Double-layer ZnO Research Articles

Electrophoretic deposition of double-layer ZnO porous films for DSSC photoanode

Electrophoretic deposition of double-layer ZnO porous films for DSSC photoanode

Antireflection and photocatalytic single layer and double layer ZnO and ZnO–TiO2 thin films

Due to climate change and the need to use renewable energy resources, solar cell modification is being considered by scientists around the world. Photocatalytic and anti-reflective coatings on solar cells can affect the efficiency and stability of solar cells. In this study, single-layer zinc oxide thin films and double-layer ZnO–TiO2 thin films were investigated to study their photocatalytic and optical properties. In fact, the effect of porosity and the application of double-layer thin films on the optical and photocatalytic properties of coated glass were studied. Mesoporous thin films thinner than 100 nm were synthesized using a sol-gel process and the ZnO thin film with 2 × 10-2 M pore-forming agent (CTAB) in the coating solution had the highest transparency and ultraviolet absorption, and the ZnO thin film with 4 × 10-2 M pore-forming agent had the best antireflection performance. The double-layer thin film consisted of dense (interlayer) and mesoporous (top layer) ZnO layers had the best anti-reflection performance. It reduced the reflection of the glass substrate by 2.05%. Investigation of the effect of the coating thickness on optical properties showed that higher film thickness can lead to a shift of the visible wavelength with the highest transparency such that the increase of withdrawal speed from 1 mm/s to 5 mm/s resulted in an increase of this wavelength from 530 nm to 590 nm. The photocatalytic studies of the ZnO double-layer coatings showed that 120 min of ultraviolet irradiation could completely recover the transparency of the samples contaminated with fatty acid.

PHOTOCATALYTIC DEGRADATION OF RHODAMINE B UNDER UV USING DOUBLE-LAYER ZnO: Fe THIN FILM

Waste dyes are a major source of water pollution, which is a critical environmental issue. The purpose of this study is to synthesize double-layer ZnO: Fe 5-20% thin films and investigate the degradation of rhodamine B in these films. The creation of the ZnO phase with the wurtzite hexagonal structure may be seen in the thin film X-ray diffraction pattern. Only marginally lessened energy bandgap (3.11-3.09 eV), optical transmission spectra, and lattice strain was seen after Fe was added to ZnO thin films. With increasing Fe concentration, it was found that the hydrophilicity and photocatalytic characteristics of ZnO thin films considerably decreased, as shown by the contact angle going from 51.4 to 70.71 and the decomposition efficiency going from 61.46% to 50.35%. The double-layer ZnO layer's optical characteristics diminish as the Fe concentration rises.

Applicability of anti-corrosion for slippery liquid-infused porous surface using a double-layer ZnO nanostructure on Al foil

Applicability of anti-corrosion for slippery liquid-infused porous surface using a double-layer ZnO nanostructure on Al foil

Performance enhanced Metal‐Semiconductor‐Metal photodetector based on double‐layer ZnO nanorods

This study reports that photodetectors based on double-layer ZnO nanorods grown on AZO seed layer by hydrothermal method. Compared with the photodetectors with single-layer nanorods, the on/off ratio of the photodetectors with double-layer ZnO nanorods is increased by ∼2.52 times, the photoresponsivity is increased ∼5.50 times, the sensitivity is increased ∼3.34 times and the response time was shortened by 0.97 and 6.65 s, respectively. Furthermore, the photocurrent derivative also shows that the photodetectors based on double-layer ZnO nanorods has a faster response speed.

Effect of concentration double layer ZnO/ZnO:Ag on optical and photocatalytic properties

ZnO is a semiconductor material that advantages in various applications, especially for photocatalysts. The catalytic activity of ZnO is much better than other materials, because ZnO can absorb light in a wider spectrum. The double layer ZnO/ZnO:Ag with various concentrations of 0.1 M, 0.3 M, and 0.5 M has been successful deposition. Double layer ZnO/ZnO:Ag deposition was carried out by sol-gel method and spray coating deposition technique. The results showed that the concentration of double layer ZnO/ZnO: Ag increased with the increase of the absorbance value. From the transmittance spectrum attempt was made to estimate the value of energy band gap of the samples. Double layer ZnO / ZnO:Ag energy gap in the range 3,2-3,3 eV. The energy gap of Double Layer ZnO/ZnO:Ag decreases with increasing concentration to 0.5 M. Double layer ZnO/ZnO: Ag 0.5 M has the smallest energy gap of 3.21 eV. Photodegradation testing was carried out to determine the ability of samples to photocatalytic activity at methylene blue dye. The optimum photocatalytic activity is indicated by the largest percentage of degradation. The largest percentage of degradation was shown by Double layer ZnO/ZnO:Ag 0.3 M at 81.5%.

Facile sputtering enables double-layered ZnO electron transport layer for PbS quantum dot solar cells

PbS colloidal quantum dot solar cells (CQDSCs) employ ZnO electron transport layer have achieved high efficiency. However, there is nearly no efficient and batch production method to balance the charge separation and recombination within the device, which is one of the most obviously barrier to a satisfactory conversion efficiency. Here, a n+-n double-layered ZnO electron transport layer (DETL) is prepared by a facile one-step magnetron sputtering under different Ar pressure, and employed in heterojunction PbS colloidal quantum dot solar cells (CQDSCs) for the purpose of increasing charge separation at heterojunction interface via energy-band alignment modulation. The ZnO DETL, composed of a 100-nm-thick n+-ZnO bottom layer (n = 8 × 1019 cm−3) and a 20-nm-thick n-ZnO top layer (n = 3 × 1016 cm−3) significantly improve the power conversion efficiency (PCE) of the CQDSCs by a factor of ~35% compared to the device with single-layered n- ZnO. Open-circuit photovoltage decay (OCVD) measurements prove that the graded energy alignment of ZnO DETL effectively reduces both interfacial and trapping-assisted charge recombination, relative to the single-layered ZnO. The facile Ar-pressure tuning method makes the energy-band alignment process more convenient and sheds a light on the application of DETL electrons transport layer, fabricated by the universal technique of magnetron sputtering.

Lubricant-infused coating by double-layer ZnO on aluminium and its anti-corrosion performance

In this study, double-layer zinc oxide was synthesized on an aluminium substrate by combining a sol-gel and a hydrothermal method. The bottom layer was flower-like and the upper layer was rod-shaped. The aluminium sheet coated with zinc oxide was infiltrated into a lubricating oil for 2 h to obtain an aluminium-based double-layer ZnO super-slippery surface. Testing showed that the surface demonstrated a good anti-fouling effect. The coating was hydrophobic and oleophobic, and even fruit juice and jam slipped down the surface at a small tilt angle (<5°). The corrosion resistance was also four orders of magnitude higher than that of the untreated aluminium sheet, and after three months, the anti-corrosion performance did not change significantly. Such good performance in the metal's corrosion resistance provides numerous potential application prospects.

Preparation and Light Trapping Properties of Double-Layered ZnO:Al Films with Textured Surface

A one-step wet-etching method was developed to prepare the transparent conducting double-layered ZnO:Al films with textured surface for improving the light trapping ability.In this work, we investigated the effects of different deposition and re-deposition conditions including Ar flow rate, working pressure and substrate temperature on the light trapping properties of double-layered ZnO:Al films. Obvious changes for surface morphology of double-layerd films were observed, which displayed the significant influence of the re-deposition process. The double-layered ZnO:Al films presented low resistivity, high optical transmittance and haze value in the visible region, which can meet the requirements of front electrodes.

Ultralong ZnO/Pt hierarchical structures for continuous-flow catalytic reactions

Grass-like double-layer ZnO micro-nanostructures in the confined microchannels is fabricated via fluid construction methods, with the vertical height as high as 50μm. Subsequently, surface modification of Pt solutions produced uniformly distributed catalytic Pt micro-nanostructures in a facile method. The efficiency of the grass-like catalysts was demonstrated for the continuous reduction reaction of o-nitrophenol and degradation methylene blue. Reaction rates and yields were significantly enhanced and the catalytic structures were recyclable. The results should be significant upon current microfluidic technologies, and exhibit great potentials in continuous flow reactions.

ZnO double layer film with a novel organic sensitizer as an efficient photoelectrode for dye–sensitized solar cells

Abstract A novel organic sensitizer, coded CR147, is applied to sensitize a ZnO–based dye–sensitized solar cell (DSSC). The common problem of ZnO dissolution and Zn 2+ /dye agglomeration, caused by the use of ruthenium–based dyes, is solved by the application of this CR147 dye. The highest power conversion efficiency ( η ) of 4.77% is achieved for the DSSC using a photoanode with a film of commercial ZnO nanoparticles (C ZnO) and the CR147 dye, while the η is only 3.41% for the DSSC with the commercial N719 dye. The cell performance with the CR147 dye is further improved by using a photoanode with the double layer ZnO film (D–ZnO), composed of an underlayer with coral–like ZnO nanocrystals and an overlayer with hexagonal club–like ZnO submicrocrystals. The DSSC with the D–ZnO film exhibits an η of 6.89%, which is ca. 45% higher than that of the DSSC with the C ZnO film (4.77%). This higher efficiency is attributed to the superior charge transfer and light–scattering abilities provided by coral–like ZnO nanocrystals and hexagonal clubs–like ZnO submicrocrystals, respectively, with reference to these parameters of C ZnO.

Excellent optical quality versus strong grain boundary effect in a double-layer ZnO structure

ZnO samples with a double-layer structure and top nanorod arrays on the bottom film layer were grown by metal-organic chemical vapor deposition at a temperature range from 340 to 400 °C. The ZnO nanorods show excellent optical quality and no obvious defect related emission can be detected below 40 K except for I6 line and the surface bound exciton emission. The free exciton emission and its phonon replicas dominate the near band edge emission between 40 and 295 K. For the film layer, the temperature-dependent Hall measurements showed that the conduction region is degenerate. In the conduction region, the carrier mobility is mainly limited by the grain boundary effect, which can be weakened by thermal annealing. The conduction mechanism in this region before and after annealing can be fitted by a uniform and a non-uniform conduction model, respectively. The results indicate that grain boundary effects strongly limit the mobility and consume large amounts of carriers by the trap states. Furthermore, we propose a qualitative model to explain the expansion of the conduction regions by annealing. It reveals a mechanism for the improvement of electrical properties of polycrystalline thin films by annealing treatments.

Synthesized of Double Layer Thin Film ZnO/ZnO:Ag by Sol-Gel Method for Direct Blue 71 Photodegradation

The objective of this paper is to synthesize and to characterize a single and a double layer ZnO and ZnO/ZnO:Ag thin films and their application for degradation of direct blue 71. Double layer (DL) thin films of zinc oxide and silver-doped zinc oxide (ZnO/ZnO:Ag) were deposited on the substrate glass by using sol-gel spray coating technique. Ag doping variations (2, 4, 6 and 8 %mol) into ZnO were studied. X-Ray Diffractometer (XRD) and UV-Vis spectrophotometer were used to analyze structure and optical properties of thin films. Direct Blue 71 (DB71) was used for photocatalytic evaluation under UV light irradiation. XRD result showed that all prepared thin films have wurtzite structure with better crytalinity compared to double layer preparation and increasing concentration of Ag doping. UV-Vis transmittance spectra showed that decreasing of transparency of films followed by DL preparation and Ag doping concentration. By using envelope method, energy gap of films can be determined. ZnO/ZnO:Ag 6% (DL 6%) indicated the smallest energy gap 3,038 eV. The highest DB71 degradation result under UV light irradiation was reached by DL 6% with 55.43% and 8.56 x 10 -3 min -1 for photocatalytic efficiency and photodegradation rate, respectively.

Dye-sensitized solar cells based on a 1D/3D double-layered ZnO photoanode with improved photovoltaic performance

The ZnO ellipsoids and spheres are fabricated via a facile sonochemical process. Dye-sensitized solar cells based on 1D/3D double layered ZnO photoanode are designed. The ZnO ellipsoids and spheres show superior light scattering ability in DSSCs.

Double-layered ZnO nanostructures for efficient perovskite solar cells.

To date, a single layer of TiO2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solution-processed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field.

Texture-etched broad surface features of double-layered ZnO:Al transparent conductive films for high haze values

A multi-step chemical wet-etching method, with a process of ZnO:Al (AZO) deposition, NH3⋅H2O etching, AZO re-deposition and HCl re-etching, is developed to obtain a wide range distribution of texture features for improving the light trapping. The first mild step with a NH3⋅H2O etching process (for 4min) results in tiny craters with a lateral feature size of 100–400nm and root mean square (RMS) roughness of 34.5nm, which provides an effective light trapping for the short wavelength. The second HCl etching (for 15s) aims at texturing strong pits with ∼1.5μm feature size and ∼75nm RMS, which leads to enhanced light trapping in the long wavelength. The diffuse transmittance increases from 9.0% to 51.6% due to the enhanced light scattering by the double-layered texture with the NH3⋅H2O and HCl etching processes. The corresponding highest haze value of 59.6% is obtained compared to that of 6.8% at 550nm due to the re-etching process for the NH3⋅H2O-etched sample. This multi-step method will lead to a broad surface feature distribution of 100–1500nm, where the electrical properties remain a slight change. Such good double texture surfaces prepared by the novel etching method promote the potential application of AZO films in thin film solar cells.

Influence of precursor solution's concentration on double-layer ZnO structure and solar cell's performance

In this letter, we discuss the influences of precursor solution's concentration on the double-layer structure of ZnO and the performance of CdS-sensitized solar cells. In the scanning electron microscopy (SEM) images, we found that the concentration of precursor solution only had influence on the growth of ZnO on the upper-layer. In the X-ray diffraction (XRD) patterns, we found that when the concentration was 0.05M, ZnO crystal growth along c-axis was very strong and ZnO had good crystallinity. We also measured the photocurrent–voltage (I–V) characteristics of CdS-sensitized solar cells. When the concentration is 0.05M, conversion efficiency reaches to 1.01%.

CdS and CdSe quantum dots subsectionally sensitized solar cells using a novel double-layer ZnO nanorod arrays

We report a novel approach for synthesizing CdS and CdSe quantum dots subsectionally sensitized double-layer ZnO nanorods for solar cells, which are comprised of CdS QDs-sensitized bottom-layer ZnO NRs and CdSe QDs-sensitized top-layer ZnO NRs. X-ray diffraction study and scanning electron microscopy analysis indicate that the solar cells of subsectionally sensitized double-layer ZnO NRs, which are the hexagonal wurtzite crystal structure, have been successfully achieved. The novel structure enlarged the range of absorbed light and enhanced the absorption intensity of light. The I–V characteristics show that the double-layer structure improved both the current density (Jsc) and fill factor (FF) by 50%, respectively, and power conversion efficiency (η) was increased to twice in comparison with the CdS QDs-sensitized structure.

Advanced light trapping materials: Double layer ZnO:B based transparent conductive oxide

We present double layer structures consisting of ZnO:B/ZnO:B (BZO) and In 2O 3:Mo (IMO)/BZO films. The structure offers the unique opportunity of separating the conductivity of transparent conductive oxides from their light scattering behavior and allows their optimization for use in thin film solar cells. The layers serve as carrier transport and light trapping layers, respectively. BZO films were prepared by mid-frequency magnetic sputtering from a ZnO:B 2O 3 ceramic target. In order to enhance the conductivity of the BZO films, hydrogen was introduced into the sputtering atmosphere. Introducing hydrogen increased the mobility of the BZO-based double layer films to near 30 cm 2/V•s. Efficient scattering was achieved by etching the film in dilute hydrochloric acid. IMO films were also tested as the transport layer. An unconventional surface morphology was obtained by etching the IMO/BZO double layer film. Using this cascading multilayer structure IMO/BZO film as the front contact in a-Si:H solar cell, 20.4% and 7.4% enhancements in short circuit current density were obtained compared to smooth IMO films and textured single layer BZO films.

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis**Project supported by Hi-Tech Research and Development Program of China (Grant Nos. 2007AA05Z436 and 2009AA050602),Science and Technology Support Project of Tianjin (Grant No. 08ZCKFGX03500), the National Basic Research Program of China (Grant Nos. 2011CB201605 and 2011CB201606), the National Natural Science Foundation of China (Grant No. 60976051),

Indium doped zinc oxide (ZnO:In) thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate. 1 and 2 at.% indium doped single-layer ZnO:In thin films with different amounts of acetic acid added in the initial solution were fabricated. The 1 at.% indium doped single-layers have triangle grains. The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82×10−3 Ω·cm and particle grains. The double-layers structure is designed to fabricate the ZnO:In thin film with low resistivity (2.58×10−3 Ω·cm) and good surface morphology. It is found that the surface morphology of the double-layer ZnO:In film strongly depends on the substrate-layer, and the second-layer plays a large part in the resistivity of the double-layer ZnO:In thin film. Both total and direct transmittances of the double-layer ZnO:In film are above 80% in the visible light region. Single junction a-Si:H solar cell based on the double-layer ZnO:In as front electrode is also investigated.