Two-step Chemical Bath Deposition Research Articles

Heterostructured In2O3/In2S3 hollow fibers enable efficient visible-light driven photocatalytic hydrogen production and 5-hydroxymethylfurfural oxidation

Solar light driven hydrogen production from water splitting and oxidation of biomass-derivatives is attractive for the conversion of solar energy to high value-added chemicals. The fabrication of heterostructure photocatalysts with matched band structure between two semiconductors is a promising approach for efficient photocatalysis. In this work, a novel In2O3/In2S3 heterostructured hollow fiber photocatalyst was successfully fabricated through two-step ion exchange and chemical bath deposition methods, where the In2S3 nanoparticles (NPs) anchored on the surface of In2O3 hollow fibers via strong interfacial interaction between the In2O3 (222) and In2S3 (220) facets. The photocatalyst was used for efficient visible-light-driven photocatalytic hydrogen production integrated with selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). Compared with pristine In2O3 and In2S3, the optimal In2O3/In2S3 heterostructure exhibits an enhanced photocatalytic hydrogen production rate (111.2 μmol h−1 g−1), HMF conversion efficiency (56%) and DFF selectivity (68%) under visible light irradiation. The experimental and theoretical investigations illustrate the phase interface between well matched In2O3 (222) and In2S3 (220) facets gives rise to facilitated photogenerated charge separation and transfer. This study presents the development of high-performance heterostructured photocatalysts for high efficient hydrogen production coupled with biomass oxidation.

Interfacial competing interaction eliminates voids in the buried interface for efficient and stable perovskite solar modules on bare NiOX

Perovskite solar cells (PSCs) with impressive efficiency is promising for commercialization. However, when scaling up PSCs to large-area perovskite solar modules (PSMs), the rapid degradation of performance and stability still remains a grand challenge. One of the main causes of the degradation is the presence of local voids in the buried interface for large-area films, which we find could be attributed to the unbalanced interfacial interaction between precursor solvent and substrate. Here we improve a scalable and low-temperature sequential two-step chemical bath deposition process aiming for high quality NiOX. Further with the modulation of A-site cations to enhance the interaction between DMSO and perovskite precursor, the potential for DMSO absorbing on the NiOX could be eliminated. This strategy can inhibit the delay movement of DMSO on NiOX and improve the buried interfacial quality, with compact morphology and absent of voids. The inverted structured PSCs and PSMs based on the bare NiOX and modified perovskite precursor reach a champion efficiency of 22.40% and 19.09%, respectively, which are both among the highest reported values. The highly efficient PSMs also exhibit a long-term operational stability, which retain 84% of the initial performance after 1056 h operating under one-sun illumination.

Rational design of binder free NiFe2O4@CoFe2O4 core–shell nanoflake arrays synthesized by chemical bath deposition for supercapacitor application

In recent years, exploiting stable and high-performance electrode materials has attracted researchers interest as the demand for clean, efficient, and sustainable energy storage devices grows. In this study, facile NiFe2O4@CoFe2O4 core-shell nanoflake arrays grown on flexible stainless steel mesh (FSSM) were synthesized by a simple, low-cost two-step chemical bath deposition (CBD) method. The synergistic influence between NiFe2O4 nanoflake arrays and CoFe2O4 nanoflakes in the mesh form electrode that show a quick electron/ion transfer and a higher electrical conductivity. The NiFe2O4@CoFe2O4 core-shell nanoflake array electrode has shown a capacitance of 1459.4 F g−1 at a current density of 4 mA cm−2, which is significantly higher than the capacitances of the pristine NiFe2O4 and CoFe2O4 electrode. The NiFe2O4@CoFe2O4 core-shell nanoflake array electrode shows superb cycling stability with 85 % retention over 5000 cycles at a high current density of 20 mA cm−2. Furthermore, the NiFe2O4@CoFe2O4 core-shell nanoflake array symmetric device demonstrated a high energy density of 21.15 W h kg−1 at a power density of 0.466 k W kg−1. The improved electrochemical performance is attributed to its unique hierarchical structure, which allows for efficient ion and electron transport, a high number of active sites, and a synergistic impact. This novel integrated nanoarchitecture could hold significant promise as improved electrodes for high-performance supercapacitors due to its remarkable electrochemical performance and cost-effective production procedure.

Yttrium (Y) doped ZnO nanowire/p-Si heterojunction devices for efficient self-powered UV-sensing applications

In the current work, n-type Y-doped ZnO nanowires (n-Y:ZnO) and p-type Si heterojunctions are fabricated by employing two-step chemical bath deposition (CBD) process. The work demonstrates the systematic incorporation of Y in ZnO nanowires for achieving the low power UV response. The crystalline nature, morphology, chemical compositions of doped nanowires are studied extensively by employing XRD, FESEM, HRTEM, elemental mapping, EDS and XPS. The change in defect states due to Y incorporation has been studied in detail by using deconvoluated PL spectra. The results indicate that ZnO nanowires exhibit Zn interstitials dependent huge UV/blue luminescence and oxygen vacancy related lowest green luminescence simultaneously for selective 1% Y-doping. The best self-powered photoresponse has been achieved for 1% Y-doped ZnO nanowires/p-Si heterojunction under relatively low power UV illumination (374 nm @5 mW/cm2). More significantly, at self-powered mode, such heterojunction has been delivered a stable and fast (<1 s) photoresponse with a maximum responsivity of 225 mA/W and high On/Off ratio of ∼104. The work provides an insight into the fabrication of heterojunction UV detectors for next-generation self-powered, large area optoelectronic devices.

Antireflective and nanocolumnar-shaped Mn:ZnO films grown by chemical bath deposition

In the present study, intriguing nanocolumnar-shaped Mn-doped ZnO (Mn:ZnO) films have been prepared by a simple and scalable two-step chemical bath deposition technique. Firstly, the ZnO nano-seeds were deposited on a glass substrate, and in the second step, the hexagonal pyramidal-shaped Mn:ZnO arrays were grown regularly as well as vertically based on the ZnO seeds. The optical properties of the nanocolumnar-shaped Mn:ZnO films have been investigated in detail. Interestingly, the reflectance measurements demonstrate that the nanocolumnar-shaped Mn:ZnO films are an excellent candidate for antireflection coatings, showing a significantly low reflectance over the entire visible spectrum. The inverse hexagonal pyramidal-shaped Mn:ZnO films with antireflection and photon-trapping properties have great potential for their integration into nanoscale devices, especially thin-film solar cells.

Self-rectifying threshold resistive switching based non-volatile memory of CBD/CBD grown vertical n-ZnO nanowire/p-Si heterojunction diodes

Vertically oriented ZnO nanowires are grown on p-Si substrate by employing two-step sequential chemical bath deposition technique. The ZnO nanowire exhibits n-type doping due to the presence of oxygen vacancies. The electrical characterizations of n-ZnO NWs/p-Si heterojunction diodes exhibit a self-rectifying, threshold resistive switching behavior. Such switching behavior is explained by oxygen vacancy assisted conducting filament formation mechanism. The relevant charge transport is governed by TC-SCLC and multistep recombination-tunneling processes through the interface traps. Threshold-voltage for resistive switching is observed to be increasing with increasing bias sweep rate. The device shows superior memory endurance for forward and reverse voltage sweep of 50 cycles in fast sweep mode. The ratio of HRS to LRS resistances shows one order of difference. The retention time of such resistive switching memory is recorded to be 4000 seconds, suggesting its non-volatile functionality. Thus, the n-ZnO NWs/p-Si heterojunction can be employed for fabricating promising non-volatile memory devices with excellent endurance and retentions. Copyright © 2018 VBRI Press.

Enhancement of performance of Ga incorporated ZnO UV photodetectors prepared by simplified two step chemical solution process

The present study establishes the UV photodetector capability of Zinc Oxide (ZnO) and Gallium incorporated ZnO (GZO) thin films prepared by a simplified two-step chemical bath deposition technique. The prepared UV detectors were characterized by tools such as XRD, SEM, UV, PL and Photoresponse to investigate their properties. The structural study revealed the enhancement of film crystallinity with respect to Ga doping level. The optical studies confirm the higher absorption at UV range for 3% Ga doped ZnO film. From PL study, the green emission observed at 522 nm is associated with the defects from oxygen vacancies (Vo+). Once the UV light is irradiated on the GZO film surface, electrons and holes are generated as the illumination energy is larger than the ZnO bandgap energy, known as above-band energy illumination. The photo-generated holes then neutralize the chemisorbed ions causing the release of electrons in the conduction band of ZnO, this could increase the photocurrent. In this study, the calculated photo-detectivity (D*), responsivity (R) and external quantum efficiency (EQE) of the prepared UV detectors are 1.24 ×1010 jones, 0.38 AW-1, and 125.10% respectively for 3% Ga doped ZnO film. These parameters are noticeable and this study proves that GZO films in fact work as good sensitive UV detectors.

Influence of Temperature on ZnO/Co3O4 Nanocomposites for High Energy Storage Supercapacitors.

We developed a two-step chemical bath deposition method followed by calcination for the production of ZnO/Co3O4 nanocomposites. In aqueous reactions, ZnO nanotubes were first densely grown on Ni foam, and then flat nanosheets of Co3O4 developed and formed a porous film. The aspect ratio and conductivity of the Co3O4 nanosheets were improved by the existence of the ZnO nanotubes, while the bath deposition from a mixture of Zn/Co precursors (one-step method) resulted in a wrinkled plate of Zn/Co oxides. As a supercapacitor electrode, the ZnO/Co3O4 nanosheets formed by the two-step method exhibited a high capacitance, and after being calcined at 450 °C, these nanosheets attained the highest specific capacitance (940 F g–1) at a scan rate of 5 mV s–1 in the cyclic voltammetry analysis. This value was significantly higher than those of single-component electrodes, Co3O4 (785 F g–1) and ZnO (200 F g–1); therefore, the presence of a synergistic effect was suggested. From the charge/discharge curves, the specific capacitance of ZnO/Co3O4 calcined at 450 °C was calculated to be 740 F g–1 at a current density of 0.75 A g–1, and 85.7% of the initial capacitance was retained after 1000 cycles. A symmetrical configuration exhibited a good cycling stability (Coulombic efficiency of 99.6% over 1000 cycles) and satisfied both the energy density (36.6 Wh kg–1) and the power density (356 W kg–1). Thus, the ZnO/Co3O4 nanocomposite prepared by this simple two-step chemical bath deposition and subsequent calcination at 450 °C is a promising material for pseudocapacitors. Furthermore, this approach can be applied to other metal oxide nanocomposites with intricate structures to extend the design possibility of active materials for electrochemical devices.

Two-step chemical bath deposition enhanced mobility of PbS thin films

A two-step chemical bath deposition (CBD) method that involves the deposition of films at two different bath temperatures is developed to enhance the grain growth and hole mobility of lead sulfide (PbS) thin films. The films deposited at three different conditions; first at 60 °C for 2 h, second at 30 °C for 1 h and at 60 °C for the subsequent 1 h, and finally at 60 °C for 1 h and at 30 °C for the subsequent hour. The deposition of PbS at only 60 °C for 2 h leads to the formation of cubic crystals with different sizes and hole mobility of 43.8 cm2V−1s−1. The deposition at a low temperature of 30 °C for the initial 1 h followed by the deposition at a high temperature of 60 °C for the subsequent hour increases the grain size and hole mobility to 62.2 cm2V−1s−1. However, the deposition of PbS at a high temperature of 60 °C for 1 h followed by the deposition at a low temperature of 30 °C for the subsequent hour decreases the grain size and hole mobility to 32.1 cm2V−1s−1. The PbS film deposited at low temperature in the first step acts as a seed layer for the growth of large-grained PbS in the second step. Thus, the two-step CBD method enhances the grain growth and hole mobility of PbS films. Hence, the two-step CBD method is very much useful for the growth of PbS for its applications in optoelectronic devices.

STUDY THE OPTICAL PROPERTIES OF THE VARIOUS DEPOSITION SOLUTIONS OF ZnO NANORODS GROWN ON GLASS SUBSTRATE USING CHEMICAL BATH DEPOSITION TECHNIQUE

In this study, two-step chemical bath deposition (CBD) technique has been employed for the fabrication of Zinc Oxide (ZnO) nanorods at low temperature. The ZnO nano-seed layer was deposited on the glass substrate using a radio frequency sputtering discharge technique. The impact of three zinc salts with Hexamethylenetetramine (HMTA) on the properties of ZnO nanorods have been investigated. The double beam UV visible (UV4100) spectrometer, micro-Raman scattering, and Field emission scanning electron microscopy (FESEM) were used to characterize and study the optical properties, energy band gap, defects, Raman spectra, phase orientation, quality of material, the interaction of phonons, transport properties, and the morphology of synthesized ZnO nanorods (NRs), respectively. The three zinc salts are Zinc Nitrate Hexahydrate, Zinc Acetate, and Zinc Chloride. The results found that the variation in zinc salts types with Hexamethylenetetramine as deposition solution is play a very important impact on the structures of fabricated ZnO nanorods that effected directly on the optical properties, energy band, material quality, and phase orientation of ZnO NRs. Also, from UV measurement the optical properties and energy band gap of produced ZnO nanorods are changed with changing the zinc salt as a precursor of deposition solution.

Construction of 1D/2D α-Fe2O3/SnO2 Hybrid Nanoarrays for Sub-ppm Acetone Detection.

Exhaled acetone is one of the representative biomarkers for the noninvasive diagnosis of type-1 diabetes. In this work, we have applied a facile two-step chemical bath deposition method for acetone sensors based on α-Fe2O3/SnO2 hybrid nanoarrays (HNAs), where one-dimensional (1D) FeOOH nanorods are in situ grown on the prefabricated 2D SnO2 nanosheets for on-chip construction of 1D/2D HNAs. After annealing in air, ultrafine α-Fe2O3 nanorods are homogenously distributed on the surface of SnO2 nanosheet arrays (NSAs). Gas sensing results show that the α-Fe2O3/SnO2 HNAs exhibit a greatly enhanced response to acetone (3.25 at 0.4 ppm) at a sub-ppm level compared with those based on pure SnO2 NSAs (1.16 at 0.4 ppm) and pure α-Fe2O3 nanorods (1.03 at 0.4 ppm), at an operating temperature of 340°C. The enhanced acetone sensing performance may be attributed to the formation of α-Fe2O3–SnO2 n-n heterostructure with 1D/2D hybrid architectures. Moreover, the α-Fe2O3/SnO2 HNAs also possess good reproducibility and selectivity toward acetone vapor, suggesting its potential application in breath acetone analysis.

Photoelectrochemical Determination of Cu2+ Using a WO3/CdS Heterojunction Photoanode.

Copper ions are not only physiologically essential for life but also hazardous materials causing a series of neurodegenerative diseases. Photoelectrochemical (PEC) detection has attracted a large amount of focus as a potential strategy to develop Cu2+ ion sensors. However, relatively low photocurrent signals with poor antidisturbance ability and the limited concentration range have prevented its practical applications. Here, we designed a WO3/CdS heterojunction photoanode for the PEC determination of Cu2+ in aqueous solution through a simple two-step chemical bath deposition method. The obtained WO3/CdS photoanode had a nanoplate morphology and showed an enhanced photoresponsivity with a photocurrent density of 1.5 mA/cm2 at 1.23 V versus RHE under illumination. Naturally, it exhibited a low detection limit (0.06 μM) and wider range (0.5 μM to 1 mM) for Cu2+ PEC detection first, suggesting that the WO3/CdS heterojunction photoanode is a promising tool to monitor copper pollution in natural environments.

Structural, morphological and optical properties of ZnO nanorods grown on a ZnO:Ga seeded thin film: The role of chemical bath deposition precursor concentration at constant and varying II/VI molar ratios

ZnO nanorods (ZNRs) were synthesized on glass substrates coated with an optimized Ga-doped ZnO seed layer by a two-step chemical bath deposition technique at constant and varying Zn(NO3)2/C6H12N4 (II/VI) molar ratios of the precursor solutions for growth time of 90 and 180 min and growth temperature of 90° C. The effects of different equimolar precursor solution concentrations (Cs) ranging from 0.01–0.2 M, as well as the varying II/VI molar ratios (ranging from 1:0.1–1:2) of the growth solutions were investigated on the morphology, luminescence and optical properties of the ZNRs. The X-ray diffraction analysis revealed that the as-grown ZNRs have a crystalline hexagonal wurtzite structure and they were preferentially oriented along the c-axis in all cases. The crystallite size of the ZNRs and the relative intensity of the (002) peak were observed to increase with the increase in Cs and II/VI molar ratios of the precursor solution. An appreciable peak shift of the (002) plane of the ZNRs, to lower 2θ angle with increasing molar ratios of the Cs was observed. The scanning electron microscope images illustrated that the ZNRs morphologies improved, their lengths and diameters increased as the growth Cs and II/VI molar ratios were raised. The root means square surface roughnesses of the ZNRs were found to reduce from 70 to 22 as the II/VI molar ratios increased from 1:0.1 to 1:2. The photoluminescence (PL) spectra displayed the prominent Ultra violet (UV) and deep level emissions (DLE) in both instances. The exciton peak intensity increased to a maximum value up to 0.05 M Cs and the II/VI precursor ratio of unity and decreased when the Cs levels and molar ratios were increased further. The calculated PL emission intensity ratio (IUV/IDLE) was found to be 12.5, 1.9 and 0.8 for 0.01, 0.05 and 0.1 M, respectively, which suggests that the ZNRs grown with the higher equimolar Cs possessed a high optical quality. The UV–Vis analysis also showed greatly enhanced optical absorbance in the visible region at higher Cs and II/VI molar ratios. Similarly, the band gap energy decreased from 3.28–3.25 eV and from 3.30–3.24 eV with the increase in the Cs and II/VI molar ratios, respectively.

Controlling the morphology of ZnO NRs grown on GZO seed layer, by use of ethylenediamine and L-cysteine as crystal growth modifiers and complexing agents

Un-capped, ethylenediamine-capped (EDA-capped) and L-cysteine-capped (L-cyst.-capped) ZnO nanorods (ZNRs) were synthesized from an aqueous solutions of Zn(NO3)2 and (CH2)6N4 via a two-step chemical bath deposition method at a bath temperature of 90 °C for 3 h. The ZNRs were grown on a Ga-doped ZnO (GZO) seeded glass substrate. The effects of the EDA and the L-cysteine complexing agents and their concentrations (ranging from 0 to 2 mM) on the structural and optical properties of the ZNRs were studied using various techniques. The X-ray diffraction study showed that all the ZNRs that were grown had a strong c-axis preferred orientation irrespective of the capping agents used. The average crystallite sizes were approximated as 84, 77, 75, 106 and 107 nm for un-capped (0 mM), 0.5 EDA-capped, 2 mM EDA-capped, 0.5 L-cyst.-capped and 2 mM L-cyst.-capped ZNRs, respectively. Scanning electron microscope investigation of the samples showed successive decrease in the diameters and lengths of the particles with the increase in EDA-capping concentrations but an increase in particle sizes as the L-cyst.-capping levels increased. Novel changes in crystal shapes were realized at higher capping concentrations. Well-aligned, uniform and compactly packed arrays of hexagonal ZNRs were formed in the presence of the 0.5 mM L-cyst.-capping. The energy-dispersive X-ray spectroscopy analyses showed that the 0.5 mM L-cyst.-capped sample presents the Zn/O ratio to the proximity of 1. The photoluminescence (PL) and cathodoluminescence emissions spectra showed the main peaks of ZnO, which varied in similar trends with changes in the type and concentrations of the capping agents. The highest PL emission peak intensity was obtained at a capping ratio of 0 mM, and 0.5 mM L-cysteine. The values of the absorption edges observed were in the range of 384–397 nm, while the absorption peaks ranged between 361 and 372 nm. Finally, the band gap values increased from 3.32 to 3.33 eV with an increase in EDA-capping concentration; and decreased from 3.32 to 3.27 eV with an increase in the L-cyst.-capping concentration. The highly luminescent ZNRs composed of well-aligned and improved particle distributions with perfect crystallization produced at the 0.5 mM L-cyst.-capping, can be used as a possible photoanode for dye-sensitized solar cells.

Effective two-step chemical deposition for homogeneous lead sulfide thin films on a flexible polymer substrate

Chalcogenide PbS has been extensively studied as a p-type semiconductor material for various optoelectronic devices. Here, an effective two-step chemical bath deposition process is introduced to achieve dense microstructure of PbS thin films specifically for a flexible polyethylene terephthalate (PET) substrate. Three different types of substrates, such as Cu foils, glass substrate and PET, were initially examined to compare different crystal growth behaviors of PbS thin films depending on the choice of substrate. Only the PET substrate demonstrated an unacceptable coverage of films even with the extended deposition due to a retarded growth presumably with more scattered initial distribution of nuclei. Conclusively, two-step deposition processing at a low temperature of 40 °C for the PET substrate was successful in achieving homogeneous microstructures with proper bandgap and film thickness. As a promising result, the 60 min plus 60 min-double depositions at 40 °C produced an ideal bandgap of ~1.58 eV with a proper film thickness of ~200 nm.

Decorating (001) dominant anatase TiO2 nanoflakes array with uniform WO3 clusters for enhanced photoelectrochemical water decontamination

A facile two-step chemical bath deposition (CBD) method has been developed for the preparation of uniformly crystalline anatase WO3/TiO2 array on FTO substrate. The synthesis starts from the hydrothermal growth of TiO2 array in a homogenous HCl aqueous solution containing stabilized titanium isopropoxide, NH4F and acetylacetone (AcAc). Electron microscopy and the XRD analysis suggest the addition of AcAc chelating agent can facilitate the preferential growth of interconnected and vertically aligned anatase (001) facets. While (101) dominant TiO2 bipyramid array may form without AcAc. The subsequent decoration of WO3 clusters on TiO2 array is achieved by post-depositing TiO2 array in (NH4)2WO4 aqueous solution followed with a calcination at 450 °C, the resultant WO3/TiO2 array shows a significantly elevated photocurrent performances owing to the high separation efficiency of charge carriers. The enhanced photoelectrocatalytic properties are explained by the efficient charge carrier separation at the heterojunction between WO3 and TiO2. A faster photoelectrochemical degradation of methylene under simulated sunlight further demonstrates the potential usefulness of WO3/TiO2 arrayed photoelectrocatalyst in solar-driven environmental purification and solar fuel synthesis.

Electrical and Optoelectronic Properties of Chemically Prepared PbS/MnS Heterojunction

Lead sulfide (PbS)/manganese sulfide (MnS) heterojunction is synthesized by a simple two-step chemical bath deposition technique. The as-synthesized heterojunction is studied based on the optical and electrical analyses. The optical absorbance spectrum of the test structure confirms dual peaks at two different wavelengths, which has prompted consideration of the two band gaps of the structure. The origin of dual peaks in the absorbance plot is attributed to the existence of the PbS base layer and the MnS window layer. The band gaps are estimated using the conventional Tauc’s method (Eg = 1.75 eV and 2.9 eV) and also by the absorbance spectrum fitting method (Eg = 1.82 eV and 2.97 eV). In the dc analyses, the PbS/MnS heterojunction possesses low dark current and high dynamic resistance. However, under illumination (400–700 nm) a distinct photo-response is observed, showing a substantial rise in device current with the reduction of dynamic resistance. The photo-response of the heterojunction is examined at 635–699 nm, 514–538 nm and 410–452 nm wavelengths by analyzing the photo-current and photo-resistance. The device is found to be more photosensitive at lower wavelength illuminations compared to the higher wavelength exposures.

Facile synthesis of NiCo2S4 nanowire arrays on 3D graphene foam for high-performance electrochemical capacitors application

Herein, we report a facile two-step chemical bath deposition method for the preparation of NiCo2S4 nanowire arrays grown on three-dimensional graphene foams (3DGF) for advanced ECs. The porous structure of 3DGF can be used as an ideal scaffold for preparation of continuous fibrous composite electrodes and could avoid using the heavier metal collectors and binder. We realized a mixed dimensional heterostructure via direct synthesis of one-dimensional NiCo2S4 nanowires array on the seamlessly continuous spatial graphene foam, and further applied it as supercapacitor electrode materials. The unique nanowire arrays morphology results in an excellent property with a high specific capacitance of 1454.6 F g−1 (1.1 F cm−2) at 1.3 A g−1, remarkable rate performance and exceptional reversibility with a cycling efficiency of 96% after 3000 cycles at a high current density of 13 A g−1.

Enhanced photoelectrochemical response for hydrogen generation in self-assembled aligned ZnO/PbS core/shell nanorod arrays grown by chemical bath deposition

We have exploited low ion-flux promoting chemical conditions to create self-assembled ZnO/PbS core/shell aligned nanorod (NR) array architecture consisting of PbS shell on nano-crystal ZnO NRs and demonstrate exceedingly high photoelectrochemical (PEC) cell performance using two-step chemical bath deposition process. FESEM and HRTEM studies confirm the uniform conformal growth of 20 nm thick (200) PbS on hexagonal prismatic (002) ZnO NRs. A highest photocurrent density ∼13.6 mA/cm2 at +1.0 V vs Ag/AgCl under AM1.5 solar light illumination (photoconversion efficiency of 7% vs Ag/AgCl) is achieved for the first time, with the help of unique combination of improved nano-structure, high visible and NIR light absorption, and quenched photoluminescence. It is immensely important for enhanced water splitting capability for hydrogen generation. This remarkable high current density is interpreted in terms of linker free ion-by-ion growth and resulting uniform coverage of ZnO NRs by PbS shell, obtained by nucleation controlled deposition mechanism leading to defect-less abrupt ZnO/PbS p–n interface and improved type-II band alignment.

Optically driven random lasing in ZnO nanorods prepared by chemical bath deposition

In this paper, we report on room temperature UV lasing emission observed in a mirror-less ZnO sample prepared by two-step chemical bath deposition technique; a popular low cost method for making ZnO nanorods. We attribute the mechanism of the laser emission to coherent multiple light scattering between the nanorods within the illuminated area of excitation. Reduced threshold condition was observed for the nanorods having smallest crystallite size. Furthermore, the ability to maintain the number of modes at different excitation areas of the sample as well as at different pump powers suggests this method of growing the ZnO nanorods as a promising growth method for industry in developing high efficiency low cost random lasers for future integrated photonic devices.