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Investigation of temperature-dependent photoluminescent properties of potassium perylene-3,4,9,10-tetracarboxylate (K4PTC), a molecule with no internal rotational degrees of freedom, shows aggregation-induced enhanced emission at room temperature. The different excitonic emission processes are dependent of temperature, some of which quenches in an intermediate temperature range (from 50 to 150 K). The exciton excited states switching phenomenon from "dark" to "bright" states is observed and its explained using Herzberg-Teller selection rule. K4PTC is a molecule comparable to the size of its precursor, perylene-3,4,9,10-tetracarboxylic anhydride (PTCDA) and is highly soluble in water, contrary to PTCDA, which is poorly soluble in most solvents. Powder x-ray diffraction measurements corroborate a lesser degree of ordering of bulk K4PTC compared to bulk PTCDA. The green luminescent molecule could, in principle, be used as a biomarker, or in photodynamic therapy, if further studies show relatively low toxicity.

International audience; Mixed-halide based hybrid perovskite semiconductors have attracted tremendous attention as a promising candidate for high efficient photovoltaic and light-emitting devices. However, these advanced perovskite materials may undergo phase segregation under light illumination due to halide ion migration, affecting their optoelectronic properties. Here, we report photo-excitation induced phase segregation in triple-cation mixed-halide perovskite films that yields to red-shift in photoluminescence response. We demonstrate that photo-excitation induced halide ion migration leads to the formation of smaller-bandgap iodide-rich and larger-bandgap bromide-rich domains in the perovskite film, where the phase segregation rate is found to follow the excitation power-density as a power law. Results confirm that charge carrier lifetime increases with redshift in photoluminescence due to the trapping of photo-excited carriers in the segregated smaller-bandgap iodide-rich domains. Interestingly, we found that these photo-induced changes are fully reversible and thermally activated when the excitation power is turned off. A significant difference in activation energies for halide ion migration is observed during phase segregation and recovery process under darkness. Additionally, we have investigated the emission linewidth broadening as a function of temperature which is governed by the exciton-optical phonon coupling. The mechanism of photo-induced phase segregation is interpreted based on excitonphonon coupling strength in both mixed and demixed (segregated) states of perovskite film.

In situ current–voltage characteristics of Nb-doped TiO2/p-Si-based heterojunction diode have been studied under dense electronic excitations of 84-MeV Si6+ ions. The diode parameters such as ideality factor ( $\eta $ ), barrier height ( $\phi _{B}$ ), reverse saturation current ( ${J}_{s}$ ), and series resistance ( ${R}_{s}$ ) are found to be a strong function of ion irradiation fluence. The observed anomalies of fluence dependence of barrier height and ideality factor are explained in terms of irradiation-induced created defects complexes, modification of interface states and structural properties of Nb-doped TiO2 (NTO) layer. Several mechanisms such as barrier height inhomogeneity, donor defects-induced enchantment in n-NTO layer conductivity, and various current conduction mechanisms involved at different voltage ranges are discussed as a function of fluence with the help of constructed energy band diagram. Such in situ studies on n-NTO/p-Si heterojunction diode under radiation harsh environment are very appropriate for the better understanding of heterojunction interface properties and make it suitable for use in aerospace industry and nuclear reactors.

The semiconductor-to-metal transition (SMT) is reported in nanocomposite films of wide bandgap semiconducting oxides. This study offers insight into the existing models of temperature-dependent charge transport by tailoring the defects induced disorder into the lattice by swift heavy ions irradiation. The structural studies show the presence of both cadmium oxide and zinc oxides phases and confirm the nanocomposite nature of films. Temperature-dependent charge transport properties of the nanocomposite films were studied by carrying out four-probe resistivity measurements in the wide temperature range of 35–300 K. Here, the swift heavy ions irradiated films demonstrated the tuning of SMT phenomena and its transition temperature upon increasing fluence of irradiation. These irradiation effects are discussed in terms of irradiation-induced defects/disorders into the lattice. The change in the nature of temperature-dependent resistivity in pristine and irradiated films has been envisaged with a quantitative fit of experimental data by invoking quantum correction to conductivity (QCC). Our results are consistent with QCC model, which essentially depends on weak localization and renormalized electron-electron interactions. Thus, this work extends the validity of the weak localization model to composite systems.

The re-crystallization kinetics and rutile to anatase reversible phase transformation (PT) in nano-crystalline titanium dioxide (TiO2) are reported. Initially, an amorphous TiO2 film is used for the present study and in situ isothermal annealing dependent nucleation and growth kinetics of anatase and rutile phase is studied at low temperature (∼523 K) and well explained using Johnson–Mehl–Avrami-Kolmogorov (JMAK) model. The anatase nanocrystallite (NCs) transformation into rutile phase is reported with isothermal annealing for longer time and temperature dependent annealing in lower temperature range 523 K–673 K and explained using interface-nucleation mechanism. Furthermore, the thermodynamic stability of rutile NCs and lattice stress-induced reversible PT in nano-sized rutile TiO2 are confirmed in moderate temperature range (623 K - 973 K) and well explained using x-ray diffraction, micro-Raman spectroscopy and near edge x-ray absorption fine structure spectroscopy studies. However, annealing at higher temperature (1123 K - 1323 K) induces the growth of anatase NCs and their natural transform into rutile phase are explained by well-known dissolution–precipitation mechanism. Activation energy of rutile PT is quantified and found higher for dissolution-precipitation mechanism than that for interface nucleation at earlier stage. Thus, overall PT kinetics at different temperature range is well understood by invoking in three step mechanism: I) early stage anatase-to-rutile transformation is dominated by interface-nucleation, II) then intermediate stage reversible rutile-to-anatase PT and, III) at later stages, anatase-to-rutile PT is controlled by dissolution–precipitation mechanism.

An intriguing phenomenon of the negative differential resistance (NDR) in conducting polymer-metal oxide hybrids is manifested upon measuring the In-situ current-voltage characteristics. Anomalous evolution of low current state leading to the electrical bistability has also been observed as an induced effect at low ion irradiation doses and explained by invoking ordering of the polymer chains and electric-field induced charge transfer mechanisms. Later, a disorder leading to damage is observed at higher doses by the diffusion of irradiation-induced electrically active free radicals and defect centers within the active region of the device. This leads to the device into a high current state of electrical bistability. Further, the observed NDR is attributed to the tunneling of carriers along with transient charging of molecular chains by trapping of charge carriers at the heterojunction interfaces induced by ion irradiation. It is further confirmed by anomalous response of voltage shifting in the conductance response upon incremented doses of irradiation. Efforts are envisaged to understand the processes of irradiation interactions and their influences on the transport of charge carriers by fitting experimental data using various conduction models such as Ohmic conduction, space-charge-limited conduction (SCLC), and trap-assisted SCLC. Thus, such low-cost and simple design devices have lots of potential applications for radiation harsh environments and could be easily integrated into the existing silicon-based technology.

Cu-doped Zinc Oxide (Cu ZnO) thin films have been prepared on silicon and quartz substrates by sol-gel spin coating method. These films were further annealed at 700 °C in controlled oxygen environment for improving crystalline quality and stoichiometry. In order to understand the material properties of thin films, X-ray Diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, Raman Spectroscopy and UV–Visible Spectroscopy methods have been used in the present study. Polycrystalline nature of the Cu ZnO thin films is confirmed by structural analysis with increased crystallite size upon increasing the doping concentrations of the thin films. The phonon evolution at different doping concentrations is understood by Raman spectroscopy, thus confirming the wurtzite phase stability of the thin films with increase in crystallite size and presence of mixed phases have also been reported. In addition, widening and narrowing of band gap for the Cu ZnO thin films have been discussed in optical studies. This anomalous behavior in band gap tuning such as widening (+0.5 eV) and narrowing (−0.6 eV) under different doping concentrations and annealing temperature is understood by the influence of induced stress effects due to creation of intrinsic defects with band gap renormalization and secondary phase formation.

Study reports the effect of swift heavy ion (SHI) irradiation induced phase transformation in undoped and Niobium doped anatase TiO2 composite thin films. Investigations were carried out at different densities of electronic excitations (EEs) using 120 MeV Ag and 130 MeV Ni ions irradiations. Films were initially annealed at 900 °C and results revealed that undoped films were highly stable in anatase phase, while the Nb doped films showed the composite nature with the weak presence of Niobium penta-oxide (Nb2O5) phase. The effect at low density of EEs in undoped film show partial anatase to rutile phase transformation; however doped film shows only further growth of Nb2O5 phase beside the anatase to rutile phase transformation. At higher density of EEs induced by Ag ions, registered continuous ion track of ∼3 nm in lattice which leads to nano-crystallization followed by decomposition/amorphization of rutile TiO2 and Nb2O5 phases in undoped and doped films, respectively. However, Ni ions are only induced discontinuous sequence of ion tracks with creation of damage and disorder and do not show amorphization in the lattice. The in-elastic thermal spike calculations were carried out for anatase TiO2 phase to understand the effect of EEs on anatase to rutile phase transformation followed by amorphization in NTO films in terms of continuous and discontinuous track formation by SHI irradiation.

Fe 3 C nanorod filled inside carbon nanotube has been irradiated inside transmission electron microscope at both room and high temperature. In-situ response of Fe 3 C nanorod as well as CNT walls has been studied. It has been found that when electron irradiation is performed at room temperature (RT), nanorod first bends and then tip makes at the end whereas at high temperature (∼490 °C) nanorod slides along the tube axis and then transforms into a faceting particle. Extrusion of solid particle filled in the core of CNT has also been demonstrated. It is suggested that these morphological changes in nanorod may have happened due to the compression which was generated either by shrinkage of tube or by local electron beam heating. Presented results demonstrate that CNT core could be used as nano-container or reactor.

In present work, ion irradiation induced nanostructuring has been exploited as an efficient and effective tool for synthesis of coupled plasmonics nanostructures by using 1.2 MeV Xe ions on Au/ZnO/Au system deposited on glass substrate. The results are correlated on the basis of their optical absorption, surface morphologies and enhanced sensitivity of evolved phonon modes by using UV Visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy (RS), respectively. Optical absorbance spectra of plasmonic nanostructures (NSs) show a decrease in band gap, which may be ascribed to the formation of defects with ion irradiation. The surface morphology reveals the formation of percolated NSs upon ion irradiation and Rutherford backscattering spectrometry (RBS) study clearly shows the formation of multilayer system. Furthermore, RS measurements on samples are studied to understand the enhanced sensitivity of ion irradiation induced phonon mode at 573 cm−1 along with other modes. As compared to pristine sample, a stronger and pronounced evolution of these phonon modes is observed with further ion irradiation, which indicates localized surface plasmon results with enhanced intensity of phonon modes of Zinc oxide (ZnO) material. Thus, such plasmonic NSs can be used as surface enhanced Raman scattering (SERS) substrates.

A huge band gap tuning and low temperature transport phenomenon in highly transparent antimony doped tin oxide thin film (Sb:SnO 2 ) under the influence of swift heavy ions irradiation (SHII) is reported. Structural analysis shows an enhancement in crystallinity at initial fluence of irradiation followed by amorphization at higher fluences. Films were also well studied for their surface morphology by atomic force microscopy and scanning electron microscopy. Band gap analysis reveals a drastic band gap narrowing around 1.1 eV upon SHI irradiation. Transport measurements show that the high conductivity and the carrier concentration decrease upon increase in the fluence of irradiation. The mechanism of charge carrier transport investigated at low temperature is attributed to nearest neighbor hopping (NNH) and variable range hopping (VRH) in different temperature regimes. Origin of the band gap tuning is understood in framework of Burstein–Moss (BM) shift, Quantum Confinement (QC) effect and band-tailing states in amorphous semiconductors.

Decomposition of indium oxide nanoparticles (IONPs) sandwiched between zinc oxide (ZnO) thin films by energetic ions is reported. Multi-layers thin films were deposited using RF magnetron sputtering at room temperature, consisting two thin indium oxide layers sandwiched between three ZnO layers. Films exhibit very high transparency in the visible region. A sharp near band edge absorption with exciton absorption peak in the film annealed at the highest temperature was also observed. The structural and optical properties reveal that the as-deposited films show the formation of IONPs around the interface, which further grow upon increasing in annealing temperature. However, irradiation induces the decomposition of IONPs for the possible formation of single phase indium doped ZnO (IZO). The mechanism of the decomposition of IONPs is understood by the creation of ion tracks in IO. The track radius ( R e ) of 5.9 nm is calculated in the framework of thermal spike model. Therefore, the IONPs with diameter≤2 R e decomposed or amorphized between the crystalline ZnO layers; while the IONPs with diameter>2 R e show reduction in size by the electronic sputtering from the IONPs surface under the thermo-elastic effects.

Raman scattering were used to study lattice damage in nanocrystalline zinc oxide (nc-ZnO) thin films implanted with 300 KeV Ar and 1.2 MeV Xe ions at different ion fluences and ion fluxes. Raman spectra of all of the implanted samples show a broad Raman band at the lower Raman shift side along with A1 (LO) phonon mode. The A1 (LO) phonon modes get evolved with an increase in ion fluence with the reduction in the intensity of E2 (high) mode which is the characteristic mode of the wurtzite phase of ZnO. The implanted films show broadening and softening of A1 (LO) phonon mode upon an increase in ion fluences and observed to be more prominent in the case of 1.2 MeV Xe ions as compared to 300 KeV Ar ions. The evolution of A1 (LO) phonon mode and broadening of Raman band assigned to the damage induced in the system upon ion-implantation and correlated well with the damage profile, while the peak broadening and softening could be assigned to the stress-induced into the films due to implantation. Thus, for a better understanding, the Raman tensor of first-order optical Raman modes in back-scattering geometry is also presented in the manuscript.

The deposition of Cd x Zn 1−x O thin films with different cadmium concentrations i.e., x = 0.0, 0.05, 0.20 by sol–gel spin coating is reported. The doping fraction of Cd in ZnO films was measured by Rutherford backscattering spectrometry (RBS), while the surface morphology was studied by scanning electron microscopy (SEM). Grazing incidence X-ray diffraction (GIXRD) study was carried out for the structural investigations and reveals hexagonal wurtzite structure with polycrystalline nature. The various structural parameters are calculated including the lattice constants ‘ a’ and ‘ c ’, stress ( σ ), strain ( e ) and internal parameter ( u ). For x = 0.20 Cd content, the formation of secondary phase of the cubic CdO at 33.12° (111) and 38.41° (200) is observed and this is further confirmed by micro-Raman studies, where the TO mode emerges at ∼261.5 cm − 1 . The basic wurtzite structure is maintained as ‘ c/a ’ ratio and internal parameter ‘ u ’ found to be closer to the ideal values. All the films are found to be highly transparent in the visible region and a bending of the near band edge (NBE) absorption is observed with Cd doping. It is further confirmed by calculating the Urbach energy ( E u ), which is found to be increased from 0.14 eV (for x = 0.0) to 0.26 eV (for x = 0.20) with maximum value for the lightly doped films i . e . x = 0.05. However, the optical band gap is found to decrease from 3.26 eV (for x = 0.0) to 3.08 eV (for x = 0.20).

In situ micro-Raman studies are reported to monitor the evolution of the tetragonal phase in a monoclinic zirconium oxide thin film under swift heavy ion irradiation with increasing ion fluences. Structural changes in the irradiated film are observed as compared to the virgin sample, evident from an evolution of the tetragonal phase beyond critical ion fluence. The interpretation of experimental data allows for an in-depth understanding of irradiation induced stiffening of phonon and crystalline-to-crystalline phase transformation in ZrO2 thin films. Irradiation induced peak broadening and uniform shifting of fundamental Raman modes are observed mainly in the anion (i.e., oxygen atom) dominant frequency region and give a direct indication of the accumulation of structural disorder in the oxygen sublattice of the ZrO2 film. A qualitative approach is followed to understand the kinetics of such a crystalline-to-crystalline phase transformation. Experimental results reveal that the cascade overlap model with the requirement of about six multiple ion impacts provides an excellent fit to data, and the same is further confirmed by x-ray diffraction data. Thus, this study suggests that such in situ studies envisage a better and more authentic insight into the kinetics of phase transformations under similar nonequilibrium conditions.In situ micro-Raman studies are reported to monitor the evolution of the tetragonal phase in a monoclinic zirconium oxide thin film under swift heavy ion irradiation with increasing ion fluences. Structural changes in the irradiated film are observed as compared to the virgin sample, evident from an evolution of the tetragonal phase beyond critical ion fluence. The interpretation of experimental data allows for an in-depth understanding of irradiation induced stiffening of phonon and crystalline-to-crystalline phase transformation in ZrO2 thin films. Irradiation induced peak broadening and uniform shifting of fundamental Raman modes are observed mainly in the anion (i.e., oxygen atom) dominant frequency region and give a direct indication of the accumulation of structural disorder in the oxygen sublattice of the ZrO2 film. A qualitative approach is followed to understand the kinetics of such a crystalline-to-crystalline phase transformation. Experimental results reveal that the cascade overlap model with ...

The formation of charge neutrality level (CNL) in highly conducting Cadmium oxide (CdO) thin films is demonstarted by the observed variation in the band gap upon annealing and doping. It may be explained by the observation that Tin (Sn) doping breaks the perfect periodicity of CdO cubic crystal structure and creates virtual gap states (ViGS). The level of local CNL resides at the branch point of ViGS, making the energy at which native defect’s character changes from predominantly donor-like below CNL to predominantly acceptor-like above the CNL and a schematic band diagram is developed to substantiate the same. Further investigations using soft x-ray absorption spectroscopy (SXAS) at Oxygen and Cadmium edges show the reduction of Sn4+ to Sn2+. The analysis of the spectral features has revealed an evidence of p-d interaction between O 2p and Cd 4d orbitals that pushes the valence band minima at higher energies which is symmetry forbidden at г point and causing a positive valance band dispersion away from the zone centre in the г ~ L, K direction. Thus, origin of the CNL is attributed to the high density of the Oxygen vacancies as confirmed by the change in the local electronic structure and p-d hybridization of orbitals.

A multifunctional hybrid heterojunction diode is developed on porous silicon and its current density-voltage characteristics reveal a good rectification ratio along with other superior parameters such as ideality factor, barrier height and series resistance. The diode also functions as an efficient photodiode to manifest high photosensitivity with high responsivity under illumination with broadband solar light, UV light, and green light. The diode is also carefully scrutinized for its sensitivity and repeatability over many cycles under UV and green light and is found to have a quick response and extremely fast recovery times. The notable responsivity is attributed to the generation of high density of excitons in the depletion region by the absorption of incident photons and their separation by an internal electric field besides an additional photocurrent due to the charging of polymer chains. The mechanisms of generation, injection and transport of charge carriers are explained by developing a schematic ...

The electronic structure and tuning of work function (WF) by electronic excitations (EEs) induced by swift heavy ions (SHIs) in anatase niobium-doped titanium dioxide (NTO) thin films is reported. The densities of EEs were varied using 80 MeV O, 130 MeV Ni and 120 MeV Ag ions for irradiation. The EE-induced modifications in electronic structure were studied by O K-edge and Ti L3,2 edge absorption spectra using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The reduction of hybridized O 2p and Ti 3d unoccupied states in the conduction band with a decrease in energy of the crystal field strength of ∼ 480 meV and the correlated effect on the decrease in the WF value of ∼ 520 meV upon increasing the total energy deposition in the lattice are evident from the study of NEXAFS and scanning Kelvin probe microscopy (SKPM), respectively. The observed stiffening in the low frequency Raman mode (LFRM) of ∼ 9 cm(-1) further validates the electronic structure modification under the influence of EE-induced strain in TiO6 octahedra. The reduction of hybridized valence states, stiffening behavior of LFRM and decrease in WF by nano-crystallization followed by amorphization and defects in NTO lattice are explained in terms of continuous, discontinuous amorphous ion tracks containing intestinally created defects and non-stoichiometry in the lattice. These studies are very appropriate for better insights of electronic structure modification during phase transformation and controlled Fermi level shifting, which plays a crucial role in controlling the charge carrier injection efficiency in opto-electronic applications and also provides a deeper understanding of the involved physical processes.

The perceptible progression of Raman modes of zinc oxide (ZnO) is studied in nanostructures film gap (Au (10 nm)/ZnO (70 nm)/Pt (50 nm)) system with 1.2 MeV Xe ion irradiation. Unattainable silent Raman modes of ZnO turn out to be strongly visible after ion irradiation. The creation of ion-beam–induced lattice disorder, defects, and impurities in a ZnO layer leads to breakdown the translational crystal symmetry that results in the origin of silent modes. The formation of hot-spots in the ZnO layer of the NFG system also supports the enhancement of the intensity of Raman modes. Overall results are attributed to combined effects of lattice disorder, defects, and impurities along with plasmonic effect and explained in the framework of elastic-thermal-spike formation.

The study of polymorphic ZrO2 and its structural stability of high temperature phases, such as tetragonal (t-ZrO2) and cubic (c-ZrO2) phases has been a pivotal issue for technological applications. In this work, nanocrystalline ZrO2 thin film was fabricated using the sol-gel route and comparative investigations were carried out for structural phases, surface morphology and optical band-gap for pure and yttrium doping. The changes in structural and optical studies were studied before and after irradiation with Ag9+, 120 MeV ion beam. The structural findings have shown complete transformation of phase with doping and irradiation. Two direct bands electronic structures have also evolved for doped samples under irradiation. These multiple band transitions in optical measurement could be attributed to the presence of oxygen point defects state in forbidden band gap. Presence of point defects is believed to be responsible for phase transformation/stabilization in pure zirconium oxide under irradiation.

Present manuscript reports on the creation of virtual gap states (ViGS) in sol–gel spin coated cadmium oxide thin films by tin doping and irradiation at different density of electronic excitations (EEs) induced by energetic ions. Effects of ViGS on charge neutrality level (CNL), which affects the modifications in band gap (BG) of such oxide semiconductors are investigated. Studies reveal that there were insignificant changes in the structural and morphological properties of the films. Interestingly, the transmittance spectrum shows insignificant changes in the films irradiated by low density EEs but an overall decrease in transmittance for high density EEs. However, Raman spectroscopy reveals a significant change in longitudinal optical (LO) modes with tin doping which get intensified and they exhibit an insignificant influence upon irradiation. The BG with respect to bulk is observed to be increased by 0.57 eV and 0.83 eV upon tin doping and irradiation, respectively. These variations are attributed to the combined effect of Burstein–Moss shift (BMS) and ViGS, which were created by tin doping and EEs. It is observed that density of ViGS strongly depends on the density of EEs. A schematic band diagram is also developed for demonstrating the observed influence of ViGS on band gap modifications. Thus the reported investigations are very interesting for the in-depth understanding of fundamental interactions and besides their possible potential applications in the development of optoelectronic devices.

The effect of volume fraction of silver (Ag) on the growth of silver nanoparticles (AgNPs) embedded in ion-irradiated silica films is reported. Films with low volume fraction (LVF) and high volume fraction (HVF) of Ag in silica matrix were prepared by magnetron co-sputtering. The growth of AgNPs under 120 MeV Ag ion irradiation is monitored in situ using grazing incidence X-ray diffraction (GIXRD). It is observed that the film with LVF shows the growth of AgNPs in a nearly single ion impact region, while the film with HVF shows a monotonous growth even in the region of multiple ion impacts. Rutherford backscattering spectrometry (RBS) experiments are also performed to determine the exact volume fraction of Ag in the silica matrix and to understand the role of sputtering and diffusion processes on the growth of AgNPs. Surface plasmon resonance (SPR) is carried out to obtain further evidence of the mechanisms of growth. Our study reveals that the growth of embedded nanoparticles strongly depends on the volume fraction of metal in the matrices and affects the dipolar interactions among such noble metal NPs. (C) 2013 Elsevier B.V. All rights reserved.

Nano-crystalline Nb doped anatase TiO2 (NTO) thin film was deposited on p-type Si substrate for fabrication of n-NTO/p-Si heterojunction photodiode using RF magnetron sputtering technique. Rutherford backscattering spectrometry and Raman spectroscopy results suggest the substitutional incorporation of Nb5+ ions in anatase TiO2 lattice, which is evidenced from large stiffening of Eg(1) and softening of B1g Raman modes. The current density-voltage (J-V) characteristics are measured and important diode parameters of n-NTO/p-Si heterojunction diode are determined, such as ideality factor, barrier height, and series resistance. Diode exhibits excellent behavior under dark condition as rectification ratio is found to be ∼7 × 102 with high forward current density ∼1.54 A/cm2 at 5 V. The n-NTO/p-Si heterojunction works as an efficient photodiode in reverse bias under simulated solar light illumination with high contrast ratio ∼225 at −2 V and very high photo responsivity ∼2.7 A/W at −5 V. The high photo responsiv...

Softening and stiffening of phonons in rutile titanium dioxide films are investigated by in situ micro-Raman studies during energetic ion irradiation. The in situ study minimized other possible mechanisms of phonon dynamics. Initial softening and broadening of Raman shift are attributed to the phonon confinement by structural defects and loss of stoichiometry. The stiffening of A1g mode is ascribed to large distortion of TiO6 octahedra under the influence of lattice strain in the (110) plane, which gives rise to lengthening of equatorial Ti-O bond and shortening of apical Ti-O bond. The shortening of apical Ti-O bond induces stiffening of A1g mode in the framework of the bond-order-length-strength correlation mechanism.

This paper reports on the development of high efficiency hybrid solid state blended dye sensitized solar cell (HssBDSSC) using ultrasonification process. Cell synthesized using conducting organic polymer as organic hole-transporting material together with BDs, while Poly (3-Octylthiopehene) (P3OT) and zinc oxide nanostructures (ns-ZnO) as electron-transporting material. BD is made in a composition, so that it can absorbed light in the entire visible region and provided the high electron injection. The HssBDSSC device structure such as indium tin oxide (ITO)/PEDOT:PSS/ns-ZnO+P3OT/BDs/Electrode is developed and an ultrathin layer of PEDOT:PSS is deposited on ITO for making Schottky contact. Device shows a very high conversion efficiency of 4.67%, Fill Factor (FF) 52.9%, open-circuit photo voltages 0.58 V and short-circuit photocurrents 15.1 mA/cm2 under 100 mW/cm2 visible band illumination. We propose an energy level alignment diagram to understand the photophysics of hybrid nanocomposites, which include charge carriers generation, separation, and transfer processes.