Showing papers on "Chemical bath deposition published in 2014"

Nanocrystalline Rutile Electron Extraction Layer Enables Low-Temperature Solution Processed Perovskite Photovoltaics with 13.7% Efficiency

Abstract: We demonstrate low-temperature (70 °C) solution processing of TiO2/CH3NH3PbI3 based solar cells, resulting in impressive power conversion efficiency (PCE) of 13.7%. Along with the high efficiency, a strikingly high open circuit potential (VOC) of 1110 mV was realized using this low-temperature chemical bath deposition approach. To the best of our knowledge, this is so far the highest VOC value for solution-processed TiO2/CH3NH3PbI3 solar cells. We deposited a nanocrystalline TiO2 (rutile) hole-blocking layer on a fluorine-doped tin oxide (FTO) conducting glass substrate via hydrolysis of TiCl4 at 70 °C, forming the electron selective contact with the photoactive CH3NH3PbI3 film. We find that the nanocrystalline rutile TiO2 achieves a much better performance than a planar TiO2 (anatase) film prepared by high-temperature spin coating of TiCl4, which produces a much lower PCE of 3.7%. We attribute this to the formation of an intimate junction of large interfacial area between the nanocrystalline rutile TiO2 ...

Highly reproducible planar Sb2S3-sensitized solar cells based on atomic layer deposition

Abstract: A high-quality Sb2S3 thin-absorber with controllable thickness was reproducibly formed by atomic layer deposition (ALD) technique. Compared with conventional chemical bath deposition (CBD), the Sb2S3 absorber deposited by ALD did not contain oxide or oxygen impurities and showed a very uniform thickness of Sb2S3 absorbers formed on a rough surface of dense blocking TiO2/F-doped SnO2 (bl-TiO2/FTO) substrate. The planar ALD-Sb2S3 solar cells comprised of Au/Poly-3-hexylthiophene/ALD-Sb2S3/bl-TiO2/FTO showed significantly improved power conversion efficiency of 5.77% at 1 sun condition and narrow efficiency deviation, whereas the planar CBD-Sb2S3 solar cells exhibited 2.17% power conversion efficiency. The high efficiency and good reproducibility of ALD-Sb2S3 solar cell devices is attributed to reduced backward recombination because of the inhibition of oxide defects within ALD-Sb2S3 absorber and the conformal deposition of very uniform Sb2S3 absorbers on the blocking TiO2 surface by ALD process.

Enhanced supercapacitive performance of chemically grown cobalt-nickel hydroxides on three-dimensional graphene foam electrodes.

Abstract: Chemical growth of mixed cobalt–nickel hydroxides (CoxNi1–x(OH)2), decorated on graphene foam (GF) with desirable three-dimensional (3D) interconnected porous structure as electrode and its potential energy storage application is discussed. The nanostructured CoxNi1–x(OH)2 films with different Ni:Co (x) compositions on GF are prepared by using the chemical bath deposition (CBD) method. The structural studies (X-ray diffraction and X-ray photoelectron spectroscopy) of electrodes confirm crystalline nature of CoxNi1–x(OH)2/GF and crystal structure consists of Ni(OH)2 and Co(OH)2. The morphological properties reveal that nanorods of Co(OH)2 reduce in size with increases in nickel content and are converted into Ni(OH)2 nanoparticles. The electrochemical performance reveals that the Co0.66Ni0.33(OH)2/GF electrode has maximum specific capacitance of ∼1847 F g–1 in 1 M KOH within a potential window 0 to 0.5 V vs Ag/AgCl at a discharge current density of 5 A g–1. The superior pseudoelectrochemical properties of c...

Double Role of HMTA in ZnO Nanorods Grown by Chemical Bath Deposition

Abstract: ZnO nanorods (NRs) grown by chemical bath deposition (CBD) are among the most promising semiconducting nanostructures currently investigated for a variety of applications. Still, contrasting experimental results appear in the literature on the microscopic mechanisms leading to high aspect ratio and vertically aligned ZnO NRs. Here, we report on CBD of ZnO NRs using Zn nitrate salt and hexamethylenetetramine (HMTA), evidencing a double role of HMTA in the NRs growth mechanism. Beyond the well-established pH buffering activity, HMTA is shown to introduce a strong steric hindrance effect, biasing growth along the c-axis and ensuring the vertical arrangement. This twofold function of HMTA should be taken into account for avoiding detrimental phenomena such as merging or suppression of NRs, which occur at low HMTA concentration.

Co-doped NiO nanoflake array films with enhanced electrochromic properties

Abstract: Co-doped NiO electrochromic nanoflake array films grown on FTO with antireflection ability have been synthesized by low temperature chemical bath deposition. Co doping has an influence on the growth and electrochromic properties of NiO nanoflake arrays. Noticeably, all the films show a very high transmittance at the bleached state in the region of visible light. Compared to the undoped NiO, the 1% Co-doped NiO nanoflake array film exhibits outstanding electrochromism, including large transmittance modulation (88.3%), high coloration efficiency (47.7 cm2 C−1), fast switching speed (3.4 s and 5.4 s), excellent reversibility and cycling durability at a wavelength of 550 nm. The enhanced electrochromic performances can be attributed to the synergetic effect contribution from low crystallization, oblique nanoflake array configuration and improved p-type conductivity by appropriate Co doping.

New Insight into Copper Sulfide Electrocatalysts for Quantum Dot-Sensitized Solar Cells: Composition-Dependent Electrocatalytic Activity and Stability

Abstract: Despite recent significant strides in understanding various processes in quantum dot-sensitized solar cells (QDSSCs), little is known about the intrinsic electrocatalytic properties of copper sulfides that are the most commonly employed electrocatalysts for the counter electrode of QDSSCs. Given that the physical properties of copper sulfides are governed by their stoichiometry, the electrocatalytic activity of copper sulfides toward polysulfide reduction may also be dictated by their compositions. Using a new, simple approach to prepare robust copper sulfide films based on chemical bath deposition (CBD), we were able to delicately control the compositions of copper sulfides, which allowed us to perform a systematic investigation to gain new insight into copper sulfide-based electrocatalysts. The electrocatalytic activity is indeed dependent on the compositions of copper sulfides: Cu-deficient films (CuS and Cu1.12S) are superior to Cu-rich films (Cu1.75S and Cu1.8S) in their electrocatalytic activity. In...

Highly selective and sensitive CdS thin film sensors for detection of NO2 gas

Abstract: We demonstrate the preparation of cadmium sulfide (CdS) thin films via a facile chemical bath deposition method. The CdS films have been characterized by various techniques, such as, X-ray diffraction (XRD), energy dispersive X-ray (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Gas sensing performance of CdS thin films was tested at room temperature (38 °C) for oxidizing (NO2, Cl2) and reducing gases (H2S, NH3, C2H5OH, CH3OH). CdS films were found to be highly selective and sensitive to NO2 with a maximum response of 61% at 200 ppm with a fast response time of 50 s and 81% stability. Furthermore, the sensor is able to detect up to low (5 ppm) concentration of NO2 gas with a reasonable response (5%). The plausible mechanism(s) of NO2 sensing has been discussed.

Chemical Bath Deposition of Stoichiometric CdSe Quantum Dots for Efficient Quantum-Dot-Sensitized Solar Cell Application

Abstract: Cadmium selenide (CdSe) quantum dots (QDs) have been prepared by suppressing the formation of an amorphous selenium oxide (SeO2) layer on the surface of CdSe QDs. The precursor ratio for the chemical bath deposition was optimized to minimize the SeO2 layer growth and develop high-efficiency CdSe QDs for quantum-dot-sensitized solar cell (QDSSC) applications. The morphologies and optical and electrical properties of the CdSe QDs were investigated, and the growth mechanism was also proposed for the CdSe and SeO2 layer formation. Furthermore, electrochemical impedance spectroscopy results indicated that the SeO2 layer reduced the recombination resistance of photogenerated electron–hole pairs, thus degrading the cell efficiency. Therefore, a QDSSC based on an optimized CdSe/CdS/ZnO nanowire photoanode, polysulfide electrolyte, and Au counter electrode can enhance the power conversion efficiency to 4.8% under AM 1.5 G one-sun illumination.

ZnO Micro/Nanocrystals with Tunable Exposed (0001) Facets for Enhanced Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate

Abstract: ZnO micro/nanocrystals with different percentages of the exposed (0001) facets were synthesized by a facile chemical bath deposition method. Various characterizations were carried out to understand...

Selective area growth of well-ordered ZnO nanowire arrays with controllable polarity.

Abstract: Controlling the polarity of ZnO nanowires in addition to the uniformity of their structural morphology in terms of position, vertical alignment, length, diameter, and period is still a technological and fundamental challenge for real-world device integration. In order to tackle this issue, we specifically combine the selective area growth on prepatterned polar c-plane ZnO single crystals using electron-beam lithography, with the chemical bath deposition. The formation of ZnO nanowires with a highly controlled structural morphology and a high optical quality is demonstrated over large surface areas on both polar c-plane ZnO single crystals. Importantly, the polarity of ZnO nanowires can be switched from O- to Zn-polar, depending on the polarity of prepatterned ZnO single crystals. This indicates that no fundamental limitations prevent ZnO nanowires from being O- or Zn-polar. In contrast to their catalyst-free growth by vapor-phase deposition techniques, the possibility to control the polarity of ZnO nanowi...

High performance PbS quantum dot sensitized solar cells via electric field assisted in situ chemical deposition on modulated TiO2 nanotube arrays

Abstract: Quantum dot sensitized solar cells (QDSSCs) are attractive photovoltaic devices due to their simplicity and low material requirements. However, efforts to realize high efficiencies in QDSSCs have often been offset by complicated processes and expensive or toxic materials, significantly limiting their useful application. In this work, we have realized for the first time, high performance PbS QDSSCs based on TiO2 nanotube arrays (NTAs) via an in situ chemical deposition method controlled by a low electric field. An efficiency, η, of ~3.41% under full sun illumination has been achieved, which is 133.6% higher than the best result previously reported for a simple system without doping or co-sensitizing, and comparable to systems with additional chemicals. Furthermore, a high open-circuit voltage (0.64 V), short-circuit current (8.48 mA cm(-2)) and fill factor (0.63) have been achieved. A great increase in the quantity of the loaded quantum dots (QDs) in the NTAs was obtained from the in situ electric field assisted chemical bath deposition (EACBD) process, which was the most significant contributing factor with respect to the high JSC. The high VOC and FF have been attributed to a much shorter electron path, less structural and electronic defects, and lower recombination in the ordered TiO2 NTAs produced by oscillating anodic voltage. Besides, the optimal film thickness (~4 μm) based on the NTAs was much thinner than that of the control cell based on nanoporous film (~30.0 μm). This investigation can hopefully offer an effective way of realizing high performance QDSSCs and QD growth/installation in other nanostructures as well.

Controlled Growth of CoSx Nanostrip Arrays (CoSx‐NSA) on Nickel Foam for Asymmetric Supercapacitors

Abstract: This article is free to read on the publishers website A high‐energy‐density asymmetric supercapacitor based on cobalt sulfide nanostrip arrays (CoSx‐NSA) as the cathode and reduced graphene oxide as the anode has been prepared; the CoSx‐NSA was synthesized on three‐dimensional (3D) nickel (Ni) foam by using a simple and scalable chemical bath deposition (CBD) method. The reduced graphene oxide sheets were deposited on the Ni foam by hydrothermal treatment of the foam in a graphene oxide solution. Novel and unique nanostructured architectures of the CoSx electrode provide a large effective surface area. In addition, both of the electrode materials are directly grown on the substrate without any conductive additives or binders, avoiding unnecessary materials. The asymmetric supercapacitor device operates in a wider potential window, achieving a remarkably high energy density, excellent rate capability, and long‐term cycling stability. These attractive results make CoSx‐NSA a promising material for asymmetric supercapacitors of high energy and power density, utilizing an aqueous electrolyte solution.

N-doped amorphous carbon coated Fe3O4/SnO2 coaxial nanofibers as a binder-free self-supported electrode for lithium ion batteries.

Abstract: N-doped amorphous carbon coated Fe3O4/SnO2 coaxial nanofibers were prepared via a facile approach. The core composite nanofibers were first made by electrospinning technology, then the shells were conformally coated using the chemical bath deposition and subsequent carbonization with polydopamine as a carbon source. When applied as a binder-free self-supported anode for lithium ion batteries, the coaxial nanofibers displayed an enhanced electrochemical storage capacity and excellent rate performance. The morphology of the interwoven nanofibers was maintained even after the rate cycle test. The superior electrochemical performance originates in the structural stability of the N-doped amorphous carbon shells formed by carbonizing polydopamine.

Influence of Cu vacancy on knit coir mat structured CuS as counter electrode for quantum dot sensitized solar cells.

Abstract: Knit-coir-mat-like structured CuS thin films prepared by chemical bath deposition with different time duration were used as counter electrode in qunatum dot sensitized solar cells. The film deposited at 4 h exhibited better electrochemical and photovoltaic performance with JSC, VOC, and FF values of 14.584 mA cm–2, 0.566 V, and 54.57% and efficiency of 4.53%. From the UV–vis absorption spectra, it is observed that CuS thin film exhibits free carrier intraband absorption in the longer wavelengh region. The enhanced performance of CuS counter electrodes is due to Cu vacancies with increased S composition, and the quasi-Fermi energy level in semiconductors with respect to electrolyte redox potential is one of the causes that affects the electrocatalytic activity of counter electrodes.

Chemically deposited cubic structured CdO thin films: Use in liquefied petroleum gas sensor

Abstract: Cadmium oxide (CdO) thin films have been synthesized by chemical bath deposition (CBD) method. The deposition is carried out at room temperature (300 K). The surface morphology of the CdO thin films showed interconnected prism-like structure. The CdO thin films are oriented along (1 1 1) plane with the cubic crystal structure. The sensing properties of nanostructured CdO thin films have been studied for liquefied petroleum gas (LPG) at operating temperature of 573 K. The CdO thin films exhibited maximum gas response of 44% upon the LPG exposure of 1040 ppm.

Core-shell NiFe2O4@TiO2 nanorods: an anode material with enhanced electrochemical performance for lithium-ion batteries.

Abstract: hierarchical porous core-shell nife2o4@tio2 nanorods have been fabricated with the help of hydrothermal synthesis, chemical bath deposition, and a subsequent calcinating process. the nanorods with an average diameter of 48 nm and length of about 300-600 nm turn out have a highly uniform morphology and are composed of nanosized primary particles. owing to the synergistic effect of individual constituents as well as the hierarchical porous structure, the novel core-shell nife2o4@tio2 nanorods exhibit superior electrochemical performance when evaluated as anode materials for lithium-ion batteries. at the current density of 100 ma g(-1), the composite exhibits a reversible specific capacity of 1034 mah g(-1) up to 100 charge-discharge cycles, which is much higher than the uncoated nife2o4 nanorods. even when cycled at 2000 ma g(-1), the discharge capacity could still be maintained at 358 mah g(-1).

Substitution of the CdS buffer layer in CIGS thin-film solar cells

Abstract: This contribution provides an overview of current activities in the area of alternative buffer layers for Cu(In,Ga)(S,Se)2 (CIGS) thin-film solar cells. Good cell and module results were achieved by replacing the standard Cds buffer with Zn(O,S), In2S3, (Zn,Sn)Oy or (Zn,Mg)O grown by various methods like chemical bath deposition (CBD), thermal evaporation, sputtering, atomic layer deposition, and spray ion layer gas reaction. The “dry” deposition methods like sputtering and thermal evaporation could be favorable in an industrial environment on glass substrates or application in a roll-to-roll coater. Significant progress was made within the last two years for various Cd-free CIGS devices. We list current records for cells with alternative buffers, e. g. Zn(O,S)-buffered champion cells with efficiencies between 18—20 % and In2S3-buffered cells with 16—17 %. Both materials have the potential to substitute CdS with efficiencies approaching the 20 % mark already surpassed by CIGS cells with CBD CdS buffers.

Electrochemical performance of a portable asymmetric supercapacitor device based on cinnamon-like La2Te3prepared by a chemical synthesis route

Abstract: A cinnamon-like La2Te3 nanostructure has been prepared by a simple chemical bath deposition (CBD) route. Field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy techniques have been used to characterize the morphological and structural properties of the La2Te3 thin films. The prepared La2Te3 thin film electrodes are applied in a supercapacitor, in which they exhibited a high specific capacitance value of 469 F g−1 at a scan rate of 2 mV s−1 with an excellent cycling performance up to 1000 cycles. Even at a specific power of 2.5 kW kg−1, the La2Te3 electrode possessed a specific energy of ∼126 Wh kg−1. At a relatively high discharge current density of 4 mA cm−2, the specific capacitance was still maintained at 220 F g−1. Furthermore, portable La2Te3 asymmetric supercapacitor devices have been fabricated using an aqueous 1 M KOH electrolyte with good specific energy and specific power. Such an impressive portable asymmetric supercapacitor is a promising candidate for applications in high-performance energy storage systems.