Thickness Of TiO2 Layer Research Articles

Low temperature processing of flexible planar perovskite solar cells with efficiency over 10%

A device fabrication method is reported to efficiently produce CH3NH3PbI3-based planar perovskite solar cells on polymer substrates with the entire process conducted at 150 °C or below. The hole blocking layer employed is a solution processed 100 nm thick mesoporous TiO2 layer. A gas-assisted perovskite deposition method is used to produce excellent coverage of the hole blocking layer by a ∼350 nm thick CH3NH3PbI3 film, resulting in high device performance reproducibility. We show that an average efficiency of 10.6 ± 1.2%, and a maximum efficiency of 12.3% are obtained for flexible perovskite solar cells, offering great promise for further improvement of this low-temperature, low-cost processing solar technology.

Effect of TiOx/TiO2 layer thickness on the properties of the pulsed laser deposited memristive device

AbstractMemristive properties of the pulsed laser deposited Pt/TiOx/TiO2/Pt heterostructures with different layer thicknesses are studied. It was found that the memristor device provides nonmonotonic dependence of the ratio of its resistance in low and high conductive states Roff/Ron on layers thickness. The maximum value of the ratio Roff/Ron = 200 is obtained when the thickness of both TiOx and TiO2 layers is 30 nm. The dependence of the stoichiometry index of deposited layers from their thicknesses is studied by means of Auger spectroscopy measurements. The nonmonotonic behaviour of the ratio Roff/Ron on layer thickness is discussed in terms of wide stoichiometry distribution through the amorphous TiOx/TiO2 structure. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Whey separation using TiO2-modified ultrafiltration membrane

Nowadays, the membrane filtration technique is a commonly used method for the separation of whey. The most significant limitation of membrane applications is fouling, which causes flux decline. During this work, regenerated cellulose membranes covered by TiO2-nanoparticles were investigated and applied to the separation of whey solution. Experiments were carried out in a dead-end ultrafiltration cell, and the changes in filtration parameters and the photocatalytic effects of the UV irradiated TiO2 modified membrane surface on the membrane fouling were examined. Our results showed that the water flux decreased with increasing TiO2 layer thickness, but the retention of turbidity and of COD increased. After separation, the membrane surface was cleaned by UV irradiation by means of photocatalytic oxidation. It was found that the original flux was recoverable, while the retention of the membrane decreased after cleaning.

The optimisation of dye sensitised solar cell working electrodes for graphene and SWCNTs containing quasi-solid state electrolytes

In this study, we report improved power conversion efficiencies of various carbon based quasi-solid state electrolytes/DSSCs by optimising the thickness of TiO2 layer, incorporation of TiO2 scattering layer and application of dense compact surface layers of TiO2 on working electrodes. Single wall carbon nanotube (SWCNT) based quasi-solid state electrolytes showed increased power conversion efficiencies from 1.43% to 3.49%. For the mixture of graphene and SWCNTs the power conversion efficiencies improved from 2.50% to 2.93%. However, graphene based quasi-solid state electrolytes displayed small decreases in power conversion efficiencies from 2.10% to 1.96% due to the more viscous nature of this electrolyte. Electrochemical Impedance Spectroscopy (EIS) demonstrated that the addition of these various carbon based nanomaterials into PMII significantly decreases the charge transfer resistance at the counter electrode and hence the much better performance obtained with carbon based quasi-solid state electrolytes compared to pure PMII based DSSCs.

Charge transfer and recombination kinetics in dye-sensitized solar cell using static and dynamic electrical characterization techniques

This study investigates the steady-state current–voltage characteristics, electronic and ionic processes and dynamic response of a TiO2 nanoparticle based dye-sensitized solar cell (DSSC) using impedance spectroscopy and current–voltage measurements. A dye-sensitized solar cell is fabricated with 12.26μm thick TiO2 layer, having power conversion efficiency of 2.9% under AM1.5 spectrum with photo-generated current density (JSC) of 7.2mAcm−2 and open-circuit voltage (VOC) of 672mV. The observed electrochemical phenomenon at the TiO2–electrolyte interface, in diffusion of electrolyte and in charge transfer at the counter electrode is mathematically modeled using alternating current (AC) electrical equivalent circuit. The effect of temperature and illumination on the steady state and dynamic parameters of dye-sensitized solar cells is also studied. The dynamic resistance of DSSC decreases from 440.7Ω to 78.6Ω with increase in illumination level from 20mWcm−2 to 100mWcm−2.

P‐88: All‐Inorganic Quantum‐Dot Light‐Emitting Devices Prepared by Solution‐Process Route

AbstractWe have fabricated all‐inorganic quantum‐dot light‐emitting devices(QDLED) with NiO as a hole transporting layer and TiO2 as a inorganic electron transporting layer. P‐type NiO and n‐type TiO2 charge‐transport layers were synthesized by sol‐gel method using spin‐coating technique. The thickness of TiO2 layer was optimized with different spin‐coating speed, and studied the luminescence characteristics of devices. Results indicated devices with 4000 rpm TiO2 layer has lower turn voltage 4.2V and higher EL intensity.

Performance of plasmonic silicon solar cells using indium nanoparticles deposited on a patterned TiO2 matrix

A considerable enhancement in the photovoltaic performance of plasmonic silicon solar cells using indium nanoparticles on a patterned TiO2 matrix was demonstrated experimentally. For characterizing the optical properties of the patterned TiO2 matrix with and without indium nanoparticles, the indium nanoparticles were deposited on the reference samples with 30- and 59.5-nm thick TiO2 layers and on the test samples with a patterned TiO2 matrix of 30- and 59.5-nm thick profiles. The optical reflectance of all samples before and after depositing indium nanoparticles on the TiO2 layer was measured. To study plasmonics and anti-reflective effects on solar cells, the cells with indium nanoparticles on a patterned TiO2 matrix with a profile coverage levels of 20%, 40%, 60%, and 80% were characterized. The photovoltaic performance under one-sun AM 1.5G illumination and the external quantum efficiency (EQE) of the cells were measured and compared. Compared to a bare cell, the plasmonic cell with a patterned TiO2 matrix of 40% profile coverage had a short-circuit current density (Jsc) enhancement of 30.98% (from 23.53mA/cm2 to 30.82mA/cm2) and a conversion efficiency (η) enhancement of 34.06% (from 9.63% to 12.91%). The improvements may be attributed to the combination of the reduction of reflection and the plasmonic scattering of incident-light by indium-nanoparticles on the patterned TiO2 matrix.

Nano-quantum size effect in sol–gel derived mesoporous titania layers deposited on soda-lime glass substrate

The TiO2 nanolayers were fabricated on soda-lime glass substrates with the application of sol–gel method and dip-coating technique. In the fabricated TiO2 layers, the quantum size effect can be observed. For the sake of comparison, we investigated also the TiO2 nanolayers fabricated on soda-lime glass substrates with a buffer silica layer. The fabricated layers were investigated with the application of optical measurement techniques and atomic force microscopy. The widths of energy gap and Urbach energy were determined. The diffusion of sodium ions Na+ from the glass substrate to the TiO2 layer brings about the non-monotonic dependence of the energy band gap on the thickness of TiO2 layer. In the TiO2 layers fabricated on soda-lime glass substrates pre-coated with a SiO2 layer, the influence of silicon ions on the direct energy band gap was found.

Preparation and characterization of magnetic-core titanium dioxide: Implications for photocatalytic removal of ibuprofen

Magnetically separable titanium dioxides (MSTs) were synthesized from nano-magnetite (Fe3O4), tetraethyl orthosilicate (TEOS), and titanium butoxide (TBT) using a sol–gel process, and their activity in the photocatalytic oxidation of ibuprofen (IBP) was evaluated. Transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) revealed that the thickness of TiO2 layers was linearly dependent on the TBT content, producing predictable results. As the ratio of TBT (mL) to TEOS (mL) increased, the purity of the TiO2 layers of the prepared MSTs increased owing to the absence of Si compounds. Based on TEM-EDS, X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses, TiO2 in MSTs was successfully coated on the surface of amorphous SiO2 with Fe3O4 as the core. Magnetization of the MSTs declined exponentially with increasing thickness of the non-magnetic SiO2–TiO2 layer. The optimal loading and activation energy of MSTs were also determined for photocatalytic removal of IBP. Comparison of the kinetic constants suggests a positive relationship between photocatalytic activity and surface area. Increased aggregation of the MSTs with higher magnetization values was attributed to stronger magnetic dipole–dipole interactions. The results of this study provide an in-depth understanding of the synthesis of magnetically separable catalysts satisfying the requirements of both magnetic separation and photocatalytic activity with potential application in the removal of recalcitrant organic pollutants.

Kinetic modelling of Escherichia coli inactivation in a photocatalytic wall reactor

A kinetic model of the photocatalytic inactivation of Escherichia coli in an annular wall reactor is presented. The model is based on a reaction scheme that involves a series of events in which bacteria are progressively damaged and eventually led to cell lysis. The model explicitly takes into account radiation absorption effects. Photocatalytic inactivation experiments were carried out in a photoreactor operated in a closed recirculating circuit with a reservoir tank and irradiated with a 6W black light lamp situated in the axis of the reactor. Immobilization of TiO2 Aeroxide P25 has been carried out by the dip-coating procedure onto the inner-tube wall of the annular reactor. Experimental results for different TiO2 layer thicknesses were used to estimate the kinetic parameters of the model. Good agreement between model predictions and inactivation experiments was achieved in the whole range of TiO2 thicknesses studied.

Design and fabrication of nanometric TiO2/Ag/TiO2/Ag/TiO2 transparent conductive electrode for inverted organic photovoltaic cells application

In this study, transparent conductive TiO2/Ag/TiO2/Ag/TiO2 (TATAT) nano-multilayer system is designed and optimum thickness of TiO2 and Ag layers are calculated. TATAT nano-multilayer films were deposited on glass substrates at room temperature by a thermal evaporation technique. We investigated some electrical, optical and structural properties of optimized TATAT multilayer such as sheet resistance, optical transmittance and the root-mean-square surface roughness. Here, we suggest a very low resistance transparent electrode (2.3(Ω/□)) with a high transmittance (90%) for optoelectronics applications. Inverted organic photovoltaic cell was fabricated on the TATAT cathode. The fabricated cell with 12nm of Ag layer shows higher power conversion efficiency (2.68%) compared to that fabricated on the ITO electrode (1.84%). The results show that the TATAT multilayer system is a suitable structure for use as transparent conductive electrode in optoelectronic devices.

Efficiency improvement of CdS and CdSe quantum dot-sensitized solar cells by TiO2 surface treatment

CdS and CdSe quantum dots (QDs) have been synthesized via successive ionic layer adsorption and reaction for the fabrication of quantum dot-sensitized solar cells (QDSSCs). In this work, several approaches such as incorporation of ZnS passivation layer, scattering layer, treatment with TiCl4, and increasing the TiO2 layer thickness have been applied on TiO2 layer in order to improve the solar cell performance. By passivating the QD-sensitized TiO2 layer with ZnS, the performance of the cells increased due to reduction of charge recombination at the photoanode/electrolyte interface. With a thicker TiO2 layer thickness of 26 μm, further enhancement was observed. The efficiency of the CdS and CdSe QDSSCs improved from 1.06% to 1.48% and from 1.41% to 3.05%, respectively. On the other hand, scattering layer and treatment with TiCl4 did not bring much improvement to the cells.

Nanosecond pulsed laser irradiation of titanium: Oxide growth and effects on underlying metal

Titanium oxide/oxynitride coatings were created on the polished surface of commercially pure, grade 2 titanium substrates by irradiating samples in air using a nanosecond-pulsed, infrared (1064nm) fiber laser. Coatings consist of three distinct layers, including a thin TiO2 rutile cap, a TiO middle layer, and an inhomogeneous bottom layer that is composed of TiOxN1−x and possibly oxygen-intercalated phases such as Ti6O. The combined thickness of TiO2 and TiO layers was varied from ~10 to 120nm by increasing the accumulated laser fluence. Laser-grown coatings exhibit different colors, which vary with oxide thickness. The observed color is attributed to the interference of incident white light reflected from the upper and lower boundaries of the TiO2 capping layer.

Enhanced performance of dye-sensitized solar cells with TiO2 blocking layers and Pt counter electrodes prepared by physical vapor deposition (PVD)

Titanium dioxide (TiO2) thin films as block layers are prepared by DC reactive magnetron sputtering. X-ray diffraction (XRD) and TEM-(SAED) analyses of the films reveal that they are polycrystalline in nature and have tetragonal structure with preferred orientation along the (101) direction. The surface morphological studies by FESEM and AFM reveal the uniform surface coverage of the grains on the surface of the films. An optical transmittance value of 80% in the visible light region with the optical band gap value of 3.2eV is measured. This sputtered TiO2 thin film is used as a blocking layer over which a thick layer of TiO2 of about 10μm was prepared using TiO2 paste and this stack is used as the photoanode of a DSSC cell. Electron beam evaporated platinum thin film on FTO coated glass substrate is used as counter electrode. The performance of the cell with a Voc of 0.698V, a Jsc of 6.8 mAcm−2 and an efficiency of 4.2% was achieved

Nanoimprinted distributed feedback lasers comprising TiO2 thin films: Design guidelines for high performance sensing

AbstractDesign guidelines for optimizing the sensing performance of nanoimprinted second order distributed feedback dye lasers are presented. The guidelines are verified by experiments and simulations. The lasers, fabricated by UV‐nanoimprint lithography into Pyrromethene doped Ormocomp thin films on glass, have their sensor sensitivity enhanced by a factor of up to five via the evaporation of a titanium dioxide (TiO2) waveguiding layer. The influence of the TiO2 layer thickness on the device sensitivity is analyzed with a simple model that accurately predicts experimentally measured wavelength shifts induced by varied superstrate refractive indices. The superstrate refractive index is additionally shown to determine which of the possible waveguiding modes dominates for lasing, indicating a method to flexibly select the polarization of the laser. The detection limit of the sensor system is further discussed, finding an optimum at 7.5· 10−6 RIU. Wavelength changes caused by dye bleaching must be taken into account for long‐term measurements.

Complementary co-sensitization of an aggregating squaraine dye in solid-state dye-sensitized solar cells

In this study, we used the co-sensitization approach to reach panchromatic light absorption in solid-state dye-sensitized solar cells (SDSCs). We combined two complementary absorbing organic sensitizers, viz. a blue-absorbing triphenyldiamine dye (TPD-dye) and a red-absorbing squaraine dye (SQ-dye). The aggregation behaviour of SQ-dye was entirely investigated by steady-state UV/vis spectroscopy. The formation of H- and J-aggregates was observed in both solution and the chemisorbed state on mesoporous TiO2. On applying SQ-dye and TPD-dye in single-dye and co-sensitized SDSCs, the external quantum efficiency studies clearly indicate that TPD-dye, as well as the monomer species and the H- and J- aggregates of SQ-dye contribute to the current generation. We optimized the performance of the co-sensitized SDSCs regarding the solvent used for the chemisorption, the chemisorption time, and the thickness of the mesoporous TiO2 layer. The best result was obtained for a co-sensitized SDSC after chemisorption for 3 h from a tert-butanol/acetonitrile 1:1 solution using a 1.4 μm thick mesoporous TiO2 layer.

Optimization of black dye-sensitized solar cells by numerical simulation

The numerical simulation of the physical parameters for dye sensitized solar cells with black dyes was considered based on a new optimizing procedure. The influence of thickness and lifetime on the J−V characteristics parameters was analyzed. In this way, Jsc (short-circuit current density), Voc (open circuit voltage), FF (fill factor), and η (efficiency) were determined. A comparison between the classical ruthenium based solar cells and black dyes ones was possible on the simulation and experimental approach. The obtained optimum values for thickness and lifetime, as well as the analysis of the main parameters of the J−V characteristics of black-dye solar cells, could be used to optimise the manufacturing process. The electron lifetime is in the range of 2–100 ms and has its optimal value of 15 ms. The suitable thickness of TiO2 layer was determined to be in the range of 8–20 μm with the optimal value of 10 μm, where Jsc and η reach their maxima.

Titanium dioxide nanofibers integrated stainless steel filter for photocatalytic degradation of pharmaceutical compounds

A photocatalytically active stainless steel filter (P-SSF) was prepared by integrating electrospun TiO2 nanofibers on SSF surface through a hot-press process where a poly(vinylidene fluoride) (PVDF) nanofibers interlayer acted as a binder. By quantifying the photocatalytic oxidation of cimetidine under ultraviolet radiation and assessing the stability of TiO2 nanofibers integrated on the P-SSF against sonication, the optimum thickness of the TiO2 and PVDF layer was found to be 29 and 42μm, respectively. At 10L/m2h flux, 40–90% of cimetidine was oxidized when the thickness of TiO2 layer increased from 10 to 29μm; however, no further increase of cimetidine oxidation was observed as its thickness increased to 84μm, maybe due to limited light penetration. At flux conditions of 10, 20, and 50L/m2h, the oxidation efficiencies for cimetidine were found to be 89, 64, and 47%, respectively. This was attributed to reduced contact time of cimetidine within the TiO2 layer. Further, the degradation efficacy of cimetidine was stably maintained for 72h at a flux of 10L/m2h and a trans-filter pressure of 0.1–0.2kPa. Overall, our results showed that it can potentially be employed in the treatment of effluents containing organic micropollutants.

Structural and optical studies of nanostructured TiO2–Ge multi-layer thin films

This paper reports the effects of annealing on structural and optical properties of nanostructured multi-layer TiO2–Ge thin films. These films were characterized using different techniques such as X-ray diffraction, X-ray reflectivity, Rutherford backscattering (RBS), and Fourier Transform Infrared spectroscopy. Annealing was responsible for pronounced changes in structural and optical properties of these films, as associated with changes in their structures, stoichiometry and stress-state.Three sets of TiO2–Ge multi-layer films were deposited by electron beam evaporation and resistive heating with different Ge layer thickness (5, 10 and 15nm), and TiO2 layer thickness was fixed to 20nm. The films were annealed in air up to 500°C for 2h. RBS studies showed that the layer structure of TiO2–Ge multi-layer films had been formed. The absorption spectra and band gap energy showed a blue shift with decrease in Ge layer thickness. The absorption spectra of these films suggest quantum confinement that increases with annealing temperature before the complete oxidation of Ge. Apparently complete oxidation results in sudden or sharp rise in band gap energy that matches with that of TiO2. RBS study reveals that layered structure of TiO2–Ge multi-layer films is not destroyed by annealing, which may be due to non-wetting behavior of Ge and its oxide with TiO2. These results imply that nanostructured TiO2–Ge multi-layer thin films may be employed as heterojunctions (with tunable band gap energy) based on quantum confinement effects for use in photovoltaics.

Preparation and properties of ATO films and their effects on the TiO2/ATO system

Multilayered TiO2/ATO thin films were prepared by the spin-coating method to evaluate the electronic interactions and the effect of the experimental conditions on optical transparency, electric resistivity and carrier density. ATO chemical composition, number of layers and annealing temperature were modified to study their effect on the global properties of the TiO2/ATO system. TiO2/ATO films exhibited an optical transparency as high as 81 % in the visible wavelength and a strong absorption within the UV spectra. Electric resistivity as low as 3.4 × 10−1 Ω·cm was measured for TiO2/ATO films. Optical properties were influenced mainly by the presence of upper TiO2 layer and ATO film thickness. The effect of ATO film thickness, composition and annealing temperature on TiO2/ATO transparency and resistivity are discussed.