fabricated devices is close to its transient-state PCE. The up-conversion effect of NYF NPs is conducive to higher device performance rather than the nanoparticles as scattering centers to increase possible light absorption of the perovskite film or the electronic effect of the NaYF4 shell surface. These results can be further confirmed by finite-difference time-domain simulation. Photoluminescence results suggest that the multiphonon-assistance can accelerate the nonradiative recombination process at a lower temperature. Incorporating NYF NPs into the electron transporting layer opens a new approach to a promising family of electron transporting materials for mesoscopic perovskite solar cells.

Anatase TiO2 nanohexagon arrays were grown by using an anodization process of Ti foil in fluoride containing electrolytes. Photoanode based on the as-grown anatase TiO2 nanohexagon arrays for DSSCs showed a power photoconversion efficiency of 4.01% and incident photon-to-current conversion efficiency of 68%, which are significantly higher than those of the device based on anatase TiO2 nanotube arrays. This improvement in power conversion efficiency should be attributed to the fact that the nanotubes with hexagonal structure have higher surface area to allow the uploading of more dye molecules for light harvesting. Also, the spacing introduced inside the hexagon might allow the dye molecules to cover the interior of the walls. In addition, it is believed that the photoconversion efficiency can be further increased by optimizing the hexagonal structure through the electrochemical conditions.

Novel H3ONb3O8–CuNb3O8 (HN–CN) semiconductors with a configuration of rod-like heterojunction were formed through analogous self-growth process, including ion-exchange and crystal structure transition processes. A p-type CuNb3O8 nano-semiconductor was grown on a layer structured rod-like KNb3O8 crystal and the as-prepared HN–CN sample showed a broad absorption range (~800 nm). Especially, the HN–CN sample exhibited an improved photocatalytic activity for hydrogen production, and a model was proposed to explain the improvement in photocatalytic activity. Current study may provide a new way for the preparation of the p–n heterojunction with high performance under visible light.

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The role of TiO2 thin films deposited by atomic layer deposition on p-InP photocathodes used for solar hydrogen generation was examined. It was found that, in addition to its previously reported corrosion protection role, the large valence band offset between TiO2 and InP creates an energy barrier for holes reaching the surface. Also, the conduction band of TiO2 is well-aligned with that of InP. The combination of these two effects creates an electron- selective contact with low interface recombination. Under simulated solar illumination in HClO4 aqueous electrolyte, an onset potential of >800 mV vs RHE was achieved, which is the highest yet reported for an InP photocathode.

ZnO microspheres synthesized by a hydrolysis method were sensitized with Bi2Sn2O7 (BSO) nanoparticles prepared using a hydrothermal method at different concentrations. Various characterization methods were employed to study the microstructural, morphological, optical and photocatalytic properties of the BSO-ZnO heterostructures. The effect of the BSO concentration on the photocatalytic activity of the as-prepared samples was also investigated. The 12.5BSO-ZnO sample exhibits the highest photocatalytic efficiency. The enhanced photocatalytic efficiency is ascribed to an effective separation of the photogenerated electrons and holes due to the presence of the BSO-ZnO heterojunction.

A hysteresis-less inverted planar heterojunction perovskite solar cell with 14.42% power conversion efficiency (PCE) was successfully fabricated by employing a solution-derived NiOx film as the hole selective contact. Here, the non-stoichiometric transparent NiOx film is composed of a lot of small NiOx nanocrystals with a cubic crystal structure. Inverted planar heterojunction perovskite solar cells based on the as-prepared NiOx hole selective contacts show a much higher PCE and air storage stability than the control device fabricated from the PEDOT:PSS film as the hole selective contact, since NiOx has a better electron blocking property due to its high conduction band edge position. The thickness of the NiOx contact strongly influences the performance of the NiOx-based perovskite solar cells, which include the PCE, hysteresis behaviors and air storage stability due to the thickness-dependent morphology of the NiOx contact.

Quantum dot-sensitized solar cells (QDSSCs) are one kind of promising photovoltaic devices for harvesting solar energy. Previous reports have studied various photoanode materials in order to achieve a high photoelectric performance, while little attention has been paid to the electrolyte system inside the QDSSCs. In this report, a polysulfide (S 2− /S x 2− ) electrolyte system was investigated and optimized based on a CdS quantum dot/ZnO nanowire solar cell and a CdSe/CdS co-sensitized QDSSC. Water–methanol mixed solution was taken as the solvent for this polysulfide electrolyte, considering simultaneously the penetration ability and the ion dissociation of the electrolyte. Electrochemical impedance spectra (EIS) measurement was used to investigate the impedance of the electrons recombination with the electrolyte at the photoanode/electrolyte interface. With the measured efficiency of the CdS-QDSSCs, the optimal composition of the electrolyte can be obtained. The work facilitates the development of highly-efficient electrolyte in the general field of quantum dot-sensitized solar cells.

We demonstrate an InP heterojunction solar cell employing an ultrathin layer (∼10 nm) of amorphous TiO2 deposited at 120 °C by atomic layer deposition as the transparent electron-selective contact. The TiO2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. A hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm2 and a high power conversion efficiency of 19.2%.

Sparse ZnO nanorod arrays (NRAs) are fabricated on transparent conducting oxide coated glass substrates by using a modified liquid phase epitaxial growth method. By adjusting the polymer concentrations and the spin-coating parameters, full infiltration of poly(3-hexylthiophene) (P3HT) into the as-prepared ZnO NRAs is achieved at 130°C in vacuum. A third component is incorporated into the P3HT/ZnO NRAs ordered bulk heterojunctions (BHJs) either through ZnO surface modification with N719 dye or CdS shell layer or by inclusion of a fullerene derivative into the P3HT matrix. Experimental results indicate that performances of the hybrid solar cells are improved greatly with the incorporation of a third component. However, the working principles of these third components differ from one another, according to morphology, structure, optical property, charge transfer and interfacial properties of the composite structures. An ideal device architecture for hybrid solar cells based on P3HT/ZnO NRAs ordered BHJs is proposed, which can be used as a guidance to further increase the power conversion efficiency of such solar cells.

The development of low-resistance source/drain contacts to transition-metal dichalcogenides (TMDCs) is crucial for the realization of high-performance logic components. In particular, efficient hole contacts are required for the fabrication of p-type transistors with MoS2, a model TMDC. Previous studies have shown that the Fermi level of elemental metals is pinned close to the conduction band of MoS2, thus resulting in large Schottky barrier heights for holes with limited hole injection from the contacts. Here, we show that substoichiometric molybdenum trioxide (MoOx, x < 3), a high work function material, acts as an efficient hole injection layer to MoS2 and WSe2. In particular, we demonstrate MoS2 p-type field-effect transistors and diodes by using MoOx contacts. We also show drastic on-current improvement for p-type WSe2 FETs with MoOx contacts over devices made with Pd contacts, which is the prototypical metal used for hole injection. The work presents an important advance in contact engineering of TM...

Interfacial water evaporation through solar heating with photothermal materials is a promising strategy for seawater desalination and wastewater purification. Tightly packed 2D membranes with high reflection losses and limited vapor escape channels result in a low evaporation rate. In this work, 3D MXene architecture was fabricated by dropping the delaminated Ti3C2 ([Formula: see text]-Ti3C2) nanosheets onto the carbonized melamine foam (CMF) framework. Owing to the macroporous 3D architecture, more effective broadband solar absorption and vapor escaping were achieved. As a result, the 3D CMF@[Formula: see text]-Ti3C2-based evaporator delivers a water evaporation rate of 1.60[Formula: see text]kg/m2[Formula: see text][Formula: see text][Formula: see text]h with a solar-to-vapor conversion efficiency of up to 84.6%.