Babasaheb R. Sankapal

Preparation and characterization of nanocrystalline CdSe thin films deposited by SILAR method

The successive ionic layer adsorption and reaction (SILAR) method has been used for the first time to deposit nanocrystalline CdSe thin film onto glass substrates. The SILAR method is a modified version of chemical bath deposition (CBD) method in a way that substrates are immersed in cations and anions alternatively and film growth takes place on the substrates. The preparative conditions such as concentration, pH, temperature, immersion time, immersion cycles, etc. are optimized to get nanocrystalline CdSe films. The films are characterized by high resolution transmission electron micrograph (HRTEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction, optical absorption and electrical resistivity measurements.

Electrical properties of air-stable, iodine-doped carbon-nanotube–polymer composites

We report the preparation and electrical characterization of air-stable, iodine-doped single-walled carbon nanotube (SWNT)–polymer composites, which show significant enhancement in electrical conductivity by a factor of 2–5 as compared to undoped SWNT-polymer composites. The analysis of temperature dependent conductivity data reveals that the conduction of iodine-doped SWNT composites can be well described by the thermal-fluctuation-induced tunneling model. The observed substantial conductivity enhancement in iodine-doped SWNT composites can be attributed to two factors: the higher conductivity of doped SWNTs and the smaller insulating polymer barriers between adjacent conductive SWNTs.

V 2 O 5 encapsulated MWCNTs in 2D surface architecture: Complete solid-state bendable highly stabilized energy efficient supercapacitor device

A simple and scalable approach has been reported for V2O5 encapsulation over interconnected multi-walled carbon nanotubes (MWCNTs) network using chemical bath deposition method. Chemically synthesized V2O5/MWCNTs electrode exhibited excellent charge-discharge capability with extraordinary cycling retention of 93% over 4000 cycles in liquid-electrolyte. Electrochemical investigations have been performed to evaluate the origin of capacitive behavior from dual contribution of surface-controlled and diffusion-controlled charge components. Furthermore, a complete flexible solid-state, flexible symmetric supercapacitor (FSS-SSC) device was assembled with V2O5/MWCNTs electrodes which yield remarkable values of specific power and energy densities along with enhanced cyclic stability over liquid configuration. As a practical demonstration, the constructed device was used to lit the ‘VNIT’ acronym assembled using 21 LED’s.

MoS2 ultrathin nanoflakes for high performance supercapacitors: room temperature chemical bath deposition (CBD)

Homogeneous ultrathin nanoflakes of MoS2 thin films have been successfully developed by simple and low cost room temperature chemical bath deposition (CBD) method which further applied as electrode material for high-performance supercapacitors. The surface morphological analysis revealed uniform growth of MoS2 nanoflakes on whole substrate surface. Structural analysis confirms the formation of rhombohedral crystal structure of MoS2. The electrochemical performances were tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance techniques. Different electrolytes were tested in order to find suitable electrolyte for MoS2 thin films. In addition, the effect of electrolyte concentrations on supercapacitive properties of MoS2 thin film was investigated. Thus, MoS2 ultrathin nanoflakes electrode exhibits excellent electrochemical performances with maximum specific capacitance of 576 F g−1 at 5 mV s−1 and good cycling stability of 82% over 3000 cycles.

Comparative studies on MWCNTs, Fe2O3 and Fe2O3/MWCNTs thin films towards supercapacitor application

An attempt has been made to synthesize multiwall carbon nanotubes (MWCNTs), Fe2O3, and Fe2O3/MWCNTs through a simple and cost-effective route onto a stainless steel (SS) substrate. The ‘dip and dry’ coating method was used for MWCNTs, whereas the successive ionic layer adsorption and reaction (SILAR) method was used for Fe2O3. Thin films were characterized using structural and surface morphological studies by XRD, FESEM and TEM. The results showed that hematite Fe2O3 nanoparticles with a particle size of less than 10 nm were uniformly coated onto the surface of MWCNTs. Comparative investigations have been made for MWCNTs, Fe2O3, and Fe2O3/MWCNTs as supercapacitive electrode materials with the aid of scan rate, cyclic voltammetry, charge–discharge studies, energy density, power density and stability. Among the three thin films, the Fe2O3/MWCNTs hybrid thin film electrode exhibited a high specific capacitance of 431 F g−1 at a scan rate of 5 mV s−1 and a high energy density of 38 W h kg−1 with a power density of 800 W kg−1 in 1 M Na2SO3 electrolyte solution. The detailed analyses are reported herein.

Anchoring cobalt oxide nanoparticles on to the surface multiwalled carbon nanotubes for improved supercapacitive performances

The present work explored a novel, simple and low cost ‘dipping and drying’ process followed by a successive ionic layer adsorption and reaction (SILAR) method for the synthesis of cobalt oxide anchored multiwalled carbon nanotubes (Co3O4/MWNTs). Initially, MWNTs have been coated on a stainless steel substrate by a simple ‘dip and dry’ method, on which further deposition of cobalt oxide nanoparticles was carried out by the SILAR method. Our results confirm the uniform coating of Co3O4 nanoparticles having sizes less than 15 nm on the surface of MWNTs. Later, the electrochemical performance shows that, the Co3O4/MWNTs films exhibit a maximum specific capacitance of 685 F g−1 in a 2 M KOH electrolyte at a scan rate of 5 mV s−1 with high cycle stability of 73% over 5000 cycles. Moreover, lower electrochemical equivalent series resistance (11.25 mΩ) give rise to the superior performance. These results show, the potential of Co3O4/MWNTs composite electrodes in electrochemical supercapacitors.

LPG sensor based on complete inorganic n-Bi2S3-p-CuSCN heterojunction synthesized by a simple chemical route

An effective and versatile room temperature soft chemical route was employed to deposit n-Bi2S3 films followed by p-CuSCN films onto fluorine doped tin oxide (FTO) coated glass substrates. Well optimized preparative parameters led to the formation of a good heterojunction between the n-Bi2S3 and p-CuSCN films without any post-annealing treatment. An interconnected microflake of CuSCN on to the nanocrystalline Bi2S3 film enables a high porous structure in the top layer. The device was completed by ensuring silver as a front and FTO as a back ohmic contact, and exposed to sense the liquefied petroleum gas (LPG) at room temperature (27 °C). The upper porous structure allowed enough room for the gas species to adsorb and de-adsorb easily at the interface. The device exhibited more than 70% response at 1370 ppm of LPG, and the process suggests the possibility to develop a room temperature LPG sensing device with a low cost chemical method.

Wet chemical synthesis of ZnO thin films and sensitization to light with N3 dye for solar cell application

Simple wet chemical synthesis of ZnO thin films has been carried out at room temperature (27 °C) from an aqueous alkaline bath followed by annealing in air at 100 °C on fluorine doped tin oxide coated glass substrates. The deposited film showed an optical band gap of 3.28 eV with a thickness of about 40 µm with a hexagonal crystal structure. A flower-like surface morphology consisting of petals was observed. These petals are made up of a fibrous network with interconnected nanoparticles leading to a high surface area. This obliged us to use this structure for dye-sensitized solar cells with lower fabrication process cost than conventional high temperature sintered methods which are commonly used for ZnO and TiO2. It would be advantageous to use a flexible plastic substrate instead of routine glass in future. ZnO showed a current conversion efficiency (η) of 0.34% with chemically adsorbed N3 dye at standard AM 1.5 condition with illumination of light intensity 100 mW cm−2.

Analysis of Zinc Compound Buffer Layers in Cu(In, Ga)(S, Se) 2 Thin Film Solar Cells by Synchrotron-Based Soft X-Ray Spectroscopy

Zinc-based buffer layers like ZnSe, ZnS, or wet-chemically deposited ZnO on Cu(In, Ga)(S, Se) 2 absorber materials (CIGSSe) have yielded thin film solar cell efficiencies comparable to or even higher than standard CdS/CIGSSe cells. However, little is known about surface and interface properties of these novel buffer layers. In this contribution we characterize the specific chemical environment at the absorber/buffer-interface using X-ray Emission Spectroscopy (XES) and Photoelectron Spectroscopy (PES) in a complementary way. Evidence of intermixing and chemical reactions is found for different buffer materials and deposition methods.

One-dimensional cadmium hydroxide nanowires towards electrochemical supercapacitor

Cadmium hydroxide [Cd(OH)2] nanowires have been successfully synthesized by a simple chemical bath deposition method (CBD) on a stainless-steel (SS) substrate. By scanning electron microscopy (SEM), the surface architecture displays the formation of bundles of high-surface-area nanowires (NWs), which are beneficial for supercapacitor applications. Cd(OH)2 NWs on SS has been tested as an electrode material for supercapacitor applications via electrochemical studies by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy techniques in an aqueous electrolyte. Electrochemical data confirm that Cd(OH)2 NWs thin-film electrode exhibits supercapacitor behavior, having a yield of 267 F g−1 specific capacitance at 5 mV s−1 scan rate with excellent cycling life (86% capacitance retention over 1000 cycles). A Cd(OH)2/Cd(OH)2 symmetric supercapacitor device provides a maximum energy density of 11.09 W h kg−1 and a power density of 799 W kg−1 at a current density of 0.84 A g−1. The present work demonstrates that Cd(OH)2 NWs thin film is a promising, low-cost alternative material prepared by a simple, binder-free chemical bath deposition method (CBD) for supercapacitor applications.