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Organic pollutant is an environmentally harmful and ubiquitous aquatic pollutant with extensive production and application. In this study, a unique novel TiO2-based dual-sensitized heterojunction photocatalyst (PbS/CdS/TiO2) was successfully obtained by one step hydrothermal method, chemical bath deposition (CBD) method and ionic layer adsorption and reaction (SILAR) method. Scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive spectrometer characterized the composition. PbS/CdS was successfully decorated on the surface of TiO2 nanosheet array. As a stable catalyst with wide-spectrum (300–800 nm) optical response, excited electron–hole pairs of PbS/CdS/TiO2 could apply in degrading organic pollutants. Successfully, the degradation efficiency of PbS(5 C)/CdS(30 min)/TiO2 nanocomposites reached 99.9% under visible light, which was 5 times over pure TiO2. This ternary heterostructured materials will be well-promising photocatalysts.

A new strategy to enhance the photocatalytic properties of graphitic carbon nitride is reported via constructing an effective NiO decorated Ti/TiO2NT/TiO2/g-C3N4 S-scheme heterostructure photocatalyst thin film (Ti/TiO2NT/TiO2/g-C3N4/NiO). This thin film photocatalyst can separate hydrogen gas and oxygen gas into different sides of the Ti substrate. Owing to the synergistic effect of the NiO as co-catalyst and the formation of Step-scheme (S-scheme) heterojunction between g-C3N4 and TiO2, the electrons and holes were successfully separated to their opposing active centers, which is beneficial to inhibiting the recombination of the charge carriers. The gas evolution rate of Ti/TiO2NT/TiO2/g-C3N4/NiO is 7.97 μmol h−1 cm−2 under the irradiation of high-pressure mercury lamp, which was 3 and 1.3 times as high as that of the Ti/TiO2NT/g-C3N4 and Ti/TiO2NT/TiO2/g-C3N4, respectively. Firstly, benefiting from the well-matched band structure, a direct S-scheme Ti/TiO2NT/g-C3N4 heterojunction thin film is constructed easily driven by the built-in electric field across the Ti/TiO2NT/g-C3N4 interface. Furthermore, the introduction of the TiO2 layer on the TiO2NT will broaden light absorption range and increase the heterojunction area, which in turn conduces to effective charge separation. In addition, NiO as a co-catalyst cannot only accelerate the charge separation but also provide plentiful catalytic sites and decompose H2O2 produced by g-C3N4. The thin film photocatalysts can be recycled again, which is different from traditional powdered photocatalysts. This work constructs a NiO decorated Ti/TiO2NT/TiO2/g-C3N4 S-scheme heterostructure photocatalyst thin film, and provides a new insight to promote photocatalytic activity of g-C3N4 under the synergetic impact of S-scheme heterostructure and NiO co-catalyst. A novel NiO decorated Ti/TiO2NT/TiO2/g-C3N4 S-scheme heterostructure photocatalyst thin film was fabricated to enhance photocatalytic activity for water splitting.

Interfacial modification plays a vital role in boosting the performance of planar perovskite solar cells (PSCs). Here, perovskite-type BaTiO3 nanocrystals prepared by immersing dense blocking TiO2 (bl-TiO2) in Ba(NO3)2 solution were used as an interfacial modifier. The interface bonding was improved due to the fact that BaTiO3 and CH3NH3PbI3 (MAPbI3) have the same structure. Incorporation of BaTiO3 nanocrystals effectively boosted the electron extraction rate and suppressed the carrier recombination at the interface. The MAPbI3 grains nucleated and grew rapidly, resulting in larger grain size after introduction of BaTiO3 nanocrystals. Photoluminescence (PL) spectroscopy, time-resolved PL decay spectroscopy, and electrochemical impedance spectroscopy measurements verified that the BaTiO3 nanocrystals indeed promoted the carrier separation rate while suppressing nonradiative carrier recombination. By optimizing the bl-TiO2/MAPbI3 interface, the power conversion efficiency of planar PSCs based on bl-TiO2/BaTiO3 was improved from 15.03% to 17.71% [Jsc = 22.49 mA/cm2, Voc = 1.12 V, fill factor (FF) = 70%].

Anatase TiO2 nanocrystalline film prepared by using sol–gel method was assembled on TiO2 nanotubes to produce composite thin film photocatalyst and investigated as interfacial layer for the catalytic performance of Ti/TNT/N–P/NaTaO3:La (the nanostructures is Ti/TiO2 nanotubes/TiO2 nanocrystalline film/NiO film/NaTaO3:La) photocatalyst to generate hydrogen and oxygen under UV irradiation. The as-synthesized samples were characterized by FESEM, XRD, Element Mapping, UV–Vis, PL, I–V, and EIS. Characteristic analyses show that the interface between the TNT layer (TiO2 nanotubes) and P layer (NiO film) can be optimized by adjusting the number of N layers (TiO2 nanocrystalline film), thus affecting the efficiency of the photocatalyst. Compared with unformed TiO2 film, the Ti/TNT/N–P/NaTaO3:La photocatalyst with four TiO2 layers enhanced the H2 and O2 generation rate from 43.7 to 87.1 μmol/h which realized almost 2.0 times. The enhanced photocatalytic performance can be attributed to the low defect density and the effective separation of photo-generated electron–hole pairs. Furthermore, the performance stability of thin film photocatalyst was favorably showcased through multiple water splitting reactions, and the rational mechanism of improved photocatalytic property was interpreted systematically. In summary, such results have certain guiding effect on solving the weakness of composite film catalyst of interface defects and carrier recombination.

Electron transport layer plays a key role in improving charge extraction efficiency and inhibiting electron–hole recombination in perovskite solar cells. In this study, Ce ion was doped into compact TiO2 layer to improve electron transport performance of TiO2 thin film. Through UV–Vis and UPS tests, it was found that TiO2 obtained an appropriate band position after Ce ions doping. Specially speaking, Ce-doped TiO2 band position facilitates electron transport at the interface. As a result, the device based on 0.009 M Ce-TiO2 shows the power conversion efficiency is 16.18%, which is 5.75% higher than the device without Ce ions doping. In this work, we provided a new method to improve the electron extraction rate of TiO2 thin film, which is beneficial for performance of the devices.

Enhancement of integrity and stability of crystal lattice are highly challenging for polycrystalline perovskite films. In this work, a strategy of incorporation of nickel (Ni) ions is presented to modulate the crystal structure of the CH3NH3PbI3 perovskite film. A broad range of experimental characterizations reveal that the incorporation of Ni ions can substantially eliminate the intrinsic halide vacancy defects, since Ni ions have a strong preference for octahedral coordination with halide ions, resulting in significantly improved integrity and short-range order of crystal lattice. Moreover, it is also demonstrated that the stronger chemical bonding interaction between Ni ions and halide ions as well as organic group can improve the stability of the perovskite material. Simultaneously, the surface morphology of the perovskite thin film is also improved by the incorporation of nickel ions. As a result, a planar heterojunction perovskite solar cell incorporated with 1.5% Ni exhibits a power conversion efficiency of 18.82%, which is improved by 25% compared with 14.92% for the pristine device. Simultaneously, the device formed incorpration of 1.5% Ni shows remarkable stability with 90% of the initial efficiency after storage in an air environment for 800 h. The studies provide a new insight into metal-incorporated perovskite materials for various optoelectronic applications.

In this paper, we show that coating TiO2 with NaCl can simultaneously adjust the band gap of TiO2 layer and perovskite layer. The NaCl-coated TiO2 layer (0.2 mM/mL NaCl) exhibits better energy level match with perovskite layer than the uncoated samples. As a result, the NaCl-coated device exhibited a 15% improvement in power conversion efficiency (maximum value of 17.32%), with the open-circuit voltage improved from 1.01 V to 1.06 V.

The quality of perovskite film has great influence on photovoltaic performance of mesoscopic organic-inorganic halide perovskite solar cells, which is related to the mesoporous scaffold layers. In this paper, we present a modified two-step method to fabricate PbTiO3-decorated mesoporous scaffold layers for growing high-quality perovskite film, in which the mesoporous layers are treated by different concentration of Pb2+ solution. The introduction of moderate concentration of PbTiO3 is seen to promote the perovskite film growing and crystallizing, leading to reducing carrier recombination loss and defect density. The perovskite film based on treating concentration of 0.05 M exhibits larger size of crystal blocks, better quality of films, and higher surface coverage. Such a film applies in hole-counter-free perovskite solar cells with carbon-counter-electrode to obtain a power conversion efficiency of 10.55% along with a high open circuit voltage of 1.00 V. Moreover, these devices exhibit excellent long-term stability in an ambient atmosphere, which is related to the presence of the carbon electrode and PbTiO3.

As a cocatalyst, NiO has shown a great potential in facilitating photocatalytic water splitting for hydrogen evolution. In this work, a new photocatalyst thin film (Ni/NiO/NaTaO3: La) is successfully prepared to optimize the performance of the photocatalytic water splitting. The NiO cocatalyst is prepared by a simple heat treatment method. An efficient heterojunction can be formed between NiO and NaTaO3, which is beneficial to the transmission and separation of photogenic carriers. The photocatalytic activity of Ni/NiO/NaTaO3: La is 10.83 µmol/h cm2 under high-pressure mercury lamp irradiation, which is two times higher than that of Ni/NaTaO3: La. In addition, the Ni/NiO/NaTaO3: La thin film is treated under different temperatures. It can be observed that annealing temperature has a great influence on the photocatalytic activity of Ni/NiO/NaTaO3: La thin film. When the sample annealed in 700 °C, the photocatalytic activity for water splitting is the highest, indicating the temperatures have an effect on the formation of NiO and photocatalytic efficiency. Our photocatalyst thin film (Ni/NiO/NaTaO3: La) provides sustainable photocatalysts by taking both photocatalyst stability and repeated utilization into consideration. More importantly, this work also provides a new insight into the synthesis of Ni/NiO/NaTaO3: La thin film, which has a great application prospects in the field of photocatalytic water splitting. NiO cocatalyst is prepared by a simple heat treatment method and this novel photocatalyst thin film (Ni/NiO/NaTaO3: La) is successfully prepared to optimize the performance of the photocatalyst.

In this paper, we replaced mesoporous TiO2 nanoparticles scaffold layers by BaTiO3-coated TiO2 core–shell nanoparticles films which obtained by treating pure mesoporous TiO2 layers with 1.0 wt% barium nitrate solution, successfully realized the aim of optimizing interfaces bonding at TiO2/CH3NH3PbI3. Ultrathin BaTiO3 shell layer can combine better with CH3NH3PbI3 layer so as to reduce the existence of carrier recombination centers. Moreover, better optical absorption and larger fill factor were obtained in this manner by the reason of larger CH3NH3PbI3 grain size and fewer crystal boundaries. Furthermore, photoluminescence spectra and electrochemical impedance spectroscopy verified that our core–shell scaffold material contributes to accelerate carrier separation and retard carrier recombination. As a result, average power conversion efficiency enhanced from 11.20 to 13.76% under ambient conditions, which realized almost a quarter improvement than the devices based on pure mesoporous TiO2 layers. Such results have a certain guiding effect on solving interface defects and carrier recombination.

We adopt the dip-coating method using the viscosity of TiO2 sol to carry out the experiment aiming at combining both the advantage of morphologies of ordered and disordered nanostructures to select the photo-anode of TiO2. The nanoparticles scattering layer thin film growing at the TiO2 nanotubes (H:TTW) nozzle (H:TTWP) can increase the specific surface area of the top structure as well as can improve the adsorption of the quantum dots. Meanwhile, this nanostructure can keep the advantage of the direct electronic channel and the less vertical structure interface at the bottom of nanotubes. We use the method of successive ionic layer adsorption and reaction (SILAR) to conduct the quantum dot co-sensitization on the H:TTWP with CdS and Bi2S3. We found that the number of dip-coating with TiO2 nanoparticles was 6, it exhibited the best performance and reached a high photocurrent density of 9.34 mA/cm2, which is 2.1-times as many as Bi2S3/CdS/H:TTW system. What's more, the photoconversion efficiency is 6.13%. The improvement of the performance is mainly due to the enhancement of light absorption and the amount of heterojunctions of Bi2S3/CdS/TiO2, the ladder-like energy level structure and the novel morphology structure.

In the process of preparing CsPbBr3 films by two-step or multi-step methods, due to the low solubility of CsBr in organic solvents, the prepared perovskite films often have a large number of holes, which is definitely not conducive to the performance of CsPbBr3 perovskite solar cells (PSCs). In response to this problem, this article proposed a method of introducing InBr3 into the PbBr2 precursor to prepare a porous PbBr2 film to increase the reaction efficiency between CsBr and PbBr2 and achieve the purpose of In (Ⅲ) incorporation, which not only optimized the morphology of the produced CsPbBr3 film but also enhanced the charge extraction and transport capabilities, which was ascribed to the reduction of the trap state density and impurity phases in the perovskite films, improving the performance of CsPbBr3 PSCs. At the optimal InBr3 concentration of 0.21 M, the InBr3:CsPbBr3 perovskite solar cell exhibited a power conversion efficiency of 6.48%, which was significantly higher than that of the pristine device.

Herein, a novel actinomorphic flower-like ZnO/Au/CdS nanorods ternary composite photocatalyst is prepared to extend the light-responsive range, reduce the photogenerated charge carriers recombination, and ultimately improve the water splitting performance. Flower-like ZnO nanorods are synthesized by a chemical bath method and the CdS nanoparticles are sensitized by successive ionic layer adsorption and reaction method. Then the Au nanoparticles as co-catalysts are introduced by the photodeposition method to modify the interface of ZnO/CdS for reducing the photogenerated electron recombination rate and further improving the performance of water splitting. Detailed characterizations and measurements are employed to analyse the crystallinity, morphology, composition, and optical properties of the flower-like ZnO/Au/CdS nanorods samples. As a result, the flower-like ZnO/Au/CdS nanorod samples present significantly enhanced water splitting performance with a high gas evolution rate of 502.2 &mu, mol/g/h, which is about 22.5 and 1.5 times higher than that of the pure ZnO sample and ZnO/CdS sample. The results demonstrate that the flower-like ZnO/Au/CdS nanorods ternary composite materials have great application potential in photocatalytic water splitting for the hydrogen evolution field.

Actinomorphic flower-like SnO2 nanorods (NRs) were synthesized and then decorated by CuO nanoparticles (NPs) with diameter of 25 nm through a modified two-step process. The length and diameter of SnO2 NRs are about 0.4–1.8 μm and 60–200 nm, respectively. The gas-sensing testing results indicate that such unique CuO/SnO2 nanostructures exhibit an observably improved isopropanol sensing properties compared to the pure SnO2 NRs. The sensitivity of CuO/SnO2 sensor to 100 ppm isopropanol is 50.4, which is two time higher than that of the pure SnO2 sensor (22.1). The gas sensing mechanism may be related to p-CuO/n-SnO2 heterojunction formed at the interface of two oxides materials.

In this work, a TiO2 nanorods/nanoparticles hybrid arrays structure is used as the electron transporting layer in perovskite solar cells (PSCs). Compared with the devices based on bare TiO2 nanorods (NRs), the novel structure with rutile/anatase mixed phase can ensure a better growth of perovskite film and efficient separation of electron–hole. The device based on the nanorods/nanoparticles mixed phase structure shows the open-circuit voltage (Voc) of 0.96 V, short-circuit current density (Jsc) of 17.96 mA cm−2, fill factor of 0.61, yielding a power conversion efficiency (PCE) of 10.55% in ambient air under controlled humidity. The overall PCE enhancement of the device is 1.4 times higher than that of the bare NRs based PSCs. This study indicates that the nanorods/nanoparticles mixed phase structure has a great potential for application in PSCs.

Actinomorphic flower-like ZnO/ZnFe2O4 composite has been successfully synthesized by a facile two-step synthesis method. The as-prepared samples have been characterized by XRD, SEM and TEM. Compared with pure-ZnO sensor, the ZnO/ZnFe2O4-based sensor exhibited remarkably higher response, shorter response-recovery time and more superior selective to low-concentration NO2 at low operating temperature of 200 °C. The mechanism of enhanced gas-sensing performance of the ZnO/ZnFe2O4 composite with p-n heterostructure has been investigated. It indicates that the as-prepared ZnO/ZnFe2O4 composite is promising for NO2 gas sensor.

The hole-transporting materials and noble metal employed in normal perovskite solar cells (PSCs) limited their practical application. In this work, the high photovoltaic performance hole-conductor-free PSCs based on carbon counter electrode were fabricated in air atmosphere with high humidity condition (HR) around 55%. An efficient TiO2 blocking layers (BL-TiO2) was prepared by spin-coating the precursor solutions containing ethanol (CH3CH2OH), titanium n-butoxide (Ti(OC4H9)4) and diethanolamine (C4H11NO2 DEA) with different molar ratios (CH3CH2OH: Ti(OC4H9)4: DEA = 30: 1: x) on TiCl4 per-treated FTO glass. When adding DEA in Ti precursor solution, it would revamp the cracks of blocking layer, the suitable alkaline environment provided by DEA can contribute to growing compact BL-TiO2. Electrical impedance measurements were performed to investigate the kinetic issues of charging transport performance in PSCs with different amount of DEA. The optimized PSCs exhibited a short-circuit photocurrent density of 22.71 mA/cm2, open-circuit voltage of 954 mV, fill factor of 0.55 and power conversion efficiency (PCE) of 11.92% when DEA molar ratios x = 0.75. The PCE of optimized PSCs retained about 90% after 21 days in air with HR around 55%. The low cost and outstanding properties endow the present carbon counter electrode based PSCs with immense application potentials.

In this work, high stable perovskite solar cells (PSCs) based carbon counter electrode were fabricated in the air environment with 30% of humidity, in which the perovskite CH3NH3Pb(I1-xBrx)3 were used as the absorber. We investigated the effect of the different Br-doping (x = 0.00, 0.10, 0.15, 0.20, 0.25, 0.30) on the devices performance and found that the appropriate amount of Br-doping could effectively improve crystallinity of the perovskite film and enhance the light absorption. When the doping-ration x was 0.25, the device exhibited the best performance with the efficiency of 9.99% with active area of 0.2 cm2 under the irradiation of 100 mW/cm2 air mass 1.5 global (AM1.5G) sunlight. By electrochemical impedance spectroscopy (EIS) measurement, we found that the introducing of Br− into the perovskite film could reduce the carrier recombination loss. Finally, the stability test of the PSCs was carried out and the result showed that the device still keep 96.23% of the initial efficiency after being stored in the air for 56 days (1344 h), which show an excellent stability.

A uniform and compact CdTe thin film is successfully electrodeposited on Ni flexible sheets. The influence of the concentration of sodium citrate in the growth solution on the morphological, compositional and electrical conductive properties of CdTe films is investigated. The results show that sodium citrate plays a significant role in directing the morphological evolution of CdTe from three-dimensional rod-shaped array to two-dimensional thin film. The composition of the film is changed from Te-rich to Cd-rich, and the conversion from p-type conduction to n-type in CdTe films is also achieved with the increase of sodium citrate concentration. When the concentration of sodium citrate is 0.08 mol L−1, the composition of CdTe film is near stoichiometric and the amount of excess Te is small. Furthermore, the effect of sodium citrate on the photoelectric conversion properties of CdTe-based solar cells is also analyzed. The fabricated solar cell based on the CdTe film prepared using 0.08 mol L−1 sodium citrate shows a short-circuit current density of 10.46 mA cm−2 and an open-circuit voltage of 0.53 V, yielding a better energy conversion efficiency of 2.73% with a fill factor of 49.28%. The better energy conversion efficiency is 2.1 and 1.6 times higher than that of the devices based on CdTe films prepared using 0.07 and 0.09 mol L−1 sodium citrate, respectively. This study indicates that the as-prepared CdTe thin film has a great potential for application in thin film solar cells, and the sodium citrate-assisted synthesis of CdTe film suggests a promising technique for large-scale fabrication of flexible solar cells.

Doping, interface optimization and recrystallization are effective approaches for fabricating high performance perovskite solar cells (PSCs). In our work, simple CsBr treatment is introduced to improve the performance of TiO2 nanorods-based PSCs. Both Cs+ and Br− are doped into CH3NH3PbI3 simultaneously, as well as optimizes the interface between perovskite and hole-transporting material (HTM). In addition, the perovskite grains are recrystallized through this method. Finally, a power conversion efficiency (PCE) of 16.02% with 0.72 in fill factor (FF) and 1.08 in open circuit voltage (VOC) is obtained through CsBr treatment, which is 19.91% higher than that of untreated devices (13.36% with 0.65 in FF and 1.02 in VOC). Furthermore, the power output maintains ∼14% after 3500 h under the humidity within 15% at room temperature.

This paper reports a newly developed two-step method for the synthesis of a unique nanocomposites consisting of inner spherical-coral-like SnO2 nanorods (NRs) (lengths of 0.4–1.8 μm and diameters of 60–200 nm) decorated by out α-Fe2O3 nanocrystallites (NCs) with an average grain size of ～20 nm. The introduction of α-Fe2O3 NCs on the surface of SnO2 NRs promotes the formation of heterojunction barrier at the interface of the two oxides. The gas-sensing results show that the sensor based on α-Fe2O3-decorated SnO2 NRs exhibit outstanding sensitivity, selectivity, and stability to ethanol vapor at a low optimum work temperature of 280 °C. In particular, a higher response can be obtained, by contrast, than that of pure SnO2 NRs along with greater response-recovery capacity. The significant improvement of ethanol sensing behavior may be attributed to the chemical and electronic sensibilization induced by the α-Fe2O3 NCs.

In this work, organic-inorganic hybrid perovskite solar cells (PSCs) were fabricated under air atmosphere with high humidity condition around 55%. A modified method was demonstrated for forming the TiO2 blocking layers (BL-TiO2) with various thickness by spin-coating the mixed precursor solutions of ethanol (CH3CH2OH), diethanolamine (DEA) and titanium n-butoxide (Ti(OC4H9)4) with different volume ratios (CH3CH2OH: DEA: Ti(OC4H9)4 = 24: 1: R). The thickness of BL-TiO2 increased from 16 to 54 nm with a rise of R from 1.5 to 4.0. We demonstrated that suitable thickness of BL-TiO2 was beneficial to enhancing the photovoltaic performance of PSCs. The kinetic parameter of electron transport was investigated by the electrical impedance measurements, and then the influence of BL-TiO2 thickness on electron transport performance in PSCs was further discussed. The optimized PSCs delivered a short-circuit photocurrent density (JSC) of 20.61 mA/cm3, open-circuit voltage (Voc) of 939.4 mV, fill factor of (FF) of 0.661 and overall conversion efficiency (η) of 12.80% when the thickness of BL-TiO2 was about 31 nm (R = 2.4). The photovoltaic performance of mesoporous PSCs was extremely dependent on the thickness and morphology of blocking layer.

In this work, hole-conductor-free mixed organic cation perovskite solar cells based on carbon counter electrode were fabricated under air atmosphere with high humidity condition around 50%. The photovoltaic performance of the perovskite solar cells with mixed organic cation perovskite (FA)x(MA)1−xPbI3 by chemical modification the molar ratios x were demonstrated. The light harvesting abilities and crystal morphology could be controlled with x from 0 to 0.4 which resulted in a corresponding diversification of photoelectric properties in perovskite solar cells. Electrical impedance measurements were performed for investigating the electron transport issues in perovskite solar cells with various x. The optimized perovskite solar cells delivered a short-circuit photocurrent density of 21.63 mA/cm3, open-circuit voltage of 980 mV, fill factor of 0.45 and overall conversion efficiency of 9.53% as x = 0.3. The long-term stability of the optimized perovskite solar cells was exhibited and the overall conversion efficiency retained about 91% after 49 days in air with humidity around 50%. The hole-conductor-free perovskite solar cells based on carbon counter electrode have low-cost and bring a prosperous application foreground in the future photovoltaic community.

In this study, vertically aligned titanium dioxide nanosheets (TiO2NSs) array films were employed for the fabrication of photoanodes for quantum-dot sensitized solar cells (QDSSCs). The TiO2NSs array films were synthesized by a hydrothermal method. Then, cadmium sulfide (CdS) and cadmium selenide (CdSe) were assembled onto the TiO2NSs array films through chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR), respectively. Detailed characterization measurements were carried out to analyse the crystallinity, microstructure, composition and optical properties of the samples. The CdS and CdSe QDs were densely and uniformly deposited on both {001} and {101} facets of the TiO2NSs array films. Moreover, the effect of CdS deposition time and number of CdSe deposition cycles (C) on the photoelectric performance was also investigated in detail. The best performance of 4.77% was achieved under AM 1.5 G illumination with Jsc = 18.22 mA cm−2, Voc = 0.51 V, and FF = 0.52 when the deposition time of CdS was 30 min and the deposition cycle of CdSe was 10C. The enhanced photoelectric performance mechanism of the co-sensitized device is also discussed in this paper.

Highly reproducible and enhanced-efficiency perovskite solar cells based on oriented 1D TiO2 have been successfully fabricated from DMF/DMSO mixed solvents by a simple one-step deposition method, and the whole experimental section was proceeded in the air with temperature of 25–35 °C and humidity of 40–60% without a glove box. We have specifically studied the proportion of the DMF/DMSO mixed solvents influenced on the preparation of perovskite films and the efficiency of perovskite solar cells. Another main emphasis of our work was focus on the reproducibility of the perovskite solar cells, 40 fully independent devices for each kind of solar cells have been statistically analyzed, and the main photovoltaic parameters with small standard deviation (less than 0.6 of J sc and PCE, less than 0.03 of V oc and FF) indicating that the devices have excellent reproducibility. The best-performing device fabricated from 50 wt% DMF/DMSO mixed solvents showed the average efficiency as high as 10.56% with negligible hysteresis phenomenon, which was over 95% higher than those from pure solvents. These results may provide helpful progress toward the understanding of the function of the solvents for preparing extremely high-quality perovskite films and high-reproducible perovskite solar cells in ambient air.

In this study, a uniform CdTe nanorods (NRs) arrays are grown on Ni substrates by a simple one-step electrochemical deposition method. The effects of deposition parameters such as the concentration of reactants and reaction time on the growth of CdTe NRs arrays are systematically investigated. Na2TeO3 and CdSO4 have a significantly different influence on the growth of CdTe NRs. With the increase of Na2TeO3 concentration, the diffraction intensity increases slightly at the peak (111) to promote axial growth. The diffraction intensity of (002) can increase with the concentration of CdSO4 increasing, which is conducive to lateral growth. The morphology of CdTe film varies from a thin layer to nanoparticles, and finally to NRs with the extension of time. Based on the characterization results, the possible growth mechanism of CdTe NRs arrays is proposed. The as-prepared CdTe NRs arrays are then embedded into CdS film, forming a novel three-dimensional (3D) heterojunction photovoltaic device. An extensive study of the effect of NRs length on device performance is presented. The results indicate that the device performance is highly dependent on the length of CdTe NRs, and a power conversion efficiency of 2.50% is obtained for optimal length of 1 μm. The better photovoltaic performance can be attributed to its efficient charge separation and direct pathways for carriers transport. What's more, this novel 3D nanostructured concept suggests great potential for other optoelectronic devices.

High visible light photocatalytic activity of N-doped TiO 2 (N-TiO 2 ) photocatalysts were prepared by facile sol-gel method in large-scale without separation, purification and thermal treatment at high temperature. Ammonium nitrate (AN) was used as nitrogen source and solid substrates, hydrous TiO 2 deposited onto the surface of AN micro-particles during the formation of compound gel. AN thermal decomposed and N-TiO 2 photocatalysts were obtained by compound dry gel (CDG) calcined at low temperature. N element thermal diffused enter into lattice of TiO 2 , and the effects of AN evidently facilitated the product transformation from amorphous to anatase. Meanwhile, the doped N element promoted the formation of doping level and its light absorption edge extended to visible region. We systematically research the doping ratio of AN, the different calcined time at low temperature to prepare N-TiO 2 with high photocatalytic activity in visible region. As-prepared N-TiO 2 photocatalysts exhibited excellent photocatalytic activity under the illumination of visible light, and the photodegradation reaction rate constant was approximately 6 times higher than pure TiO 2 samples.

Herein, we report an ionic cross-linkage process of synthesizing [001] preferred oriented anatase TiO2 nanowires and nanotubes hybrid structure (TWTs) based on anodization method wherein varied amounts of TiF6 2− ions are added in synthetic process. We show how the TiF6 2− ions switch the growth direction of TWTs from [101] to [001] (denoted as T101WTs and T001WTs, respectively) and change their geometrical morphologies, i.e., small ionic radii TiF6 2− ions migrate and partly replace the TiO6 2− octahedra under electric field, which separate out and leave vacancies during annealing process, resulting in a reconstruction of TiO2. Importantly, absorption property and photoelectrochemical (PEC) performance of T001WTs exceed those of T101WTs. Furthermore, CdS QDs are assembled onto TWTs photoelectrodes by successive ionic layer adsorption and reaction technique. Likewise, T001WT/CdS presents superior absorption capability and enhanced PEC performance to those of T101WT/CdS. This could be attributed to their preponderances of improved light absorption capability and decreased electron recombination.

Vertically aligned CdTe nanorods (NRs) arrays are successfully grown by a simple one-step and template-free electrodeposition method, and then embedded in the CdS window layer to form a novel three-dimensional (3D) heterostructure on flexible substrates. The parameters of electrodeposition such as deposition potential and pH of the solution are varied to analyze their important role in the formation of high quality CdTe NRs arrays. The photovoltaic conversion efficiency of the solar cell based on the 3D heterojunction structure is studied in detail. In comparison with the standard planar heterojunction solar cell, the 3D heterojunction solar cell exhibits better photovoltaic performance, which can be attributed to its enhanced optical absorption ability, increased heterojunction area and improved charge carrier transport. The better photoelectric property of the 3D heterojunction solar cell suggests great application potential in thin film solar cells, and the simple electrodeposition process represents a promising technique for large-scale fabrication of other nanostructured solar energy conversion devices.

The hierarchical ZnO nanostructures with 2-fold symmetrical nanorod arrays on zinc aluminum carbonate (ZnAl-CO3) nanosheets have been successfully synthesized through a two-step hydrothermal process. The primary nanosheets, which serve as the lattice-matched substrate for the self-assembly nanorod arrays at the second-step of the hydrothermal route, have been synthesized by using a template of anodic aluminum oxide (AAO). The as-prepared samples were characterized by XRD, FESEM, TEM and SAED. The nanorods have a diameter of about 100 nm and a length of about 2 μm. A growth mechanism was proposed according to the experimental results. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to ethanol at 230°C. In addition, the response mechanism of the sensors has also been discussed according to the transient response of the gas sensors.

This paper reports a facile two-step synthesis route for the preparation of flower-like ZnO/α-Fe 2 O 3 nanorods (NRs). Flower-like ZnO NRs with the average diameter about 810 nm and length about 4.5 µm were firstly synthesized via a chemical solution method, and then ZnO NRs was coated with a continuous α-Fe 2 O 3 layer to form ZnO/α-Fe 2 O 3 core-shell structure through an ionic-layer adsorption and reaction method. The gas-sensing results show that the ZnO/α-Fe 2 O 3 NRs exhibit excellent sensitivity, selectivity, and response-recovery capacity to ethanol vapor at a low optimum temperature of 240 °C. In particular, compared with pure ZnO NRs and α-Fe 2 O 3 nanoparticles (NPs), the ZnO/α-Fe 2 O 3 NRs show an obvious improvement in gas sensing properties. The substantial improvement of sensing properties may be attributed to the unique microstructure and heterojunction formed between ZnO and α-Fe 2 O 3 .

In this study, a uniform and dense cadmium sulfide (CdS) thin film is utilised as an electron-transport layer in CH3NH3PbI3-based perovskite solar cells (PSCs). CdS films are synthesized by a homogeneous precipitation method in urea aqueous solution. The effect of urea concentration on the growth of CdS films has been investigated. It is noted that increasing urea concentration remarkably affects the grain size and uniformity of the films. A compact CdS thin film with appropriate grain size can be obtained by adding 1.5 M urea. The photovoltaic performance of the PSCs based on the as-prepared CdS films is also studied. The photovoltaic conversion efficiency (PCE) of the PSCs shows a significant dependence on CdS layers. The highest PCE is obtained by using a CdS thin film prepared in 1.5 M urea, which can be attributed to the better coverage of perovskite on the CdS film for efficient charge separation and transport.

In this study, we report a TiO2 hybrid structure prepared by a facile route, wherein TiF62− ion has been used as both the surfactant and titanium source. Single-crystalline TiO2 nano-polyhedrons with exposed high active {001} facets were grown on a TiO2 nanowire and nanotube (TWTs) films. This hybrid structure served as a model architecture for efficient photoelectrochemical (PEC) devices because it simultaneously offered a large contact area with the electrolyte and direct pathway for photoexcited electron collection. Under simulated sunlight illumination (AM 1.5 light at 100 mW cm−2), this hybrid structure exhibited a photocurrent density of 1.36 mA cm−2 at 0 V vs. Ag/AgCl (JSC) and photoconversion efficiency (η) of 0.81% at −0.51 V vs. Ag/AgCl, nearly 2.4 times higher than those of the bare TWTs. Morphology of the TiO2 nano-polyhedrons in the hybrid structure was greatly influenced by the TiF62− ion concentration, and a proper concentration was determined to be 2.5 mM. Moreover, the CdS QDs were sensitized onto the hybrid structure, and their JSC and η reached 2.31 mA cm−2 & 1.94%, respectively, 1.5 times higher than those of the CdS-sensitized bare TWTs. The TiO2 nano-polyhedrons improved the efficiency via increasing the specific surface area of the electrode, thus facilitating hole transfer into the electrolyte. Moreover, the exposed high reactive {001} facets provided more effective area for the adsorption of CdS, leading to an enhanced photogeneration carrier density.

High performance perovskite light harvester layer on the TiO2 nanorods array is firstly prepared by an acetic acid vapor-assisted thermal annealing (HAc VATA) method. The crystallinity of CH3NH3PbI3 layer is improved through introducing HAc vapor. Furthermore, the pore filling fraction of TiO2 nanorods array is increased and the contact between TiO2 and CH3NH3PbI3 is enhanced. As a result, the HAc VATA devices exhibit an average PCE of 12.20%, which is 63.54% higher than that of the usual thermal annealing devices (7.46%).

In this paper, a new thin film photocatalysts of Ti/TNT/N-I-P/NaTaO 3 (the nanostructures is Ti/TiO 2 /TiO 2 -PbS-NiO/NaTaO 3 ) is designed for photocatalytic water splitting. This photocatalysts can separate the evolution gas of H 2 and O 2 into the different sides of the Ti substrate. It is because that the p-i-n junction can separate and transport the photogenerated electrons and holes to their opposing reaction centers. Moreover, these thin film photocatalysts can be recycled again. Which is different from traditional powdered photocatalysts. The photocatalytic activities for water splitting show that the amounts of evolved gas of Ti/TNT/N-I-P/NaTaO 3 is 8.73 μmol/h cm 2 under high-pressure mercury lamp illuminations, which is 7 times higher than that of Ti/NaTaO 3 thin film photocatalysts. Two aspects can contribute to this performance: the one is the structure of N-I-P/NaTaO 3 ; the other one is electrical conduction layer TNT. This study provides a new insight into synthesis of thin film photocatalysts to liberate H 2 and O 2 separately from H 2 O.

Hierarchical rutile/anatase TiO 2 heterogeneous film for photoelectrochemical application is reported in the work. The TiO 2 heterogeneous film is fabricated by two-step hydrothermal method and possesses high light harvesting property. The heterojunction formed at the interface between anatase and rutile facilitates photogenerated charge carrier separation, resulting in reduced electron recombination with holes in the electrolyte. The optimal photocurrent density of bare TiO 2 heterogeneous film was 0.90 mA/cm 2 at a potential of 0 V versus Ag/AgCl. In addition, the TiO 2 heterogeneous film offers a large surface area for quantum dots anchoring and exhibits a significant improvement in photoelectrochemical performance. The photocurrent density of PbS/CdS co-sensitized TiO 2 heterogeneous film was enhanced to 7.72 mA/cm 2 . The results indicate that the designed TiO 2 heterogeneous structure possesses superior charge separation efficiency and photoelectrochemical properties.

Flower-like CuO/ZnO hierarchical structures were prepared via a flexible two-step synthesis method, in which nanorods-assembled flower-like ZnO microstructures with the diameter about 430–1680 nm and the length about 3.6–8.8 μm were prepared in advance through a chemical solution method, and then a frost-like layer of CuO nanoparticles (NPs) decorated on the surface of ZnO nanorods (NRs) via an ionic-layer adsorption and reaction method. Compared with pure ZnO NRs, the flower-like CuO-decorated ZnO NRs show an obvious improvement in gas sensing performance. The gas sensing mechanism of the CuO-decorated ZnO NRs was discussed in relation to the catalytic effect of CuO and the introduction of the p-n junction between CuO and ZnO.

The cadmium sulfide (CdS) film is deposited on the surface of cadmium telluride (CdTe) nanorods (NRs) by two different methods, successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) techniques. The influence of the deposition parameters on the properties of the films is investigated. Compared to SILAR, CBD is a simple and time saving technique, which can ensure full coverage and better growth of CdS on the surface of CdTe NRs. The photovoltaic characteristics of CdS sensitized CdTe films are also investigated. It is found that the CdTe/CBD-CdS thin film demonstrates excellent photoelectrical properties, which is ascribed to the large absorption coefficient of the material, indicating the potential applications in solar cells.

Hierarchical porous SnO 2 (HP-SnO 2 ) nanoparticles (NPs) were synthesized via a modified sol-gel method by employing polystyrene (PS) microspheres as a template and SnCl 2 as a tin source. The samples presented a three-dimensional random arrangement of macropores with average pore diameter of about 210 nm, of which the pores walls were composed of NPs with the size of about 11 nm. The N 2 -sorption analysis showed that the presence of the hierarchical mesoporous structure in the samples. The gas-sensing measurements showed that the response of HP-SnO 2 based sensor reached the maximum value at the operating temperature of 240 °C, which was 60 °C lower than that of SnO 2 based sensor. Moreover, the HP-SnO 2 exhibited a significant improvement for the response and a short response-recovery time to ethanol vapor. The results indicated that HP-SnO 2 NPs were of great potential for application in ethanol sensors.

A novel cage-like CdTe film with even porosity size and good connectivity among particles is successfully prepared by a simple technique for the first time. The field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and UV-Vis absorption spectra are used to characterize the morphology, crystallinity and optical property of the new structure. The FESEM observation confirms the formation of cage-like CdTe film after heat treatment. The structural and optical studies reveal that the cage-like CdTe films show better crystallinity and enhanced optical absorption. Based on the characterization results, the possible growth mechanism of the cage-like CdTe film is proposed. Furthermore, the photoelectrochemical property of the film is also investigated by photocurrent and current density–voltage curves and electrochemical impedance spectroscopy (EIS). The cage-like CdTe film yields an enhanced photocurrent and current density of 3.8 mA cm−2, which is significantly higher than other as-prepared CdTe films. Meanwhile, the cage-like CdTe films present improved charge transfer properties and corroborate the photocurrent and current density–voltage measurements. The photostability of the films is also studied. The better photoelectrochemical property of the cage-like CdTe films suggests their potential application in nanostructured solar energy conversion devices.

The ability to control the exposure of facets of a crystal has been garnering considerable attention due to the fascinating dependence of the physical properties of crystals on their shapes. Herein, a TiO2WT photoelectrode decorated with anatase TiO2 nanocuboids (TiO2C111WTs) displaying high-energy exposed (111) facets and quantum dot dimensions was prepared for the first time by using a TiCl4 treatment process. F− and NH4+ were introduced together to limit the randomness of the TiCl4 hydrolysates. We propose that both F− and NH4+ were necessary for controlling the exposure of the (111) facets. In comparison with TiO2WT photoelectrodes decorated with either randomly deposited TiO2 nanoparticles (non-facet) or with TiO2 nanofilms or with TiO2 nanocuboids displaying exposed {001} facets (denoted as TiO2PWT, TiO2FWT and TiO2C001WT photoelectrodes, respectively), the hybrid-structured TiO2C111WT photoelectrode achieved superior PEC performances, with Jsc and photoconversion efficiency values of 0.97 mA cm−2 and 0.49%. This enhancement was attributed to the exposure of the highly active (111) facets and the increased specific surface area of TiO2C111WTs. Meanwhile, the photoactive (111) facets offered oxygen vacancies, resulting in an increase of donor density and the enhancement of PEC performances. These facets also promoted the adsorption of CdS QDs and hence further sensitization. The CdS/TiO2C111WTs achieved Jsc and photoconversion efficiency values of 3.95 mA cm−2 and 2.05%, which were about twice those of CdS/TiO2WTs.

Without templates and any addition of surfactants, cadmium telluride (CdTe) microstructures with various novel morphologies were fabricated by one-step electrodeposition in the acid system during the deposition potential range from −0.65 V to −0.50 V (vs. Ag/AgCl). The structures and properties of the as-synthesized films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis absorption spectroscopy and photoelectrochemical measurements. XRD pattern revealed that the high-purity CdTe films were cubic phase and exhibited the preferential orientation along (1 1 1) direction. The SEM indicated that by varying the deposition potential, we can obtain CdTe structure arrays with different morphologies evolution from microrod arrays to highly ordered flower-like structures. In addition, based on the better optical and photoelectrochemical performances, these CdTe microstructures would be potentially applied for substrate configuration photovoltaic device applications.

In this work, CsPbBr3/TiO2 nanocomposite photocatalyst exhibiting high visible light photocatalytic activity has been fabricated via a facile solution synthesis route at low temperature. CsPbBr3 quantum dots (QDs) were prepared by using supersaturated recrystallization method, and the surface was coated with amorphous TiO2 to enhance its stability. The CsPbBr3/TiO2 photocatalyst had excellent light absorption performance in a broad wavelength range and strong adsorption capacity for the organic pollutant. The formation of heterojunction between CsPbBr3 and TiO2 promoted the charge separation and thus improved the photocatalytic activity. In addition, photocatalytic degradation tests showed that the as-prepared nanocomposite exhibited high visible-light-induced photocatalytic activity under the simulated sunlight irradiation. And the obtained composite had long-term stability in water system and potential practical application value in the field of environmental governance.

The quality of the photoactive layer gravely affects the characteristics and stabilities of photovoltaic device. Here, by introducing polyethylene glycol (PEG) into the methylammonium lead trihalide (MAPbI3) precursor solution, we fabricate high-quality MAPbI3 perovskite film with high coverage and large grain size. By adjusting the PEG concentration into the perovskite film, the hole-conductor-free mesoporous perovskite solar cell with carbon electrode exhibits a boosted power conversion efficiency of 11.62%, which originates primarily from the enhancements of light absorption and acceleration of carriers transfer. Meanwhile, hygroscopic PEG protects the perovskite film from moisture, which leads to the perovskite film and corresponding device exhibit superior stability. This work confirms a high-efficiency and feasible strategy using polymer materials to enhance the performance in power conversion efficiency and stability of perovskite solar cells.