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The cost-effective processability and high stability of carbon-based perovskite solar cells (C-PSCs) have shown great potential to positively devote to the development of large-scale production processes. However, there are certain critical issues such as inferior performance and poor interface contact between perovskites and carbon electrodes, which have to be resolved first. The review shows that three main carbon materials, namely, carbon black, graphenes and carbon nanotubes display high photoelectric conversion efficiencies when being mixedly used as rigid electrodes and show excellent robustness in mechanical deformation as flexible carbon electrodes in carbon-based perovskite solar cells. Moreover, the specific development of and the comparison among three primary types of C-PSCs, namely, meso C-PSCs, embedment C-PSCs and paintable PSCs are emphasized. Furthermore, this work discusses the latest progress of C-PSC interface engineering from four aspects, namely, energy alignment, hysteresis effect, interface passivation and built-in electric field, and the differences among them are explained. Finally, further challenges and perspectives of C-PSCs are outlined. This work will be a profound influence and guidance on the significance of C-PSCs in commercialization.

Nickel oxide (NiOx) film is employed to replace PEDOT:PSS as the hole transport layer for the inverted perovskite solar cells (PSCs) with Zinc Oxide as electron transport layer, and we focus on the...

The reversible activation process, which involves electron transfer from adjacent redox mediators to cofactors, the reversible chemical state change of cofactors, and the functional/structural change of redox mediators, is one of the most significant features of biological enzymes, and has inspired the design of homogeneous catalysts. However, for heterogeneous catalysts, such enzyme-like characteristics have been only observed in very few transition metal–organic frameworks (MOFs) and single copper atom incorporated TiO2 catalysts during dynamic photocatalytic processes, and have never been seen in industrially important visible light-driven narrow-band gap semiconductor catalysts. Herein, we first report on the design and synthesis of highly active CdS/Co–N redox catalysts through the pyrolysis of trithiocyanuric acid cadmium-cobalt (CdCoTMT) coordination polymers as single-source precursors, which exhibit a reversible photoactivation process. This unique design and synthetic strategy provide a platform that facilitates atomic-level anchoring control of cofactor transition metal atoms (Co2+ and Ni2+), reversible modulation of the macroscopic optoelectronic properties of CdS and enhancement of photocatalytic hydrogen evolution, promoting the practical application of conventional heterogeneous catalysts.

The development of non-noble metal electrocatalysts with high performance for the oxygen evolution reaction (OER) is highly desirable but still faces many challenges. Herein, we report a facile and controllable strategy to fabricate N-doped titanium carbide flakes (Ti3C1.8N0.2 and Ti3C1.6N0.4) using an in situ nitrogen solid solution, followed by an etching process. The introduction of nitrogen is beneficial to the Ti3C1.6N0.4 flakes for more exposed active sites, accelerated charge transfer upon an electrochemical reaction, and improved wettability for more accessible sites. As a result, the as-obtained Ti3C1.6N0.4 catalyst exhibits enhanced electrocatalytic properties for OER, which include a small ηonset of 245.8 mV, low Tafel slope of 216.4 mV dec−1, and relatively good catalytic stability. The present work not only deepens the understanding of in situ N-doped MXene electrocatalysts, but also provides a guideline for the preparation of other N-doped MXene-based hybrid materials for other renewable energy applications.

To acquire better nitrogen doping results of titanium carbides (MXenes), methanol (MT) solvent with high fluidity and smaller micromolecule size is selected to assist the introduction of nitrogen o...

The anti-fouling copper-zinc-tin-selenide (CZTSe) nanocarambolas were synthesized and deposited on a hydrophilic filter membrane, as the full solar spectrum absorber and nanoporous vapor generator, for efficient and stable solar-driven interfacial water evaporation. The CZTSe nanocarambolas assembled membrane based self-floatable device with excellent light-to-heat conversion, abundant nanochannels, anti-fouling property, timely water supply and low heat loss achieved a remarkable solar evaporation rate of 1.528 kg/m2 h and a solar-to-vapor conversion efficiency up to 86.4% under one Sun, and stable solar desalination over 30 days without decay. This assembled membrane showed an excellent salt-rejection ability and a potential application of long-term efficient, stable and safe solar water purification of seawater and wastewater, and practical freshwater production under natural conditions.

Designing a hybrid architecture of electroactive species on the modified graphene sheets is one of the most promising tactics for high-performance supercapacitors. Herein, multiphase nickel sulfides nanoparticles (Ni3S2-NiS, abbreviated as Ni-S-1) with abundant edge sites were synthesized by pyrolysis of three-dimensional porous Ni-C3N3S3 complexes, and then the N-doped graphene (NG)/Ni-S-1 hybrid was obtained by an introduction of graphene oxide. The NG/Ni-S-1 hybrid shows the electroactive species-on-sheet architectures and the heteroatom nitrogen doping into graphene. The unique structural composition of the NG/Ni-S-1 hybrid can accelerate the permeation and shorten the diffusion length of electrolyte ions, to perform favorable electrochemical charge storage kinetics. Remarkably, compared with Ni-S-1 electrode, the NG/Ni-S-1 hybrid electrode delivers an improved specific capacity of 732.1 C g−1 at 1 A g−1 and an excellent rate capability, which are attributed to more accessible surfaces and enhanced electron-transport capacity due to the integration of NG matrix. Furthermore, a hybrid supercapacitor assembled using the NG/Ni-S-1 hybrid as positive electrode and activated carbon (AC) as negative electrode demonstrates a high energy density of 40.2 Wh kg−1, high power density of 7.4 kW kg−1, and relatively good electrochemical stability. The facile strategy may offer a new opportunity for fabrication of transition metal sulfides-based hybrids for high-performance supercapacitors.

Low temperature derived carbon electrodes are employed to fabricate low cost hole transport layer free perovskite solar cells, in which perovskite films annealed in glovebox and ambient air are used as the absorbers, respectively. Results suggest that the air annealed sample has bigger crystal grains and higher crystallinity, and the existence of a small amount of lead iodide which passivates grain boundaries contributes to a lower trap density. As a result, a maximum power conversion efficiency (PCE) of 13.07% was obtained on the air annealed device, which is higher than those of devices annealed in glovebox (11.25%). Furthermore, the stability of unencapsulated devices stored in wet (with humidity around 90% ± 5%) air atmosphere are investigated and the results prove that our devices exhibit good stability. In addition to rigid devices, flexible perovskite solar cells are also fabricated using the same procedure. The highest PCE of 11.53% is demonstrated on the champion flexible device, and 69% of its initial PCE can be maintained even after 2000 bending cycles with a bending radius of 2 mm. Our work provides a promising and simple rout for low-cost, air-stable, high-efficiency carbon perovskite solar cells for both large area production and flexible electronic devices industry.

Devices with printable carbon electrodes are promising directions for the commercialization of perovskite solar cells. Most of perovskite solar cells employ mesoporous device structures when using printable carbon as the counter electrodes. Here, we carry a comparative study of planar and mesoporous perovskite solar cells with carbon electrodes. The device efficiency is significantly reduced from 11.37% to 5.27% when the mesoporous TiO2 film is removed from the device structure. Compared with the planar device, smaller carrier transport resistance and bigger carrier recombination resistance are demonstrated for the mesoporous device. Results suggest that the presence of mesoporous TiO2 enables an efficient electron extraction from the perovskite absorber, which remits the serious carrier recombination in the hole transport layer free device due to the hole accumulation. Therefore, the electron extraction efficiency is crucial in these hole transport layer free devices with carbon electrodes. This study helps to develop further optimization of low temperature carbon-based perovskite solar cells for higher reproducibility and higher device performance.

Oxygen evolution reaction (OER) is an important kinetic process in many important renewable energy applications, while high-efficiency electrocatalysts, especially efficient non-precious metal catalysts, are very essential to overcome substantial overpotential and sluggish kinetics of OER. Here, three-dimensional (3D) Ti3C2 based conductive network structure was firstly constructed by an absorption of 2D few-layer Ti3C2 flakes (MXene) onto 3D nickel foam (NF) network, and then ultra-small sulfur-incorporated nickel ferrite nanosheets (S-NiFe2O4) were grown on the 3D Ti3C2 based conductive network structure (abbreviated as S-NiFe2O4@Ti3C2@NF) by combining a facile thiourea-assisted electrodeposition process with a low-temperature calcination process. Results indicate that the as-fabricated S-NiFe2O4@Ti3C2@NF hybrid electrode exhibits a superior OER activity, which includes only 1.50 V vs. RHE to afford a current density of 20 mA cm−2, a Tafel slope of 46.8 mV dec−1 and excellent catalytic stability in 1 M KOH. Excellent OER performances are attributed to the favorable 3D hierarchical network structure and relatively fast electron transport provided by the few-layer Ti3C2 flakes matrix, good catalytic activity and abundant catalytic active sites from the ultra-small S-NiFe2O4 nanosheets, synergistically. This work could open a feasible way for achieving a new type of 3D MXenes based hierarchical network structure for renewable energy applications.

Trithiocyanuric acid trisodium salt hydrate (Na3TMT) has been proved an excellent heavy metal chelating agent and widely applied for heavy metal ions elimination in industrial wastewater. In this work, the chelating products of Bismuth(III) ion with this effective agent were prepared by solid state and liquid phase reactions, and proved as a new kind of n-type semiconductor. For full utilization of resource, the green and low-cost massive Bismuth chelate with good crystallinity, distinctive morphology, appropriate band structure and high stability was applied for photoelectrochemical application and photocatalytic organic pollutants degradation upon visible light. Results indicated that OH radicals were the main reactive specie in the photodegradation process. The combination of heavy metals and organic contaminants removal was achieved by a waste-to-wealth route.

Organometal halide perovskites (OHPs) are a kind of promising materials applied in solar cells. However, the toxicity of lead in OHPs is considered as an environmental problem. Herein, we report two lead-free two-dimensional (2D) iodide-based OHPs, namely (C6H16N2)2AgBiI8·H2O (AgBiI) and (C6H16N2)2CuBiI8·0.5H2O (CuBiI), where C6H14N2 = 1,4-cyclohexanediamine, with a double perovskite structure. These two bimetallic perovskites show the optical band gaps of 1.93 eV and 1.68 eV. In addition, these 2D perovskite materials can form smooth films through a simple one-step spin-coating approach. Photocurrent measurements under xenon lamp irradiation indicate obvious photoresponses, suggesting that these semiconducting materials have the potential for application in light harvesting.

Supercapacitors (SCs), environment-friendly high-power energy storage devices, have drawn great attention due to the increasing and urgent development of renewable energies. Ti3C2Tx (MXene), a 2D high conductivity material, has been shown to be a potential electrode material for SCs, because of its outstanding chemical and physical properties. However, the surface termination of –F and –OH could block the transport of electrolyte ions and thus decrease the energy storage performances. In this regard, nitrogen related functional groups have been introduced to modify the surface characteristics of Ti3C2Tx, in order to increase the electron conduction and energy storage capacity. Experimental results have shown that the presence of moieties such as –NH2, Ti–O–N and O–Ti–N, could offer a synergistic effect on the electrochemical performance of SCs, which is mainly attributed to the intercalation-pseudocapacitance contribution according to the quantitative analysis. Furthermore, the role of O–Ti–N is more significant than that of Ti–O–N. Specifically, for the first time, we demonstrate that electrodes based on the N surface modified Ti3C2Tx film display largely enhanced electrochemical performances, with gravimetric capacitance of 415.0 F g−1 at 2 mV s−1, rate capacity of 75.9% at 200 mV s−1 and cycling stability of above 90% retention after 18 000 cycles. In addition, symmetric SCs based on the N–Ti3C2Tx-300 film could deliver a maximum volumetric energy density of 21.0 W h L−1 and an energy density of 10.2 W h L−1, at a high power density of 18.3 kW L−1.

To achieve a reproducible perovskite film with full surface coverage, Zn 2+ ions are introduced to partially replace Pb 2+ ions in this work. Results indicate that the crystallization and formation of CH 3 NH 3 Pb 1−x Zn x I 3 film with micrometer grain size could be changed by the micro-strain for lattice shrink. The bandgap and optical properties of perovskite films are improved due to trace amounts of Zn 2+ ion dopant. More importantly, the solar cell device based on the Zn-doped perovskite film shows an increment in photocurrent of 21.13 mA cm −2 and power conversion efficiency (PCE) of 16.6%. Electrochemical impedance spectroscopy (EIS) measurements reflect that the charge recombination resistance and charge accumulation capacitance of devices based on MAPb 0.98 Zn 0.02 I 3 film are lower than that of the control device. However, present results also implied that MAPb 1−x Zn x I 3 films are still necessary to be extensively developed and optimized for further enhancing the device photovoltaic performance.

Ternary Cu2SnS3 (CTS) and Cu2SnSe3 (CTSe) quantum dots were grown in-situ on reduced graphene oxide (rGO) nanosheets by a facile one-pot colloidal synthesis. Possessing abundant active sites and having the ability to harvest solar energy and to facilitate charge separation, the CTS(e)/rGO 0D/2D nanocomposites showed remarkably enhanced photocatalytic activities for degradation of rhodamine B and methyl orange aqueous solutions upon visible light irradiation. The nanocomposites of rGO supported monodispersed quantum dots were proved to be a suitable platform for photocatalytic applications due to the well-maintained 0D/2D nanostructure.

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.

Indium oxide (IO) has been demonstrated as an efficient and stable electron transporting layer for planar heterojunction perovskite solar cells, but dispersive pinholes in the sol-gel derived IO film limit its hole blocking capacity and corresponding device performance. In this study, we introduce an ultrathin TiOx interlayer between Indium Tin Oxide (ITO) substrate and IO film via a low temperature TiCl4 treatment method. By optimizing the process time, we obtain the optimal perovskite solar cells with a 30 min TiCl4 treatment process, showing an impressive power conversion efficiency of 16.38%. In addition, the average device efficiency is improved from 13.7% to 15.1%, which is mainly attributed to the greatly improved fill factor. By means of investigating film roughness, pinhole effect and open circuit voltage decay, we find that the low-temperature processed TiOx interlayer efficiently enhance the hole blocking capacity of the electron transporting layer, and consequently boost the device performance.

A new ternary system consisting of ZnO nanorod/reduced graphene oxide (RGO)/CuInS2 quantum dots has been successfully prepared for photocatalytic application under visible light irradiation. Through the hybridization with the light harvesting material of CuInS2, as well as the conductivity medium RGO, the ternary composite achieves a greatly enhanced light absorption and charge transfer than that of the pristine ZnO. The photocatalytic performance of ZnO-RGO-CuInS2 is substantially elevated with an optimized content of 10% CuInS2 incorporated. The composite material of ZnO-RGO-10% CuInS2 can nearly completely degrade Rhodamine B (RhB) solution in 120 min, whereas bare ZnO itself can only degrade 20% RhB. The excellent photocatalytic performance of ZnO-RGO-CuInS2 demonstrates its promising in the photocatalytic or other extended applications. This work demonstrates a facile way to prepare integrative photosensitizer by taking advantage from the co-catalysts for more efficient and stable semiconductor based composite photocatalyst.

Annealing atmosphere strongly affects the structure of phosphorus-doped molybdenum carbide (P-Mo2C) nanodots hybridized with Ti3C2 MXene flakes and modulates its performance in the hydrogen evolution reaction. It is discovered that the nanohybrids undergo partial oxidation when they are annealed in N2, while retaining similar nanostructures when they are annealed in H2/Ar, Ar, and NH3. More importantly, compared with the nanohybrids annealed in Ar, NH3, and N2, the nanohybrid annealed in H2/Ar delivers the best HER performances, which delivers overpotentials (η10) of 172 and 219 mV at 10 mA cm−2, and Tafel slopes of 56.2 and 63.3 mV dec−1 in 0.5 M H2SO4 and 1.0 M KOH, respectively. The excellent HER performance could be attributed to optimal P-Mo2C nanodots for more accessible reactive sites, highly conductive Ti3C2 matrix for accelerated electron transfer, as well as N-doped carbon for more active centers. This work may shed light on developing the promising MXenes-based electrocatalysts by manipulating annealing atmosphere.

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.

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.

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.

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.

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.

Antimony selenide is a promising semiconductor with great application potential in the fields of optoelectronic devices. In this work, the vapor transport deposition (VTD) method is employed to prepare Sb2Se3 films on substrates. The influence of deposition temperature, distance between the Sb2Se3 sources and substrate, and the deposition holding time on the film morphology is investigated in detail. The deposited Sb2Se3 thin film is employed to fabricate photodetector with a structure of ITO/SnO2/Sb2Se3/Au, where the spin-coated SnO2 film is used as the buffer layer. The device demonstrates relative high responsivity in the range of 300–1000[Formula: see text]nm with a maximum value of 312[Formula: see text]mA W[Formula: see text] at 750[Formula: see text]nm.

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.

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...

TiO2 shell layer on the surface of ZnO nanowires (NWs) was synthesized by a layer by layer adsorption and reaction (LBLAR) method. Scanning electron microscopy image shows that the prepared ZnO–TiO2 core–shell NW arrays have a similar morphology with the well-aligned ZnO core NW arrays, providing the LBLAR cycles is controlled within a certain number. The prepared ZnO–TiO2 core–shell NW arrays were sensitized with CdS quantum dots to assemble quantum dots sensitized solar cells. Results indicate that a dramatic increase in open-circuit voltage and fill factor is achieved with an introduction of the TiO2 shell layer with a thickness of about 7 nm, resulting in a substantial improvement of the overall energy conversion efficiency. A rapid electron transfer from the CdS QDs to the ZnO NWs and a reduced electron recombination rate due to the energy barrier occurred at the interface between the ZnO core and the TiO2 shell are believed to contribute to the improved performance of the solar cells based on the ZnO–TiO2 core–shell NW arrays. In addition, effects of the TiO2 shell thickness on the performance of the as-fabricated devices are also discussed in detail.

Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs.

TiO 2 nanotube–nanoparticle mixture was prepared by a rapid anodization process in a perchlorate containing electrolyte followed by an ultrasonic process. Ag–TiO 2 nanocomposites were prepared at low temperature in polyethylene glycol (PEG600) solution, in which PEG600 was employed as the stabilizing agent as well as the reducer which can reduce Ag + on the surface of prepared TiO 2 nanocrystals. The synthesized samples were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray detector, X-ray photoelectron spectroscopy and UV–vis absorption spectroscopy. Results showed that well dispersed Ag nanoparticles with a typical size of 5–10 nm can be synthesized on the surface of TiO 2 nanocrystals assisted by the PEG600. To investigate the photocatalytic activity of the samples, TiO 2 powders with different Ag contents were prepared and employed to decompound methyl orange under UV-light irradiation. Compared with pure TiO 2 nanocrystals and commercial P25, a great improvement of photocatalytic performance was found for the Ag–TiO 2 nanocomposites. It is believed that the excellent photocatalytic properties of the samples prepared in our experiment mainly result from promoted separation of photogenerated electron-hole pairs and higher reductive power due to the formed heterostructure between TiO 2 and Ag as well as the advanced absorption of light due to surface plasmon effect of Ag nanoparticles.

ZnO microspheres sensitized by CuInSe2 and CuInS2 nanoparticles, which were synthesized by a solvothermal method and have a size about 20 and 3.5 nm, respectively, were used to a photodegradation of rhodamine B under an irradiation of mercury lamp. Results show that the photocatalytic activities of the ZnO/CuInSe2 and the ZnO/CuInS2 are much higher than that of the ZnO microspheres because of a formation of the heterojunction in two systems. It is also noted that the ZnO/CuInS2 exhibits a higher photocatalytic activity than the ZnO/CuInSe2, which is probably related to more suitable band gap to sunlight for CuInS2 nanocrystals and the larger specific surface due to a small size. Particularly, the ZnO/CuInSe2/CuInS2 shows the highest photocatalytic activities in all measured photocatalysts, which should be attributed to the formation of double heterojunctions among ZnO, CuInSe2, and CuInS2.

Ag–ZnO composite nanocrystals were prepared by a simple hydrolysis process of zinc acetate dihydrate together with a reduction of the Ag ions in diethylene glycol. Different contents of sodium hydroxide were added into the initial reaction mixture so as to form an effective contact between Ag and ZnO. X-ray diffraction analysis, ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterise the structural and morphological properties of the derived nanoparticles. The effects of the content of sodium hydroxide on the structural and morphological properties of the derived nanoparticles were discussed in detail. Photocatalytic measurement was also conducted, and the results indicate that the sample derived from 0·2M NaOH has the best ultraviolet photocatalytic activity for the degradation of the methyl orange aqueous solution among all the samples, which should be asc...

Copper indium selenide (CuInSe 2 ) nanocrystals with trigonal pyramidal shape are synthesized by a two-step process for photovoltaic applications. Structural, morphological and optical properties of the as-synthesized CuInSe 2 nanocrystals are characterized by using powder X-ray diffraction analysis, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–Vis absorption spectroscopy. Results indicate that the monodispersed nanocrystals show a single phase polycrystalline and the size of the trigonal pyramid is in the range of 10–12 nm, and the average composition ratio of the Cu/In/Se is measured to be 1.0:1.2:2.0. It is also investigated that the size and morphology of the CuInSe 2 nanocrystals can be tuned through a manipulation of the reaction time. Under an illumination of the simulated AM 1.5, the as-fabricated hybrid solar cell based on the P3HT/CuInSe 2 nanocrystals blends exhibits a promising open circuit voltage ( V oc ) of 0.42 V and its energy conversion efficiency is as 3 times as that of the solar cell fabricated by only the naked P3HT polymer.

Colloidal zinc sulfide (ZnS) quantum dots are synthesized by a solvothermal route from Zn(Ac) 2 ·2H 2 O, sulfur powder and oleylamine at 120–240 °C. Microstructural, morphological, and optical properties of the as-synthesized ZnS quantum dots are characterized by X-ray diffraction analysis, transmission electron microscopy, UV–vis absorption spectroscopy, and photoluminescence spectroscopy. Results indicate that the obtained ZnS quantum dots distribute uniformly, the particle size is in the range between 1.7 nm and 3.1 nm, and the band gap decreases from 4.16 eV to 3.90 eV with an increase of the particle size. The size-dependent photoluminescence exhibits a strongly broadened peak accompanied by a pronounced blue-shift. It is also found that the size of the ZnS nanocrystals can be effectively controlled by adjusting synthesis temperature. It is shown that the present method is also applicable to synthesize other binary II–VI semiconductor materials, such as ZnSe quantum dots.

In this paper, p-type CuInS2 quantum dots are synthesized by a solvothermal route and incorporated with n-type TiO2 nanoparticles by a thermal treatment process. Transmission electron microscopy (TEM) results indicate that the CuInS2 quantum dots distribute uniformly and the size is ∼3.4 nm. Photocatalytic activities of the TiO2 nanoparticles sensitized with the CuInS2 quantum dots are evaluated by the degradation of the methyl orange aqueous solution under ultraviolet (UV) and visible (vis) light irradiation and show an enhanced performance, compared with the pure TiO2 nanoparticles and the pure CuInS2 quantum dots. Microstructural, morphological, and optical properties of the TiO2 nanoparticles sensitized with the CuInS2 quantum dots are characterized by X-ray diffraction (XRD) analysis, TEM, and UV–vis absorption spectroscopy. Results indicate that the CuInS2 quantum dots greatly enhance the absorption of UV and visible light due to the p–n heterojunction being constructed between p-type CuInS2 quantum...

Vertically-aligned ZnO nanorod arrays on a fluorine-doped tin oxide glass substrate were homogeneously coated with visible light active CuInS2 quantum dots by using a controllable electrophoretic deposition strategy. Compared with the pure ZnO nanorod arrays, the formation of high-quality ZnO/CuInS2 heterojunction with well-matched band energy alignment expanded the light absorption from ultraviolet to visible region and facilitated efficient charge separation and transportation, thus yielding remarkable enhanced photoelectrochemical performance and photocatalytic activities for methyl orange and 4-chlorophenol degradation. The ZnO/CuInS2 film with the deposition duration of 80min showed the highest degradation rate and photocurrent density (0.95mA/cm(2)), which was almost 6.33 times higher than that of the pure ZnO nanorod arrays film. The CuInS2 QDs sensitized ZnO nanorod arrays film was proved to be a superior structure for photoelectrochemical and photocatalytic applications due to the optimized CuInS2 loading and well-maintained one-dimensional nanostructure.

Efficient carrier selective contacts and excellent surface passivation are essential for solar cells to reach high power conversion efficiencies. Exploring MoO x as a dopant-free, hole-selective contact in combination with an intrinsic hydrogenated amorphous silicon passivation layer between the oxide and the crystalline silicon absorber, we demonstrate a silicon hetero-junction solar cell with a high open-circuit voltage of 711 mV and a power conversion efficiency of 18.8%. Compared to the traditional p-type hydrogenated amorphous silicon emitter of a traditional silicon heterojunction solar cell, we observe a substantial gain in photocurrent of 1.9 mA/cm2 for MoO x due to its wide band gap of 3.3 eV. Our results on MoO x have important implications for other combinations of transition metal oxides and photovoltaic absorber materials.