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Lead halide perovskite (CsPbBr3) quantum dots (QDs) and two-dimensional (2D) layered transition metal dichalcogenides have a significant application in solution-processed optoelectronic devices.

During the winter (Rabi) season of 2019-20, the experiment was conducted in a farmer's field in the village of Loharapur, Varanasi, to investigate the impact of nutrient management technologies in alluvial soil with farmyard manure and various levels of inorganic fertilizers under mustard (Brassica juncea L.). Based on the STCR target yield idea, the use of plant nutrients has achieved mustard (18.0 q ha-1) and (22.0 q ha-1) outputs (soil test crop response technology). The test results indicated that the target yields were reached within + 5% of site modifications, confirming the validity of the formulae used to prescribe integrated mortar fertilizer dosages. For RDF, the highest production increases of 22 q ha-1 (37, 60%), followed by 18 q ha-1 were recorded (12.05 percent). The maximum cost-effectiveness and profit rate of 22.00 q ha-1 was the result. Organic carbon content is positive and significantly connected to the activity of the enzyme. As a consequence, the combination of NPK and FYM has been more successful in improving the productivity of rice aimed at 18 q ha-1, 22 q ha-1, and soil nutritional status than a single application of FYM or chemical fertilizer. Significant net benefits of mustard at the site (Rs 55,190.00 and Rs 38,583.00) in the treatment of plant nutrient levels in the soil test; (STCR treatment). Though fertilization enhanced mustard production above control, it was reported that using NPK and FYM together was more successful than using them alone in increasing mustard productivity.

Titanium diselenide (TiSe2) is the least studied member of the transition metal dichalcogenide family due to a lack of available synthesis methodology, controlled bandgap engineering, and rapid characterization of layers. In this paper, we report the chemical exfoliation of TiSe2 platelets synthesized by the chemical vapor transport route in ortho-dichlorobenzene (o-DCB) functionalized with oleylamine (OLA), for the first time to the best of our knowledge. It is found that the addition of OLA supports the formation of a stable dispersion of a large area of the TiSe2 sheets due to surface capping with the OLA molecules indicating the importance of the ligand in dispersion behavior. The X-ray diffraction pattern confirms the hexagonal structure of the TiSe2 platelets with the space group P3[combining macron]m1 while Raman spectroscopy reveals that two modes of vibration i.e. A1g and E2g exist with layered structures having dimensions in micrometers as confirmed by scanning electron microscopy. Fourier transform infrared spectroscopy confirms the successful functionalization of chemically exfoliated TiSe2 nanosheets. Field-emission scanning electron microscopy reveals that exfoliated TiSe2 has a thickness of 15-55 nm whereas high-resolution transmission electron microscopy indicates thicker sheets for ligand-free exfoliated TiSe2 which are crystalline. Atomic force microscopy confirms the formation of nanosheets. UV-Visible, photoluminescence, and time-resolved PL spectroscopy showed an enhanced effect and better average lifetime of excitation for the exfoliated sheets with OLA than those without OLA. The C-V studies reveal that with increasing scan rate, the corresponding current also increases. The present study offers the possibility of their utilization in optoelectronics, advanced low-power electronics, voltage-controlled oscillators, ultra-fast electronics, and electrochemical devices.

We report the fabrication and characterization of varying concentration (x) of copper (Cu)-doped TiO2 nanocomposites [Cu( x )TiO2(1- x )] exploring the photocatalytic properties for sunscreen appli...

Ternary bismuth halides are interesting functional materials closely related to Pb halide perovskite photovoltaic material, and are widely sought after due to reduced toxicity of Bi compared to Pb. There are several reports on synthesis of Cs3Bi2Br9 nanocrystals (NCs) due to its being relatively stable compared to lead perovskite. Cs3Bi2Br9 nanocrystals have been synthesised using benzoyl bromide as an precursor using hot injection process at two different temperatures of 120 °C and 160 °C. Samples have been characterized for its structural, optical, microstructural and luminescent properties using X-ray diffraction, (XRD) UV-Vis spectroscopy, high resolution transmission electron microscopy and photoluminescent spectroscopy. XRD showed formation of Cs3Bi2Br9 phase with mono-crystalline structure. UV-Vis showed two types of band gap in the visible region which shows that the material can be used for photovoltaic applications. HRTEM confined the particles to be composed of nanocrystals with ˜5 nm particles in the samples grown at 120 °C and it the particles joined together yield various structures composed of nanoparticles. The time resolved photoluminescence shows average life times of 3.067 ns and 4.761 ns for samples grown at two different temperatures. To the best of our knowledge, this is the first report where benzoyl halide has been used as alternative precursor for the synthesis of lead free double perovskite Cs3Bi2Br9 nanocrystals which have many applications.

Synthesis of titanium dioxide nanoparticles (TiO2 NPs) has been done by sol-gel-hydrothermal colloidal route in two different apparatus; one being simple stainless steel (named as TiO2-B) and other...

We report the synthesis and characterisation of pristine and chromium (Cr) metal ion-doped titanium dioxide nanoparticles [Cr(x)TiO2(1−x)] to study the anomalous effect of Cr doping on the photocatalytic property of TiO2. The presence of dopants generates more number of recombination pairs and increases surface coverage sites which decreases photocatalytic activity. We study the structural morphology of the synthesised Cr(x)TiO2(1−x) samples using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. The effect of Cr3+ ions on the optical properties of TiO2 has been studied using various imaging and spectroscopic techniques. Further, the effect of doping of Cr on the photocatalytic activity of TiO2 has been analysed in detail. The concentration of Cr in TiO2 has been chosen as 0, 1, 5 and 10% by weight. It has been observed that the pristine TiO2 exhibits better photocatalytic activity as compared to Cr-doped TiO2 irrespective of the Cr concentration. This can be attributed to the fact that due to Cr doping in TiO2, the number of available adsorption sites for malachite green reduces which degrades its photocatalytic activity. It is also confirmed by photoluminescence (PL) and time-resolved photoluminescence spectroscopy. PL intensity increases, and lifetime decreases with increase in doping concentration. Radiative recombination of electron and hole pairs of Cr3+ in TiO2 degrades its photocatalytic activity. The degradation efficiency is found to be 96% in the case of pristine TiO2 which reduces to 12% when doped with x = 10% concentration of chromium. Therefore, it is observed that in comparison with Cr-doped TiO2, pristine TiO2 exhibits an improved photocatalytic activity which shows the anomalous effect of Cr doping on the photocatalytic property of TiO2.

The opto-electrical and magnetic field effects on cobalt phthalocyanine (CoPc) thin film single layer device were explored. The root mean square roughness of thin film was 5.8 nm. The mobility was estimated for space charge limited current region in the current–voltage characteristics. Magnetic field effect on injection current was studied in terms of organic magneto-conductance. The negative magneto-conductance (MC) was observed in CoPc thin film diode at different bias voltages. The negative values of MC were found to be 10.05, 8.29, 6.84, 4.98 and 3.13% for applied bias voltages 1, 2, 3, 4 and 5 V, respectively. The CoPc thin film absorbed the UV–visible wavelength range which were represented by two bands of CoPc molecule, B band and Q band. MC study of device under dark and light reveals the formation of trap assisted bipolarons and their quenching by the formation of photogenerated excitons. The device was checked for the resistive and capacitive behaviour by impedance spectroscopy. The contact resistance is approximately constant ~ 66 Ω at all applied bias voltages. The bulk and interface resistance vary from 1.8 to 0.6 kΩ and 50.06 to 1.43 kΩ, respectively. Similarly, the bulk and interface capacitance vary from 55.81 to 10.56 nF and 50.47 to 558.09 nF, respectively for applied bias voltages.

Erbium (Er3+) and ytterbium (Yb3+) co-doped ZnO upconversion (UC) nanoparticles based phosphors are synthesized by solution-combustion method. These UC phosphors are shown a strong UC emissions at red, green and blue wavelengths with the excitation of 980 nm diode laser source. To understand the influence of ZnO:Er3+-Yb3+ UC based nanoparticles on the performance of dye sensitized solar cells (DSSCs), the UC nanoparticles are incorporated into scattering layer of titanium dioxide films in the form of composite photoanode. The power conversion efficiency (PCE) of the DSSCs is increased from 8.34 to 8.72% after incorporation of ZnO:Er3+-Yb3+ upconverting nanoparticles. This enhancement in the PCE is due to increase in the short circuit current density (JSC) of 18.66 mA cm−2. The enhancement in the Jsc is due to the infrared light harvesting from infrared into the visible region, while the PCE of reference DSSC (without up conversion layer) is obtained 8.34% with the JSC of 17.89 mA cm−2.

Quaternary elements kesterite nanoparticles in pure kesterite phase were synthesized using solvothermal process with different zinc precursors. Secondary phase formations were observed if zinc acetate or zinc nitrate was used as the precursor. Synthesis of the pure kesterite phase was possible only by using of chlorides of copper (I), tin (II) and zinc and thiourea as the precursors, with ethylene glycol as the solvent. The average size of the kesterite nanoparticle was observed ∼3 nm with a band gap of 1.51 eV. EDX was used to confirm the stoichiometric composition of the nanoparticle. These nanoparticles were used as the counter electrodes in dye-sensitized solar cells and a power conversion efficiency of 7.12% under AM 1.5G illumination was obtained. Kesterite nanoparticle layer can therefore, be used as an alternate counter electrode in the dye-sensitized solar cell to replace costly and rare earth platinum counter electrode.

Bifacial dye sensitized solar cells (DSSCs) show potential for use in diffuse and low light environments, but their photoanode light scattering properties have not been optimised. We examine DSSC photoanodes composed of a mixed scattering layer (made by blend of 18NR-T and WER2-O pastes), sandwiched between nanostructured TiO2 layers (made by 18NR-T paste). WER2-O paste was chossen after accessing scattering properties: scattering coefficient (S), forward scattering ratio (FSR) and forward path length enhancement (FPLE) of the solid TiO2 particles of different shapes and sizes. Monte Carlo simulations of light harvesting indicate the optimal volume fraction of scattering particles ( f vsca ) in the sandwiched layer to be 5–30%. The proposed photoanode absorbs light effectively and the DSSC with scattering layer made by blend of 60% of 18NR-T and 40% of WER2-O paste showed the power conversion efficiency (PEC) of 8.54% and 5.26%, when illuminated from photoanode (PA) and counter electrode (CE) side, respectively. The effective sorting criteria and optimization routine used in this work can also be used for other devices like perovskite solar cells.

Kesterite (Cu2ZnSnS4) thin films are spray deposited under 0 V and 1500 V DC voltages and then treated with N2+H2S(5%) environment at 500 °C for 1 h for sulphurisation. The improvement in different properties like structural, optical, morphological and electrical occur in the kesterite films deposited under the electric field. The activation energy is also reduced for these films, after applying the DC voltage during the spray deposition. These improvements resulted in the enhancement of the catalytic properties of kesterite films for use as the counter electrodes in dye sensitized solar cells. Dye sensitized solar cell using the kesterite film as a counter electrode deposit under the applied voltage of 1500 V exhibits the power conversion efficiency of 4.93%, which is higher than that for the kesterite film deposit under the applied voltage = 0 V (3.77%). The power conversion efficiency of sulphurised kesterite films deposit at 0 V and 1500 V yield further improvement in the power conversion efficiency (6.58 and 7.67%, respectively).

The role of the surface plasmon resonance (SPR) of gold nanorods (Au NRs) on the performance of Y123 dye-sensitized solar cells (DSSC) was investigated. DSSCs were fabricated by incorporating different concentrations (0.6 to 3.0 wt%) of Au NRs into TiO2 photoanodes. With an increase in the concentration of the Au NRs, the light absorption by the Y123 dye loaded photoanodes enhanced linearly, but the charge extraction was susceptible to the concentration of the Au NRs. With optimized concentrations (∼1.8 wt%) of the Au NRs, the photocurrent of the DSSC enhanced from 12.45 to 15.74 mA cm-2, and the power conversion efficiency (PCE) improved from 5.31 to 8.86%. The DSSC performance was also verified using Au nanoparticles (the PCE was enhanced from 5.31 to 7.72%) for comparison with the Au NR DSSC performance, which demonstrated the advantage of the Au NRs' shape effect with longitudinal SPR due to the modified light interaction. To explain the experimental observations of the plasmonic DSSC, the Au NRs' extinction efficiency and spatial distribution of the near-fields in complete and porous TiO2 media were also estimated using the finite-element method.

The present study focuses on the impacts of annealing temperature in different ambiances on the morphological behavior and thin-film quality of CZTS nanoparticles. CZTS nanoparticles have been synthesized via the hot-injection colloidal route method. CZTS nanoparticles have been annealed in air, vacuum atmosphere, and sulphur environment (N2 + H2S(5%), respectively at 450 °C for 30 min. The structural, morphological, compositional, and optical properties of all CZTS thin films were analyzed. The volume fraction is increased in the vacuum annealed thin film keeping crystallite size as same as in the as-deposited film. This results in a reduction of cracks and voids and thus the surface defects of the vacuum annealed thin film as confirmed by scanning electron microscope (SEM). AFM also confirms the improved quality of CZTS thin film annealed in a vacuum. PL curves also confirm the minimum defects in the case of vacuum-annealed thin films. Thus, the study reveals that the best quality CZTS thin films i.e. films with the least pinholes, cracks, and voids without any significant change from the initial conditions can be obtained after annealing in the vacuum environment.

Sputter deposition of multilayer ZAZ (ZnO/Ag/ZnO) and AAA (AZO/Ag/AZO) TCO coatings has been done using a magnetron sputtering system. The deposition has been performed by moving the substrate under the desired target (ZnO or AZO and Ag) using a movable arm. This movable arm allows the substrate movement in the required order through a controller in a forward or reverse direction. Using this arrangement, the fabrication of ZAZ and AAA multilayer TCOs has been done on glass substrates at room temperature and the layer properties are found to be comparable with the properties of commercial ITO film. The fabricated ZAZ and AAA multilayers (with thickness around 70 nm) exhibit better electrical properties as compared to the commercial ITO film. The electrical resistivities of the ZAZ 2 and AAA 2 layers are 3.78 × 10−5 and 3.71 × 10−5 Ω cm, respectively which are much lower than the ITO resistivity of 4.56 × 10−4 Ω cm. The sheet resistances of ZAZ 2, AAA 2 and commercial ITO layers are 5.4, 5.3 and 16.8 Ω/□, respectively. The figure of merit (FoM) for AAA 2 multilayer is 45.5 × 10−3 Ω−1, much higher than commercial ITO film (23.7 × 10−3 Ω−1). The high-temperature annealing shows almost stable optical and electrical properties of the fabricated TCO layers up to 200 °C. Therefore, these TCOs can be used as electrodes for the solar cell fabrication where high-temperature annealing is required.

Europium doped TiO2 (TiO2:Eu3+) down-shifting (DS) nanophosphors (NPrs) were synthesized by the solution-combustion method with different concentrations of Eu3+. The X-ray diffraction results confirmed the formation of a polycrystalline tetragonal structure of the TiO2. The emission of colour of the TiO2:Eu3+ DS NPr was tuned by varying the doping concentration of Eu3+. The photoluminescence results confirmed that the TiO2:Eu3+ DS NPrs converted the UV light into visible light by energy down-conversion process, i.e. down-shifting of high energy UV photons to low energy visible photons. These TiO2:Eu3+ DS NPrs were used to enhance the efficiency of the Dye sensitized solar cell from 8.32% to 8.80%.

Ternary bismuth halides are interesting functional materials closely related to Pb halide perovskite photovoltaic material, and are widely sought after due to reduced toxicity of Bi compared to Pb. There are several reports on synthesis of Cs₃Bi₂Br

© 2019 International Solar Energy Society In this work, the scalable screen printing process has been adopted to prepare low-cost and earth-abundant tin selenide (SnSe) films to study as the counter electrode in dye-sensitized solar cells (DSSCs). The SnSe powder was synthesized by solid state reaction method and corresponding films were fabricated by screen printing technique. The electrocatalytic activity of SnSe for redox iodide/triiodide (I−/I3−) couple and charge transfer resistance at the CE/electrolyte interface were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The DSSC with SnSe counter electrode exhibited with power conversion efficiency (PCE) of ~5.76% with open-circuit voltage of 0.63 V and short circuit current density of 12.39 mA/cm2 whereas the DSSC with platinum counter electrode showed PCE of 8.09% with open-circuit voltage of 0.68 V and short circuit current density of 14.77 mA/cm2. Thus, earth abundant and low cost SnSe films fabricated by screen printing technique could be an alternative to costly platinum counter electrode in DSSC.

Made available in DSpace on 2019-10-06T15:21:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-02-15 Council for Scientific and Industrial Research University Grants Commission- Nepal Developing molecular self-assembly is an important step to generate ordered nanostructure materials. In this pursuit, a simple template-free method is reported to develop anisotropic nanostructures using metallopolymer precursors. The phenanthroline-based ruthenium complex monomer (PDAR) and its polymers [3-armed PPDAR (PPDAR-3) and 4-armed PPDAR (PPDAR-4)] were synthesized using ATRP method. These materials displayed higher glass transition temperatures (182 °C for PPDAR-4 and 176 °C for PPDAR-3) compared to the linear polymer, PPDAR (144 °C). The materials showed metal-to-ligand charge transfer (MLCT) absorption peak at 440 nm and armed polymers exhibited higher molar absorption coefficient (PPDAR-4: 7.6 × 105 M−1 cm−1 and PPDAR-3: 6.58 × 105 M−1cm−1) compared to the linear polymer (4.6 × 105 M−1cm−1). The materials were self-assembled in the presence of non-polar solvents to form uniform nano-domain micelles. Thin films of these materials were formed and subjected to elevated annealing temperatures (180 °C) and were fully characterized by AFM, SEM, and XRD techniques to understand the mechanism of self-assembly. Furthermore, dye sensitized solar cell (DSSC) devices were fabricated using the materials as additional components of a liquid electrolyte (I3 −/I−) to explore the role of these architectures on open circuit voltage (VOC) as well as cell power conversion efficiency (PCE). Overall, this study provides new insights in the area of metallopolymers. Polymers and Functional Materials Fluoro and Agrochemicals Department and Academy of Scientific & Innovative Research (AcSIR) CSIR-Indian Institute of Chemical Technology, Uppal Road CNRS ICMCB Univ. Bordeaux UMR 5026 CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road Institute of Chemistry São Paulo State University UNESP School of Physical Sciences Banasthali University, P.O. Banasthali Vidyapith Photovolatic Lab Centre for Energy Studies Indian Institute of Technology Delhi, Hauz Khas School of Chemical and Biomolecular Engineering The University of Sydney Polymer Engineering Division Soniya College of Pharmacy Institute of Chemistry São Paulo State University UNESP

© 2019 Elsevier B.V. The graphene oxide paste (GO) was prepared by mixing α-terpineol and ethyl cellulose, and GO films was prepared by screen printing on fluorine doped Tin oxide (FTO) glass substrates to validate as an alternative counter electrode material to platinum in dye sensitized solar cells (DSSC). The graphene oxide films were characterised by X-Ray Diffraction, Scanning Electron Microscopy, Raman spectroscopy and the catalytic properties of films were being investigated by cyclic voltammetry and electrochemical Impedance measurements. The DSSC fabricated by coupling TiO 2 films soaked in N719 dye with GO as counter electrode exhibited photoconversion efficiency of 5.58% under standard one Sun illumination, whereas platinum based device showed photoconversion efficiency of 7.57%. The present study suggests that graphene oxide counter electrodes can be considered as a promising alternative to platinum, with further optimisation, which clearly has advantages in terms of its abundance and low cost processing towards industrial prospects.

Spray deposition of molybdenum trioxide (MoO 3 ) hole transport layer under a DC voltage (500 V and 1000 V) applied to the nozzle yielded orthorhombic phase of MoO 3 (α-MoO 3 ) with no other phases present. The films had uniform, compact surface morphology with reduced roughness, increased transmittance and band gap as compared to those for spray deposited MoO 3 layer deposited without applying the DC voltage. In addition an increase in the work function was also observed possibly due to the change in the nanostructures formed on the surface. XPS result showed that the application of DC voltage during spray deposition reduced the oxygen vacancies. The reduced potential barrier height between MoO 3 and P3HT layer can be useful in organic bulk-heterojunction solar cell (ITO/MoO 3 /P3HT:PCBM/Al). This was indeed proven by organic bulk-heterojunction solar cell fabricated using the electric field assisted spray deposited MoO 3 layer yielding 2.71% power conversion efficiency with short circuit current density (J SC ) of 10.0 mA cm −2 , open circuit voltage (V OC ) of 0.57 V and fill factor (FF) of 47.4%. The organic solar cell fabricated using electric field assisted spray deposited MoO 3 layer showed an improved performance as compared to the standard spin coated solar cell.

Spray process is used for the deposition of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film under different voltages (0 V, 300 V, 500 V and 700 V) applied to the nozzle. The presence of the electric field during the spray process makes the P3HT:PCBM film smoother, uniform and more crystalline with well aligned domains. X-ray photoelectron spectroscopy study shows that PCBM rich surface is formed by application of the DC voltage (700 V) which improves the electron transport at the active layer and cathode interface. The application of electric field reduces the recombination at interfaces. The increased charge carrier separation between donor and acceptor at the interface and the crystallinity enhancement result in improved short circuit current density–voltage characteristics of Indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)/P3HT:PCBM/Aluminum solar cell. The organic bulk-heterojunction solar cell using the electric field assisted spray deposited PEDOT:PSS and P3HT:PCBM layers exhibited 84% and 154% increment in the short circuit current density and power conversion efficiency, respectively in comparison to the solar cell having spray deposited PEDOT:PSS and P3HT:PCBM layers in the absence of the electric field.

Spray technique is used for the deposition of Cu2ZnSnS4 (CZTS) films, taking the chlorides of Cu(I), Zn and Sn(II) along with thiourea as precursors for the spray solution, with the substrate temperature varying from 200 °C to 450 °C. Use of these precursors results in CZTS phase formation starting at 200 °C and only beyond 350 °C the secondary phases are formed. CZTS films deposited at 200 °C and 250 °C show high resistivity’s of 502.39 Ω-cm and 51.84 Ω-cm, respectively and carrier concentrations of 2.85 × 1014 cm−3 and 5.55 × 1015 cm−3, respectively. The formation of secondary phases at 400 °C and 450 °C strongly affects the film properties. CZTS films deposited at 350 °C show the best resistivity of 0.19 Ω-cm. SEM analysis shows growth of nano-flakes on the surface of the film deposited at 350 °C, and C-AFM reveals that the film has the highest current range due to high internal conductivity which can be the cause of reduced film resistivity and enhanced optical absorption. CZTS film at 350 °C had the lowest activation energy calculated from the Arrhenius plot of ln σ vs 1000/T. Energy dispersive spectroscopy (EDS) analysis shows that the atomic percentages of the constituents in the CZTS films change with the temperature and accordingly affect the band gap. The film deposited at 350 °C is nearly stoichiometric with the band gap of 1.45 eV making it best suited for solar cell fabrication.

Indium-doped zinc oxide (IZO) thin films were deposited on a glass substrate using spray technique with a direct current (DC) voltage applied to the nozzle to create an electric field during deposition. It was found that the presence of the electric field has a strong effect on doping efficiency, structural, electrical, and optical properties. Incorporation of indium in ZnO was confirmed by the Rutherford back scattering and X-ray diffraction peak analysis. Scanning electron microscope micrograph showed that the surface morphology changed from rice-like structure to flower-like compact structure. The electrical resistivity of IZO film prepared under the electric field was 2 × 10−3 Ω cm, transmission in the visible region was more than about 80%, and figure of merit (ΦTC) was 3.39 × 10−3 Ω−1. The films deposited under the electric field showed a band gap narrowing, which is explained using the many body effects in the perturbation theory. Spray deposited IZO film under the electric field was shown to be useful for making self-cleaning top glass in solar cell module fabrication. Copyright © 2015 John Wiley & Sons, Ltd.

This chapter consists of the detailed description for the deposition of gold nanoparticles with different sizes using electric field-assisted spray process (applied voltages to the nozzle are 0 V, 500 V, and 1 kV, respectively) for investigating their performance in inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag). Application of DC voltage during deposition resulted in a reduced size (35 nm as compared to 70 nm without DC voltage) of the nanoparticles (NPs) with more uniform coverage. The photovoltaic parameters of plasmonic solar cells with spray-deposited Au and ZnO layers (both at 1 kV) showed an improved power conversion efficiency (PCE). The absorption spectra and incident photon to current conversion efficiency (IPCE) curve indicate that the increased plasmonic broadband light absorption by using Au NPs provides enhancement of J SC . A maximum PCE of 3.6% is resulted for the solar cell with high short-circuit current density of ~15 mA cm−2.

Stoichiometric thin films of Cu2ZnSnS4 (CZTS) were deposited by the spray technique on a FTO coated glass substrate, with post-annealing in a H2S environment to improve the film properties. CZTS films were used as a counter electrode (CE) in Dye-Sensitized Solar Cells (DSCs) with N719 dye and an iodine electrolyte. The DSC of 0.25 cm(2) area using a CE of CZTS film annealed in a H2S environment under AM 1.5G illumination (100 mW cm(-2)) exhibited a short circuit current density (JSC) = 18.63 mA cm(-2), an open circuit voltage (VOC) = 0.65 V and a fill factor (FF) = 0.53, resulting in an overall power conversion efficiency (PCE) = 6.4%. While the DSC using as deposited CZTS film as a CE showed the PCE = 3.7% with JSC = 13.38 mA cm(-2), VOC = 0.57 V and FF = 0.48. Thus, the spray deposited CZTS films can play an important role as a CE in the large area DSC fabrication.

Spray process under an electric field was used for the deposition of zinc oxide (ZnO) electron transport layer by applying a DC voltage to the nozzle in order to make the layer smoother, highly crystalline and defect free having good electrical and optical properties. The nanostructure formed differed from that in the spray deposited ZnO layer without applying any voltage. The photovoltaic performance of the inverted organic solar cells (IOSC – ITO/ZnO/P3HT:PCBM/Ag) made using the nanostructured layer (deposited with the applied voltage=1000 V) and the cell stability were found to improve in comparison with the devices made using the nanostructured layer with the applied voltage=0 V. A change in the surface morphology of ZnO layer occurred with time and its effect on the cell performance was investigated. Photoluminescence (PL) spectra as well as XPS spectra showed that defects related mainly to oxygen vacancies were reduced in the spray deposited ZnO layer with the applied voltage=1000 V. This resulted in a higher IOSC efficiency (~2.7%) and good stability for a long duration (~105 days) with only 20% degradation in PCE. On the other hand, there was a 46% degradation in PCE of IOSC using spray deposited ZnO layer without applying voltage.

The fluorine doped tin oxide film has been deposited on 10 cm × 10 cm glass substrate by using spray technique with a voltage applied between the nozzle and an annular electrode placed 2 mm below the nozzle. The effect of the electric field thus created during the spray deposition on structural, optical and electrical properties of SnO2:F (FTO) film was studied. X-ray diffraction pattern revealed the presence of cassiterite structure with (2 0 0) orientation for all the FTO film. SEM study revealed the formation of smooth and uniform surface FTO film under the electric field over the entire substrate area. The electrical measurements show that the film prepared under the electric field (for an applied voltage of 2000 V) had a resistivity ∼1.2 × 10−3 Ω cm, carrier concentration ∼4.21 × 1020 cm−3 and mobility ∼14.48 cm2 V−1 s−1. The sprayed FTO film have the average transmission in the visible region of more than about 80%.

An electric field assisted spray deposition method is employed for improving the perovskite film morphology, crystallinity, and surface coverage, and for further fabricating an efficient solar cell. By applying different voltages ranging from 0.5 to 2.0 kV during spray deposition, we observed a large variation in the film morphology and surface coverage compared to those fabricated without an electric field, which is due to improved atomization from the Coulomb fission process. The optimized applied voltage of 1.5 kV during spraying led to completion of the reaction between CH3NH3I and PbI2 on a hot substrate for pure phase CH3NH3PbI3 thin film formation with improved grain growth and surface coverage. The cells fabricated using perovskite films showed clear applied voltage dependence in the energy conversion process and alleviation in J-V hysteresis; with 1.5 kV applied voltage the average cell efficiency of 8.9% was obtained compared to films fabricated without applying voltage providing only 6.5%. The best efficiencies are 10.9% and 7.37% for applied voltages of 1.5 kV and 0 kV, respectively. The enhancement in efficiency with applied voltage is due to the formation of more uniform and dense films with large perovskite crystals, which resulted in efficient electron transportation (enhanced photocurrent and modified series and shunt resistances) by minimizing the charge carrier recombination at grain boundaries (resulting in enhanced open circuit voltage). With further optimization of the perovskite film thickness by adjusting the CH3NH3I spray volume, the average cell efficiency of ∼11.0% was obtained.

Spray deposited kesterite (Cu2ZnSnS4) thin films were annealed in a controlled sulphur environment at 500˚C for one hour. Temperature dependence measurement of the electrical conductivity indicated two types of conduction are present: (i) at low temperatures due to nearest neighbor hooping (NNH) and (ii) at high temperatures due to hole excitation into the conduction. The as deposited films showed both the conduction mechanisms, but on annealing the CZTS film, the conduction takes place only due to hole excitation into the conduction band. The absence of NNH conduction is indicative of the effect of annealing in removing the defect levels which can be important for improving the device performance.

Spray deposition of ZnO film was carried out. The uneven growth of ZnO nanostructures is resulted for spray deposited ZnO film. Application of DC voltage (1000V) during spray deposition provides formation of pea like structures with uniform coverage over the substrate. Electric field assisted spray deposition provides increased crystallinity with reduced resistivity and improved mobility of the ZnO film as compared to spray deposited ZnO film without electric field. This with large area deposition makes the process more efficient than other techniques.

ZnO film was deposited using spray technique. The application of electric field (applying a DC voltage = 700V to the nozzle) during spray deposition provide compact nanostructured film of ZnO as compared to agglomerated ZnO film deposited using spray process. The ZnO film deposited after applying DC voltage during spray process showed good crystallinity as well as transmittance in the visible range. Use of this crystalline, compact layer of ZnO in inverted organic solar cell (ITO/ZnO/P3HT: PCBM/Ag) provide improved efficiency of 2.8% with JSC of 14.0 mA/cm2, VOC of 0.55V and FF of 36%. Thus the process remove the need of any post deposition treatment to improve the film quality as well as solar cell performance.

Zinc sulphide (ZnS) thin films were deposited on soda lime glass substrate using spray technique with a DC voltage (300 V) applied to the nozzle to create an electric field during the spray deposition. Spray deposition of ZnS film under an electric field, resulted in change of the surface morphology, transmission, and enhancement in crystallinity of the film. The band gap of the spray deposited ZnS film was found to be 3.62 eV. Transparent ZnS film with the benefit of large area and low cost spray technique can be suitable for solar cell window layer application.

Gold nanoparticles with varying sizes were prepared by the spray process under an electric field (DC voltages of 0 V and 1 kV applied to the nozzle) for studying their role in inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag). The application of electric field during the spray process resulted in a smaller size (35 nm as compared to 70 nm without the electric field) of the nanoparticles with more uniform distribution. This gave rise to a difference in the surface plasmon resonance (SPR) effect created by the gold nanoparticles (Au NPs), which then affected the solar cell performance. The photovoltaic performances of plasmonic inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag) using spray-deposited Au and ZnO layers (both at 1 kV) showed improved efficiency. Fast exciton quenching in the P3HT:PCBM layer was achieved by using a spray-deposited Au layer in between ITO and ZnO layers. The absorption spectra and internal power conversion efficiency (IPCE) curve showed that the Au nanoparticles provide significant plasmonic broadband light absorption enhancement which resulted in the enhancement of the JSC value. Maximum efficiency of 3.6% was achieved for the inverted organic solar cell (IOSC) with an exceptionally high short circuit current density of ∼15 mA cm(-2) which is due to the additional photon absorption and the corresponding increase observed in the IPCE spectrum. The spray technique can be easily applied for the direct formation of Au nanoparticles in the fabrication of IOSC with improved performance over a large area.

We report a simple method to mitigate ultra-violet (UV) degradation in TiO2 based perovskite solar cells (PSC) using a transparent luminescent down-shifting (DS) YVO4:Eu3+ nano-phosphor layer. The PSC coated with DS phosphor showed an improvement in stability under prolonged illumination retaining more than 50% of its initial efficiency, whereas PSC without the phosphor layer degraded to ∼35% of its initial value. The phosphor layer also provided ∼8.5% enhancement in photocurrent due to DS of incident UV photons into additional red photons. YVO4:Eu3+ layer thus served a bi-functional role in PSC by reducing photo-degradation as well as enhancing energy conversion efficiency.

Spray process under different applied voltages (0 V to 700 V) is used for the deposition of poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL). The deposition of PEDOT:PSS film by spray process under the effect of electric field results in smoother film morphology, increase in conductivity and reduction in the sheet resistance. The improvement in surface morphology and conductivity enhancement of PEDOT: PSS films are the key to the improvement in the J–V characteristics of ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell structures. The XPS peak height for PEDOT at 164.4 eV increased by 47% and that for PSS at 169.0 eV decreased by 30%, showing that the enhancement in the conductivity of the films deposited under electric field is due to the change in the PEDOT: PSS ratio. The organic solar cell using the electric field (created using 700 V) assisted spray deposited PEDOT:PSS film exhibit 42% and 69% improvement in the short circuit current density(Jsc) and power conversion efficiency, respectively, in comparison to the cells having PEDOT:PSS films deposited without the electric field.

The thin films of Cu 2 ZnSnS 4 (CZTS) have been successfully deposited on soda lime glass by spin coating technique. CZTS films were prepared by spin coating of a solution prepared by dissolving of copper (II) chloride, zinc (II) chloride, tin (IV) chloride and Thiourea in 2-Methoxyethanol. The X-ray diffraction studies showed the formation of kesterite phase with the peaks corresponding to (112), (220) and (312) planes. Raman spectrum indicated the presence of principal kesterite peak at 333 cm −1 . SEM study showed that the surface of CZTS film was uniform. The electrical measurements showed the p-type conductivity, resistivity ∼0.014 Ω-cm with carrier concentration ∼7.9x10 19 cm -3 and mobility ∼5.43 cm 2 V -1 s -1 at room temperature. CZTS film showed optical absorbance of 104 cm-1 with optical band gap of 1.5 eV. Thus, CZTS films can be made using a simple spin coating technique, but improvement in the film properties by post deposition needs to be done for making photovoltaic quality films.

Cobalt sulphide (CoS) films are potentiodynamically deposited on fluorine-doped tin oxide (FTO) coated glass substrates employing one, three and five sweep cycles (CoS-I, CoS-III and CoS-V respectively). Analysis of the CoS-III film by impedance spectroscopy reveals a lower charge transfer resistance (R-CT) than that measured for Pt CE (0.75 Omega cm(-2) and 0.85 Omega cm(-2), respectively). The CoS films are used as counter electrodes (CE) in dye-sensitized solar cells (DSSCs) featuring the combination of a high absorption coefficient organic dye (C218) and the cobalt-based redox electrolyte [Co(bpy)(3)](213+). DSSCs fabricated with the CoS-III CE yield the highest short-circuit current density (J(SC)) of 12.84 mA cm(-2), open circuit voltage (V-OC) of 805 mV and overall power conversion efficiency (PCE) of 6.72% under AM 1.5G illumination (100 mW cm(-2)). These values are comparable to the performance of an analogous cell fabricated with the Pt CE (PCE = 6.94%). Owing to relative lower cost (due to the inherit earth abundance of Co) and non-toxicity, CoS can be considered as a promising alternative to the more expensive Pt as a CE material for next-generation DSSCs that utilize organic dyes and cobalt-based redox electrolytes. (C) 2014 Elsevier B.V. All rights reserved.