Characterisation and optimisation of hybrid polymer/metal oxide photovoltaic devices

Imperial Users onl

Realization of the welding of individual TiO2 semiconductor nano-objects using a novel 1D Au80Sn20 nanosolder

Individual semiconductor nanowires (NWs) TiO2 were successfully welded together using novel one-dimensional (1D) Au80Sn20 (mass ratio) nanosolders at the nano-scale for the first time. The nanosolders were electrodeposited into nanoporous templates to form a 1D structure, and their morphology, crystal structure, chemistry and elemental electronic states were systematically characterized. Individual Au80Sn20 nanowires were proved to consist of mixed crystal phases, including a Au5Sn phase with a trigonal structure, a AuSn phase with a hexagonal structure and a small SnO2 phase produced the by oxidation of the surface portion. Chemical analysis indicated that the composition was Au80Sn20. The testing of the welding capability by either in situ TEM or in situ SEM by nanomanipulators and infiltration experiment revealed a good wet ability and diffusion ability between the Au80Sn20 nanosolder and the TiO2 nanowire. It is believed that our study contributes to the field a special nanosolder for future nano-scale welding techniques, which also make the bonding of titanium-based semiconductor oxide nanomaterials at the nano-scale a reality

Determinants of Efficiency of Commercial Banks in India After Global Crises

This study contributes to the bank efficiency literature by estimating the technical efficiency, pure efficiency, and scale efficiency of banks in four different ownership groups in India from 008-09 to 019-20, utilizing the DEA method and three alternative approaches to choosing inputs and outputs of banks-intermediation approach, value-added approach, and operating approach. It also uses the Tobit estimation procedure to identify the factors determining the variations in the technical efficiency of banks. Results indicate a high degree of inefficiency of several banks during the study period, and there is greater scope for improving their performances. Sizable scale inefficiency exists, and banks are likely to lose sizable output. The results also indicate that banks with a larger capital adequacy ratio, young banks, larger banks, or more profitable banks are more efficient. Foreign banks and nationalized banks are more efficient than private domestic banks. We hope that the findings of this study will be useful to international agencies and other stakeholders in evaluating and improving the performance of Indian banks

Development and Application of a Stream Flashiness Index based on Imperviousness and Climate using GIS

This work examines the relationship between imperviousness, climate, and the Richards-Baker (R-B) index, a measure of ow variability. Regression equations to predict the R-B index are developed for annual, cool, and warm seasons. The re- gression equations developed, are calibrated using stream ow data from 1970-2000 for 29 USGS streamgages throughout Maryland. Regression equations for the R-B ashiness index are developed as a function of imperviousness, precipitation char- acteristics, and drainage area. The relationship is used to estimate stream quality conditions throughout Maryland for present and future land use and climate. The regression equations are used to calculate the future stream ow variability by pro- jecting the R-B index predictors to re ect the following conditions: (1) Increasing imperviousness only, (2) Climate change only, and (3) Jointly changing impervious- ness and climate. Finally, the relationship between R-B index and stream quality is studied

A Structural and Biochemical Study on the Stapholococcal Surface Proteins Interactions with Host Extracellular Proteins

Staphylococcus aureus (S. aureus), a gram positive bacterium, expresses multiple surface proteins (MSCRAMMs) that target host proteins for its colonization on the host tissue and later for the pathogenesis. ClfA is a virulence factor that interacts with fibrinogen (Fg) and the interaction of ClfA with the Fg is crucial for the pathogenesis. The virulence potential of ClfA/Fg interactions in the pathogenesis of S.aureus had been proven in sepsis and endocarditis infection animal models. ClfB is a chief colonizing factor that interacts with multiple host proteins like loricrin, cytokeratin-10, dermokine and Fg. The binding mechanism and structure of the ClfB:Ln complex is crucial for designing inhbitors against ClfB that aid in preventing the host colonization of S. aureus. My thesis work includes two chapters (1) crystal structure of ClfA with a proteolytic fragment of Fg (FgD). (2) Crystal structure of ClfB in complex with Ln. Chapter-1 results describe the structure of ClfA/FgD complex and identify the residues involved in the interactions of ClfAcc and Fg. The results of this chapter explains the structural basis for the fg mediated virulence of ClfA and the mechanism of Fg interactions of ClfA of S. aureus and its functional homologs fbl of S. lugdunensis and SpsD of S .pseudintermedius. The ClfAcc interacting region in Fg overlaps with the M1 protein of S. pyogenes and Fg interacting site in ClfA overlaps with the ‘tefibazumab’ interacting site. Chapter-2 results describe the structure of the ClfB/Ln complex and the mechanism of ClfB/Ln interactions. Comparison of ClfB/Ln structure with other ClfB ligand peptide complexes (Ck10, DK and Fg) shows that ClfB/Ln binding mechanism is unique and different from the previously known Dock, Lock and Latch mechanism of ClfB ligand binding. My study was the first structure to show that, the Ln peptide can induce the dimerization of ClfB which is not observed in the interaction of ClfB with other known ligands. Furthermore, the crystal structure led to the discovery of an additional ligand binding site on top of the N3 subdomain in ClfB which is also present in other MSCRAMMS that forms the basis for chapter-1

A facile impregnation synthesis of Ni-doped TiO2 nanomaterials for dye-sensitized solar cells

This study reports a facile impregnation method for synthesizing Ni-doped TiO2 nanomaterials using P25-TiO2 as a starting material. The as prepared nanomaterials were subjected to structural and optical characterizations and subsequently employed in photovoltaic studies. X-ray diffraction (XRD) and Raman studies confirmed that Ni doping did not alter the anatase and rutile contents of P25-TiO2. Also, the presence of the constituent dopants and their ionic states were confirmed by Energy-Dispersive X-ray (EDX) and X-ray photoelectron (XPS) spectroscopies. Topographic Atomic Force Microscopic (AFM) images illustrated that Ni doping had increased the surface roughness of the TiO2. Optical characterization by UV-Visible spectroscopy revealed that the Ni doping had caused red shift in light absorption due to reduced TiO2 bandgap and improved the dye adsorption on TiO2 films. Then, the photocurrent–photovoltage property of the fabricated devices was investigated and the optimized 0.10 wt% Ni-doped TiO2 photoanode based device exhibited pronounced power conversion efficiency (PCE) of 6.29% under air mass (AM) 1.5 conditions (100 mWcm−2, 1 sun). Improved charge transport properties were also observed by the electrochemical impedance spectroscopic (EIS) study for the device with optimized Ni-doped TiO2 compared to the control device.publishedVersio

Lithium doped poly(3-hexylthiophene) for efficient hole transporter and sensitizer in metal free quaterthiophene dye treated hybrid solar cells

Abstract This work focuses on the role of Lithium doped Poly(3-hexylthiophene)(P3HT) in metal-free quaterthiophene (4T) dye treated Titanium dioxide (TiO2) based hybrid solar cells. The dye treated hybrid solar cells with Lithium doped P3HT showed efficiencies (3.95%) of nearly a factor of four times higher than the pristine P3HT based control TiO2/4T/P3HT devices (1.04%). The enhancement of the efficiency is mainly due to highly efficient charge collection attributed to enhanced charge transport and light harvesting properties of Lithium doped P3HT polymer. The optimized solar cells with Lithium doped P3HT showed a high short circuit current density over 13 mA/cm2, under simulated irradiation of intensity 100 mW/cm2 with AM 1.5 filter. This significant increase in current density in TiO2/4T/doped P3HT solar cell is also confirmed by both the broadened External Quantum Efficiency spectrum and significant photoluminescence quenching upon replacement of pristine P3HT with doped P3HT on 4T dye treated TiO2 electrode. With Lithium doped Spiro-OMeTAD instead of Lithium doped P3HT, similar devices showed efficiencies over 3.30% under simulated irradiation of 100 mW/cm2 with AM 1.5 filter

Enhancement of hole-mobility in Hybrid Titanium Dioxide / Poly(3-hexylthiophene) Nanocomposites by Employing an Oligothiophene dye as Interface Modifier

Hole-mobility in nanocrystalline TiO2/P3HT composites is increased by over an order of magnitude when the TiO2 surface is treated with a 3-hexylthiophene oligomer bearing a cyanoacrylic acid group (4T).</p

Enhanced Photovoltaic Properties of Dye-Sensitized Solar Cells through Ammonium Hydroxide-Modified (Nitrogen-Doped) Titania Photoanodes

Doping is a unique strategy to modulate the optical and electronic properties of semiconducting materials. This study reports a facile approach to fabricate nitrogen-doped TiO2 (N-doped TiO2) photoanode for DSSC application. A solid-state reaction was employed to synthesize a series of N-doped TiO2 nanoparticles with different volumetric ratios of nitrogen dopant and the TiO2 host. The NH4OH as a nitrogen dopant was combined with P25-TiO2 via grinding followed by calcination at 500°C. The synthesized nanoparticles were extensively characterized by XRD, XPS, EDX, SEM, and TEM techniques. XRD results suggested that the incorporation of nitrogen had not altered the structure of the TiO2 lattice, and the presence of nitrogen was confirmed through the XPS and EDX spectroscopies. SEM and TEM images, obtained before and after N doping, showed that N-doped TiO2 nanoparticles with low amounts of NH4OH (10 and 20 μL) had retained their spherical shapes and sizes while use of higher amounts of the N dopant (30 and 40 μL) had led to agglomeration of nanoparticles. BET and BJH analyses revealed that the optimized N-doped TiO2 with 20 μL of NH4OH (20N-TiO2) possesses the highest average pore diameter of 15.99 nm. Furthermore, the UV-visible spectroscopic analysis confirmed a red shift in the optical absorption edge on N doping and the corresponding bandgap reduced from 3.15 to 2.94 eV with increase in the amount of NH4OH from 0 to 40 μL. Eventually, DSSCs were fabricated using the prepared pure TiO2 and N-doped TiO2 photoanodes, N719 dye, I−/I−3 electrolyte, and Pt counter electrode, followed by investigating their performance under simulated irradiation with 100 mW/cm2 intensity with AM 1.5 filter. The photoanode doped with 20 μL of NH4OH (20N-TiO2) exhibited the highest power conversion efficiency (PCE) of about 6.16%, which was 20% higher than that of the control device, with improved JSC. This enhancement in JSC could be predominantly attributed to higher dye uptake along with marginal contribution by reduced rate of recombination. Among the reported studies on DSSCs with N-doped P25-TiO2 photoanodes, our method gives the best efficiencies for the DSSCs.publishedVersio