Search

In the class typical layered metal chalcogenide family, tin selenide (SnSe) has been explored resolutely as one of the significant binary IV-VI compounds for a wide range of energy storage applications. Two dimensional hexagonal tin selenide nanosheets have been synthesized using a one-pot colloidal method and tested as active electrode for supercapacitors without using any binder. The as-prepared SnSe electrode exhibits a capacitance of 617.9 F/g at a scan rate of 2 mV/s with a good electrochemical stability due to efficient ion transport between electrolyte to active electrode and charge transport between electrode and current collector. The high energy density of 28.5 Wh/kg along with high cyclic stability is due to the morphology assisted electrochemical activity of the electrode. The results indicate that the assembly of binder-free electrode by the proposed facile synthesis route has a promising application in producing high-performance energy storage devices.

Перовскітний матеріал CH3NH3PbI3 продемонстрував відмінні оптоелектронні властивості для використання в сонячних елементах. Однак такі проблеми, як стабільність і несхожість у мобільності носіїв заряду, обмежують його застосування в сонячних елементах з об'ємним гетеропереходом (BHJ). Для підвищення стабільності та продуктивності сонячних елементів було докладено зусиль шляхом включення відповідного сполучного матеріалу в BHJ. Однак розчинність компонентів BHJ в одному розчині може створити проблеми при одностадійному синтезі BHJ. Тут ми звітуємо про нашу теоретичну та експериментальну роботу з отримання BHJ перовскіт : Indene C60-Bisadduct (ICBA) з використанням схеми мікроемульсії без поверхнево-активної речовини (SFME) циклогексан:ацетон:DMSO (CAD), яка може вирішити проблему розчинності компонентів BHJ в одному розчині. Критична початкова об'ємна частка ацетону є важливою для підтримки стабільності мікроемульсії залежно від її складу. За допомогою теоретичного моделювання ми вивчили динаміку випаровування SFME з діапазоном початкового об'єму ацетону, який може перевести SFME із нестабільного стану в стабільний. Було помічено, що залежно від початкової об'ємної частки ацетону та температури підкладки тонка плівка SFME на підкладці, що твердіє, може переходити через різні стани, пов'язані з її стабільністю. Це може мати помітний вплив на структурні та оптоелектронні властивості BHJ. Експериментальні дослідження підтвердили ці прогнози. Даний метод може відкрити новий шлях виготовлення BHJ перовскіт : органічний для оптимальної роботи в оптоелектронних пристроях. CH3NH3PbI3 perovskite material has shown excellent optoelectronic properties for its use in solar cells. However, issues like stability and dissimilarity in charge carrier mobility limits its applicability in Bulk Heterojunction (BHJ) solar cells. Efforts have been made by incorporating suitable conjoining material in BHJ to increase stability and performance of solar cells. However, the solubility of BHJ components in one solution may pose problems in the single-step synthesis of BHJ. Here, we report our theoretical and experimental work on preparing perovskite: Indene C60-Bisadduct (ICBA) BHJ using a Cyclohexane: Acetone: DMSO (CAD) Surfactant Free Microemulsion (SFME) scheme, which can solve the problem of the solubility of BHJ components in a single solution. A critical initial acetone volume fraction is essential to maintain the stability of the microemulsion depending on its composition. With the help of theoretical simulation, we studied evaporation dynamics of SFME with a range of initial acetone volume, which can take SFME from an unstable state to a stable one. It was observed that, depending on the initial acetone volume fraction and substrate temperature, the solidifying thin film of SFME on the substrate may transit through different states related to its stability. This can have marked effect on the structural and optoelectronic properties of BHJ. Experimental studies confirmed these predictions. This method can open a novel way of tailoring perovskite:organic BHJ for optimum performance in optoelectronic devices.

CdS films were deposited by CBD on a glass substrate by using CdI2 as a Cd+ source, thiourea as an S− source and NH4OH as the complexing agent. The effect of slow and rapid cooling on the films after thermal annealing was investigated in the present study. X-ray diffraction and Raman spectra of the films suggest that thermal annealing followed by slow cooling gives CdS with enhanced crystallinity and reduced strain and dislocation density as compared to the films where they were cooled rapidly after thermal annealing. The results were supported by scanning electron microscopy and UV–Vis absorption spectroscopy. Hall Effect measurement shows the lowest resistivity and highest mobility obtained in the case of a slowly cooled sample as compared to the rapidly cooled sample. Carrier concentration in the range of about 1011 (cm−3) was found, and all the samples of CdS were of n-type conductivity.

A complete solid state device with FTO/PANI/PTh/ZnO/Al assembly prepared by absolute wet chemical methods including chemical bath deposition (CBD), successive ionic layer adsorption and reaction (SILAR) and spin coating has been studied to investigate the effect of thickness of active PANI layer on device performance. Structural, morphological and chemical bond features have been investigated by using X-ray diffraction, Field Emission Scanning Electron Microscopy and Fourier Transform Infrared spectroscopy of the layers and are discussed herein. Effect of PANI thickness on current-voltage characteristic has been studied under dark and illumination (100 mW/cm2, AM 1.5G, 1 Sun) condition to know the solar cell performance.

Ternary bulk heterojunctions using a wide band gap polymer P3HT and a narrow band gap polymer PTB7 as donors and ICBA as acceptor have been fabricated using a novel dual-feed approach in an ultrasonic spray. The binary blend of two donor polymers in a BHJ formed by a conventional method in which the two donor polymers are mixed intimately in a common solvent may lead to unfavourable phase morphology due to unfavourable interaction between them and puts constraints on the composition of the polymer blend in the BHJ. The unfavourable interaction may cause severe molecular disorder leading to charge recombination trap site, and thereby decreases the device performance. In the new method proposed in this paper intimate mixing of two donor polymers is avoided, which removes the constraint on the fraction of second donor in the first. Moreover, it also results in better polymer ordering leading to significantly higher hole mobility compared to that achieved with conventional method. The steady state photoluminescence study depicts more efficient FRET in P3HT:PTB7 binary blend prepared with dual channel method as compared to that prepared with single channel mode. With this method, ternary BHJ can be prepared even with higher concentration of the third component to have maximum power absorption, without compromising its optoelectronic properties. Although the superior properties of BHJ formed with the new dual-feed method did not reflected in similar performance in device functioning, with better choice of the donors and acceptor and with more control on nanoscale morphology through selection of proper solvents the device performance may improve to acceptable level. This report opens a new way of BHJ preparation in ternary organic solar cell fabrication.

A comprehensive study regarding the effect of different solvent vapours on organolead halide perovskite properties is lacking. In the present work, the impact of exposing CH3NH3PbI3 films to the vapours of commonly available solvents has been studied. The interaction with perovskite has been correlated to solvent properties like dielectric constant, molecular dipole moment, Gutmann donor number and boiling point. Changes in the crystallinity, phase, optical absorption, morphologies at both nanometer and micrometer scale, functional groups and structures were studied using X-ray diffraction, UV-visible absorption, FE-SEM, FTIR and Raman spectroscopies. Among the aprotic solvents DMSO and DMF vapours deteriorate the crystallinity, phase, and optical, morphological and structural properties of the perovskite films in a very short time, but due to the difference in solvent property values acetone affects the perovskite properties differently. Polar protic 2-propanol and water vapours moderately affect the perovskite properties. However 2-propanol can solvate the organic cation CH3NH3+ more efficiently as compared to water and a considerable difference was found in the film properties especially the morphology at the nanoscale. Nonpolar chlorobenzene vapour minutely affects the perovskite morphology but toluene was found to enhance perovskite crystallinity. Solvent properties can be effectively used to interpret the coordination ability of a solvent. The present study can be immensely useful in understanding the effects of different solvent vapours and also their use for post-deposition processing (like solvent vapour annealing) to improve their properties.

To address the problem of operational stability in conventional design of Organic Solar Cells (OSC), inverted solar cell structures are being investigated extensively. Inverted solar cell structures with ZnO nano-rods array (NRA) as interfacial layer is attracting much attention due to beneficial role played by ZnO NRAs. It not only addresses the limitation on charge extraction due to limited charge mobility but also simultaneously it can provide high-mobility routes to the charge carriers to reach to the cathode electrode also. In this paper we report synthesis of inverted OSC with active layer infiltrated in the ZnO nanorods array using Ultrasonic Spray method and confirmed total infiltration. Performance enhancement has been observed by addition of a thin PCBM layer between the electron transport layer and the active layer. The improvement has been attributed to the improved charge collection efficiency due to presence of PCBM layer.

Surface coating of CdS nanoparticles over the ZnO nanorods have been performed by using simple successive ionic layer adsorption and reaction at room temperature. Initially, the seed/compact ZnO layer have been deposited via SILAR (successive ionic layer adsorption and reaction) on to fluorine doped tin oxide coated glass (FTO) substrate followed by synthesis of ZnO nanorods by chemical bath deposition method. The synthesized nano heterostructure was characterized by X-ray diffraction (XRD), UV–Vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and high resolution-transmission electron microscopy (HR-TEM) techniques. The photovoltaic performance of the cell was recorded with a conversion efficiency of 0.123% under 100 mW/cm 2 simulated sunlight at AM 1.5G conditions.

Organometallic halide perovskite based solar cells are considered as the foundation of future photovoltaic technology. In these types of solar cells, it has been emphasized that the bulk heterojunction active layer architecture may show superior performance than the bilayer active layer architecture due to the increase in the interfacial area by intermixing both donor and acceptor phases in the bulk heterojunction. Organometallic halide perovskite with suitable acceptor in bulk heterojunction architecture can be a promising active layer in perovskite solar cells. Conventionally, the perovskite and acceptor are mixed together in a single solvent before thin film formation. Though this offers a one-step synthesis way, limited solubility of perovskite and acceptor in single solvent puts major constraint on the formation of bulk heterojunction through one-step solution processable method. This paper describes a new way of one-step synthesis of bulk heterojunction using surfactant free microemulsion in slot die method, which removes the constraint of limited solubility of the two phases in a single solvent. Emulsion of DMSO (solvent for CH3NH3PbI3) and cyclohexane (solvent for PCBM) stabilized with acetone was used for making perovskite:fullerene bulk heterojunction. Solvent evaporation dynamics has been simulated to get deeper understanding of emulsion solidification leading to bulk heterojunction formation. Structural and optical studies support the formation of bulk heterojunction for efficient charge separation at donor:acceptor interfaces. A perovskite solar cell employing this bulk heterojunction has also been reported.

Controlled growth of different sizes of cadmium selenide (CdSe) nanoparticles over well aligned ZnO nanorods have been performed using successive ionic layer adsorption and reaction (SILAR) technique at room temperature (27 °C) in order to form nano heterostructure solar cells. Deposition of compact layer of zinc oxide (ZnO) by SILAR technique on fluorine doped tin oxide (FTO) coated glass substrate followed by growth of vertically aligned ZnO nanorods array using chemical bath deposition (CBD) at low temperature (100 °C). Different characterization techniques viz. X-ray diffractometer, UV-Vis spectrophotometer, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been used to know the structural, optical, morphological and compositional properties of synthesized nano heterostructure. The photovoltaic performance of the cells with variation in SILAR cycles for CdSe and with use of different electrolytes have been recorded as J-V characteristics and the maximum conversion efficiency of 0.63% have been attained with ferro/ferri cyanide electrolyte for 12 cycles CdSe coating over 1-D ZnO nanorods.

Simple and inexpensive wet chemical route, namely successive ionic layer adsorption and reaction (SILAR) is demonstrated to coat the inorganic semiconducting Bi 2 S 3 nanoparticles (NPs) at room temperature on chemical bath deposited vertically aligned ZnO nanorods (NRs). The films were characterized by X-ray diffraction (XRD), UV–vis spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), Raman spectroscopy and surface profiler in order to confirm the crystal structure, optical properties, surface morphology, elemental compositions and film thickness. Finally, the solar cell device was formed by using Bi 2 S 3 coated ZnO NRs as photoanode, liquid electrolyte as hole conducting media and platinum (Pt) as a back contact. The power conversion efficiency ( η ) of 0.025% under illumination of simulated sunlight (AM 1.5 G, 100 mW/cm 2 ) was observed.

Orientation of polar polymer chains can be achieved by direct application of high electric field to the polymer thin films. Changes in morphology due to such electric field treatment can impart changes in electrical conductivity of the thin films. PEDOT:PSS thin films exhibit isotropic in-plane electrical conductivity. We have observed that the electric field treatment at high temperature lead to anisotropic behaviour in in-plane conductivity of thin film of PEDOT:PSS film. In case of films prepared with aqueous solution of PEDOT:PSS, electric field treatment cause rise in electrical in-plane conductivity in orthogonal direction to electric field and it falls in direction of electric field. Thin films prepared with DMSO added aqueous solution of PEDOT:PSS show initial isotropic switching from high conductivity to low conductivity state due to electric field treatment. Prolonged treatment resulted in significant fall in in-plane electrical conductivity specifically in the direction of electric field. A model, based on re-orientation of polymer chains caused by interaction of electric field and electric dipoles of PEDOT:PSS chains, has been proposed to explain this behaviour. The hypothesis is supported by the results of Raman spectroscopy. Co-relating changes are also recorded in absorption spectra of these films. This study may find application in write once read many memory devices based on PEDOT:PSS.

In this report, the fabrication of a solar cell device with the structures FTO/PPy/PTh/ZnO/Al was performed using wet chemical synthesis methods in open environment. The cost-effective methods like CBD, SILAR, and spin coating have been used for the synthesis. The effect of thickness of PPy active layer on the device performance is investigated. Features such as structural, morphological, and chemical bonding of the layers have been investigated using X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy and are discussed herein. Effects of PPy thickness on current–voltage characteristics have been studied under dark and illumination at 1 Sun (100 mW/cm2, AM 1.5 G) condition to study the solar cell performance.

Recent improvements in electronic and optoelectronic devices based on solution processable polymers have motivated development of scalable processing techniques like Ultrasonic Spray technique. Including potential for roll to roll fabrication, it has many other strengths. However, with spray coating it can be difficult to prepare films with a smooth surface. Here, we present model for Ultrasonic Spray deposition of thin films, which establish a clear correlation between process parameters and the film formation process, which ultimately decide the structural features of the thin films. Based on the time to cover the spray deposition area by the sprayed droplets and the time for droplet evaporation, a balance parameter has been defined. It provides a mean to determine suitable process parameters for uniform film formation by Ultrasonic Spray method. The model is further modified for the region of higher solution flow rates, where non-uniformity in droplet distribution is introduced. The predictions based on the model have been experimentally verified with thin films of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid (PEDOT:PSS). The method presented here can be used to predict proper deposition parameters for smooth film deposition by Ultrasonic Spray technique. Finally, the effect of film morphology on the sheet resistance of thin films of PEDOT:PSS is also presented.

Hydrogenated amorphous silicon (a-Si:H) thin films were deposited from pure silane (SiH 4 ) using hot-wire chemical vapor deposition (HW-CVD) method. We have investigated the effect of substrate temperature on the structural, optical and electrical properties of these films. Deposition rates up to 15 A s −1 and photosensitivity ∼10 6 were achieved for device quality material. Raman spectroscopic analysis showed the increase of Rayleigh scattering in the films with increase in substrate temperature. The full width at half maximum of TO peak ( Γ TO ) and deviation in bond angle (Δ θ ) are found smaller than those obtained for P-CVD deposited a-Si:H films. The hydrogen content in the films was found

This paper presents ethanol vapour sensing properties of WO3 thick films. In this work, the WO3 thick films were prepared by standard screen-printing method. These films were characterized by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). The ethanol vapour sensing properties of these thick films were investigated at different operating temperatures and ethanol vapour concentrations. The WO3 thick films exhibit excellent ethanol vapour sensing properties with a maximum sensitivity of ∼1424.6% at 400°C in air atmosphere with fast response and recovery time.

The present investigation deals with the fabrication of liquid petroleum gas (LPG) sensor based on WO3. In this work, WO3 films were prepared by standard screen-printing method. These films were characterized by X-ray diffraction (XRD) measurements, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). These films exhibit high sensitivity, excellent selectivity, fast response and recovery to LPG at 400°C in air atmosphere.

Room temperature chemical bath deposition (CBD) method was employed to anchor CdSe quantum dots (QD׳s) on mesoporous TiO2, exclusively without using linkers. The sizes of CdSe QD׳s were tuned simply by varying the deposition time in CBD method and uniform coverage of CdSe QD׳s on mesoporous TiO2 was achieved. The chemical approach provided in the present investigation is free from the post annealing treatment after the growth of QD׳s; essential to lower down the process cost. The red shift in absorption maxima was observed with respect to deposition time in the UV–vis spectra which strongly supports the size quantization effect. Finally, the synthesized CdSe sensitized TiO2 has successfully demonstrated the potential ability as a quantum dot sensitizer for solar cell application when illuminated with 50 mW/cm2 intensity (air mass 1.5)., BRS is thankful to DAE-BRNS sanctioned major research (2010/37C/5/BRNS).

PEDOT: PSS (Poly (3, 4-ethylenedioxythiophene)): (Polystyrene sulfonate) is being widely explored as a buffer layer or charge collecting electrode in many optoelectronic devices. Good out-of-plane electrical conductivity of PEDOT: PSS is prime importance for application in optoelectronic devices such as organic solar cells and light emitting diodes. Enhanced out-of-plane electrical conductivity results in improved device performance. In this article we show an order of magnitude enhancement in out-of-plane electrical conductivity of PEDOT: PSS achieved through electric field treatment of PEDOT: PSS thin films kept at elevated temperature. This change in electrical behavior is due to conformational changes caused by interaction of applied electric field with electrical dipoles associated with the PEDOT: PSS chains. Upon adding DMSO in the PEDOT: PSS solution films show different behavior than when it was not added. Raman and absorption studies confirm the morphological variations induced due to applied electric field.

Hydrogenated amorphous silicon (a-Si:H) films were deposited using pure silane (SiH 4 ) without hydrogen dilution by hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical, and structural properties of these films are systematically studied as a function of process pressure ( P r ). The device quality a-Si:H films with a photosensitivity >10 5 were deposited at a deposition rate >40 A/s at low process pressure. However, a-Si:H films deposited at higher process pressures show degradation in their electrical and structural properties. The FTIR spectroscopic analysis showed that a-Si:H films deposited at low process pressure contain hydrogen mainly in mono-hydrogen (Si–H) configuration whereas films deposited at higher process pressure have hydrogen in di-hydrogen (Si–H 2 ) or poly hydrogen (SiH 2 ) n complexes. The hydrogen content ( C H ) in the films was found to be less than 4 at.% over the entire range of process pressure studied. This indicates that the growth of a-Si:H films is mainly from the atomic species (Si and H) evaporated from the hot filament and hydrogen gets incorporated in the film via gas-phase reactions and substrate–gas interactions. The band gap, however was found ∼1.71 eV or much higher. We attribute high band gap at low hydrogen content may be due to presence of microvoids. Raman spectroscopic analysis showed increase in structural disorder and Rayleigh scattering with increase in the process pressure.

Hydrogenated amorphous silicon (a-Si:H) films were deposited using pure saline (SiH 4 ) without hydrogen dilution by the hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical and structural properties of these films are systematically studied as a function of filament temperature ( T fil ). The device quality a-Si:H films which were obtained at high deposition rate (3≤ r d ≤85 A/s) using filament temperature (1400≤ T fil ≤1900 °C) without hydrogen dilution show good structural, optical and electrical properties. However, the films deposited at higher filament temperature show an amorphous-to-microcrystalline transition. The FTIR spectroscopic analysis showed that a-Si:H films deposited at low filament temperature contain hydrogen mainly in mono-hydride (Si–H) configuration whereas films deposited at higher filament temperature have hydrogen in di-hydride (Si–H 2 ) or poly-hydride (SiH 2 ) n complexes. The low hydrogen content ( C H ) in the films indicates that the growth of a-Si:H films is mainly from the atomic species (Si and H) evaporated from the hot filament and hydrogen is incorporated in the film via gas phase reactions and substrate–gas interactions. The band gap, however, was found to be ∼1.71 eV or much higher. We suggest high band gap at low hydrogen content may be due to the presence of microvoids. Raman spectroscopic analysis showed the increase in structural disorder and Rayleigh scattering with increase in filament temperature.

Hydrogenated amorphous silicon germanium (a-SiGe:H) films were deposited using SiH4 and GeH4 mixture without H dilution by hot wire chemical vapor deposition (HW-CVD) technique. The electrical, optical and structural of these films are systematically studied as a function of substrate temperature (Tsub). The FTIR spectroscopic studies showed that a-SiGe:H films deposited at high Tsub contain H mainly the monohydride configuration whereas the films deposited at low Tsub has H in polyhydrides or (Si–H2)n complexes form. The low CH in a-SiGe:H films indicates that the growth of film is mainly from the atomic species evaporated from the hot filament and H gets incorporated in the film via gas phase reactions and substrate–gas interactions. Raman spectroscopic studies showed that the structural order of a-SiGe:H films improve with increase in Tsub. The T sub =300 ° C was found to be the optimized substrate temperature for the synthesis of device quality a-SiGe:H films.

Multilayer structures of the type a-Si:H/μc-Si:H were fabricated for the first time by hot wire chemical vapor deposition (HW-CVD) technique. These multilayers were studied for their opto-electronic and photovoltaic properties as a function of a-Si:H sublayer thickness. The microcrystalline phase of a-Si (μc-Si:H) of thickness 250 A have been used to create drift field in these multilayer structures. The quantum size and photovoltaic effects are observed in these multilayer structures. The persistent photoconductivity measurements clearly indicate the existence of interface defects and spatial charge separation due to the formation of p-n junction field. The best photovoltaic performance was obtained with the fill factor 0.4062 and conversion efficiency ( η ) 2.08% over an active area of 0.0132 cm 2 . The advantage in these multilayer structures is that no hazardous gases are involved in the fabrication process because no intentional doping is performed and all depositions were carried out in a single deposition chamber.

The electrical, structural and optical properties of hydrogenated amorphous silicon (a-Si:H) films deposited from pure silane (SiH 4 ) using hot wire chemical vapor deposition (HW-CVD) technique are systematically studied as a function of silane flow rate F SiH 4 between 5 and 30 sccm. We found that the properties are greatly affected by the silane flow rate over the range we studied. The device quality a-Si:H films with a photosensitivity >10 5 were deposited by HW-CVD at a deposition rate >10 A s −1 using low silane flow rate. However, a-Si:H films deposited at higher silane flow rate and/or higher deposition rates show degradation in their structural and electrical properties. The FTIR studies indicate that the hydrogen bonding in a-Si:H films shifts from mono-hydrogen (Si–H) to di-hydrogen (Si–H 2 ) and (Si–H 2 ) n complexes when films were deposited at higher silane flow rate. The hydrogen content in the a-Si:H films increases with increase in silane flow rate and was found to be less than 10 at.%. The Raman spectra show increase in disorder and the Rayleigh scattering with increase in silane flow rate. The optical band gap also shows an increasing trend with silane flow rate. Therefore, only the hydrogen content cannot be accounted for the increase in the optical band gap. We think that the increase in the optical band gap may be due to the increase in the voids. These voids reduce the effective density of material and increase the average Si–Si distance, which is responsible for the increase in the band gap. Silane flow rate of 5 sccm, appears to be an optimum flow rate for the growth of mono-hydrogen (Si–H) bonded species having low hydrogen content (∼4.25 at%) in a-Si:H films at high deposition rate (∼12.5 A s −1 ), high photosensitivity (∼10 5 ) and small structural disorder.

In this letter, we report narrow band gap (1.39–1.53 eV) a-SiGe:H films with high photosensitivity (∼10 4 –10 5 ) are grown successfully by HW-CVD using a mixture of (GeH 4 +SiH 4 ) at low flow rates and without hydrogen dilution with higher deposition rates (>10 A/s). These films are characterized by Raman spectroscopy, FTIR spectroscopy and UV–Visible spectroscopy. The band gap of a-SiGe:H films can be narrowed by increasing the germane gas fraction without apparent degradation in their electronic properties. The low hydrogen content in a-SiGe:H films indicates that the growth of a-SiGe:H films is mainly from the atomic species (Si, Ge and H) evaporated from the hot filament.

Synthesis of monomorphic, SnS nanoparticles without using a capping agent is a difficult task with chemical route of synthesis. This paper reports on synthesis of tin monosulfide (SnS) nanopartilces with dimension in the quantum-dot regime using surfactant free microemulsion with single microemulsion scheme. This has been achieved by reaction in microreactors in the CME (C: chlorobenzene, M: methanol and E: ethylene glycol) microemulsion system. This is an easy and controllable chemical route for synthesis of SnS nanoparticles. Nanoparticle diameter showed prominent dependence on microemulsion concentration and marginal dependence on microemulsion temperature in the temperature range studied. The SnS nanoparticles formed with this method form stable dispersion in Tolune.

Titanium dioxide/bismuth trisulphide (TiO2/Bi2S3) heterostructures are synthesized in a linker free synthesis approach which consists of a facile spin coating method followed by a successive ionic layer adsorption and reaction (SILAR) at room temperature (27 °C). These TiO2/Bi2S3 thin films are characterized by using different techniques. X-ray diffraction and high resolution transmission electron microscopic studies confirm the formation of layered heterostructures. Surface morphological analysis confirmed the uniform coverage of tiny Bi2S3 particles on TiO2 surface. Further, quantum size effect is observed by using the optical absorption studies. Finally, sandwich type devices are constructed and photovoltaic parameters are investigated in the illumination of standard 1 sun condition [AM 1.5G, 50 mW/cm2] and the photovoltaic parameters are discussed herein. In addition to this the effect of different number of Bi2S3 SILAR cycles on photovoltaic parameters has been investigated., BRS is thankful to DAE-BRNS, Mumbai, India for the Major Research Project [Ref: 2010/37C/5/BRNS/830 dated 28/06/2010].

The electrical, structural and optical properties of undoped and phosphorus doped μc-Si:H films prepared by a HW-CVD technique have been studied. The hydrogen (H 2 ) dilution of silane has been varied carefully to produce undoped μc-Si:H films. The amorphous-to-microcrystalline transition was observed for a hydrogen dilution ratio >0.75. The phosphorus doped μc-Si:H films were deposited by varying the phosphine (PH 3 ) gas flow rate. The structural properties of these films have been investigated by Raman spectroscopy, low angle X-ray diffraction spectroscopy and Fourier transform infrared vibrational spectroscopy. Electrical characterization has been carried out by dark conductivity and charge carrier activation energy measurements. The phosphorus doped μc-Si:H films showed that the addition of PH 3 to the source gases promotes the growth of crystallinity. The increase in crystallite size and crystalline volume fraction with the addition of PH 3 to the source gases indicates that it enhances the crystallization of the μc-Si:H film. Low angle XRD studies shows that the PH 3 doped μc-Si:H does not show any preferential orientation crystallites. For optimized deposition conditions PH 3 doped μc-Si:H films with high dark conductivity (0.4 S/cm), low activation energy (0.03 eV) and high band gap (1.82 eV) were obtained with a high deposition rate (13 A/s). However, for these optimized conditions, the hydrogen content was relatively large (8.3 at.%).

Obtaining thickness uniformity over a large substrate area seems to be a bottleneck as far as the industrial applications of the hot-wire CVD (Cat-CVD) process is concerned. In order to address the different issues in this respect, we have simulated the hot-wire CVD growth process and proposed a proper filament geometry for maximum thickness uniformity. The hot filament was assumed as a one-dimensional assembly of point sources. Five types of commonly used filament geometries were considered for their performance to identify the best filament geometry for maximum thickness uniformity. Here, the chamber pressure was assumed to be low enough so that the Knudsen number Kn>1. Based on our results, we propose a parallel filament geometry for maximum thickness uniformity over large substrate areas. By applying the model further to the parallel filament geometry, the relations between substrate–filament distance and minimum filament length, as well as the number of parallel filaments and the separation between them, which are necessary for the required thickness uniformity over the given substrate area, were determined. The validity of the model was checked using the ‘Matched-Pair t-test’. The effect of chamber pressure on thickness uniformity and growth rate, when it is sufficiently high to make the Knudsen number Kn

Boron-doped hydrogenated microcrystalline silicon (μc-Si:H) films were prepared using hot-wire chemical vapor deposition (HWCVD) technique. Structural, electrical and optical properties of these thin films were systematically studied as a function of B2H6 gas (diborane) phase ratio (Variation in B2H6 gas phase ratio, dopant gas being diluted in hydrogen, affected the film properties through variation in doping level and hydrogen dilution). Characterization of these films from low angle X-ray diffraction and Raman spectroscopy revealed that the high conductive film consists of mixed phase of microcrystalline silicon embedded in an amorphous network. Even a small increase in hydrogen dilution showed marked effect on film microstructure. At the optimized deposition conditions, films with high dark conductivity (0.08 (Ω cm)−1) with low charge carrier activation energy (0.025 eV) and low optical absorption coefficient with high optical band gap (∼2.0 eV) were obtained. At these deposition conditions, however, the growth rate was small (6 A/s) and hydrogen content was large (9 at%).

Undoped a-SiGe : H films were deposited by the RF plasma chemical vapor deposition method. Films deposited at different substrate temperatures ranging between 100°C and 300°C were studied for their optoelectronic and structural properties. Structural defects like vacancies and microvoids were studied by positron lifetime spectroscopy (PLTS) at room temperature. Optoelectronic properties of the films were correlated with the PLTS measurements. The observations show a decrease in the deposition rate with substrate temperature. Good optoelectronic properties and proper structural relaxation have been obtained with a decrease in microvoid concentration.

The properties of a-SiGe:H films prepared by the glow discharge plasma CVD method at various interelectrode separation were studied systematically. This study was done at two different rf power densities. It has been found that interelectrode separation plays an important role in determining film properties. It shows a more marked effect on photosensitivity at lower rf power density than at higher rf power density. Photosensitivity, in general, decreased, whereas growth rate increased with the increase in interelectrode separation. High photosensitivity (1.3×105) was obtained even at higher growth rate (245 A/min) just by controlling the interelectrode separation. Bandgap of the films was about 1.4 eV. Structural properties of the films were studied by positron life time spectroscopy (PLTS).

Boron doped p-type hydrogenated microcrystalline silicon (μc-Si:H) films have been prepared by radio-frequency glow discharge method. Highly conductive p-type μc-Si:H films can be obtained even with lower concentration of hydrogen in the rf glow discharge plasma if chamber pressure is low. Effects of increase in hydrogen (H 2 ) flow rate and chamber pressure have been studied. The structural properties of the films have been studied by X-ray diffractometry. The electrical and optical characterization have been done by dark conductivity, Hall measurements and optical absorption measurements respectively. Film with conductivity 0.1(Ω-cm) −1 with band gap 2.1 eV has been obtained.

We describe the study of annealing after coating a TiOx film over P3HT:PCBM bulk heterojunction layer to improve the interface in order to improve the solar cell performance. We demonstrate that annealing after coating the TiOx interfacial film improves the interface between the bulk-heterojunction and TiOx layers and hence the device performance. However upon annealing the devices before coating the TiOx layer results in highly degraded performance. A systematic explanation of the improved device performance is

We here present a way of preparing the polymer: fullerene BHJ using dual feed method which can lead to formation of pure phases. In this report, we present results of our initial experiments in this direction. The effect of process parameters on the thickness and surface roughness of the active layer has been discussed. The structural and optical properties have been studied using the optical microscope, UV—visible spectroscopy and photoluminescence spectroscopy. Significant PL quenching indicates efficient charge separation in the BHJ formed using this technique. We have also compared the BHJ thin films prepared with this dual feed ultrasonic technique with the single feed spray method. The BHJ formed using this technique has been used as an active layer in OSC.

Bulk-heterojunction (BHJ) morphologies with pure domains and sharp interfaces can lead to a more pronounced photovoltaic performance in organic solar cells. In this paper we report the formation of bulk-heterojunction of P3KHT (poly [3-(sodium-6 hexanoate) thiophene-2, 5-diyl]) and PCBM (phenyl-C61-butyric acid methyl ester) using orthogonal solvents by the ultrasonic spray method, which can lead to pure phases and sharp interfaces. P3KHT and PCBM are soluble in water and chlorobenzene respectively, which are orthogonal solvents. The modelling and simulation of the ultrasonic spray method is reported, and shows the possibility of formation of interconnecting phases of the two components in P3KHT:PCBM BHJ, formed using orthogonal solvents, if specific process parameters are chosen. The modelling and simulation also presents a way to determine optimum parameter space in an intermittent spray deposition method using orthogonal solvents. P3KHT:PCBM BHJ has been prepared using three different approaches. Significant photoluminescence quenching, suggesting efficient excitons separation before recombination has been observed in BHJ prepared by the 'emulsion of solutions' method. The study of the optical properties of P3KHT:PCBM BHJ suggests that the BHJ may contain bilayer type structures embedded in the BHJ morphology, which is further confirmed by complementary experiments. This new approach to preparing BHJ with pure phase domains and sharp donor/acceptor interfaces may find applications in optoelectronic devices such as organic thin-film transistors, photodetectors, organic light emitting diodes and organic solar cells.

This paper presents acetone vapor sensing properties of WO(3) thick films. In this work, the WO(3) thick films were prepared by standard screen-printing method. These films were characterized by X-ray diffraction (XRD) measurements, and scanning electron microscopy (SEM). The acetone vapor sensing properties of these thick films were investigated at different operating temperature and acetone vapor concentrations. The WO(3) thick films exhibit excellent acetone vapor sensing properties with the maximum sensitivity approximately 456% at 300 degrees C in air atmosphere with fast response and recovery time.

In this paper, we explain why specific mixed solvent composition leads to appropriate film formation of composite (polymer: inorganic nanoparticle) during spin coating. As a typical case, P3HT:TiO2 film formation has been discussed by taking chloroform as good solvent for P3HT while ethanol, methanol, and 2-propanol are used as co-solvents for dispersing TiO2. Mixed solvent evaporation dynamics during film drying has been simulated to explain the experimental results. Present study can be immensely useful for selecting proper solvents and their initial ratio for blend film formation of a particular phase separation.

We demonstrate the use of controlling the ambient during spin coating to finely control the solvent evaporation rate in order to obtain varying degree of phase separation in P3HT:PCBM blend films and study the effect on device performance. To understand the basic phenomenon driving the phase separation, modelling study has been performed, which show that the phase separation is due to PCBM diffusion towards the nucleation site once its solubility limit is crossed during spin coating process.