Thickness Of TiO2 Layer Research Articles

High-Efficiency Perovskite Solar Cell Based on Poly(3-Hexylthiophene): Influence of Molecular Weight and Mesoscopic Scaffold Layer.

Here, we investigated the effect of the molecular weight (MW) of poly 3-hexylthiophene (P3HT) hole-transport material on the performance of perovskite solar cells (PSCs). We found that by increasing the MW the photovoltaic performances of the cells are enhanced leading to an improvement of the overall efficiency. P3HT-based PSCs with a MW of 124 kDa can achieve an overall average efficiency of 16.2 %, double with respect to the ones with a MW of 44 kDa. Opposite to spiro-OMeTAD-based PSCs, the photovoltaic parameters of the P3HT-based devices are enhanced by increasing the mesoporous TiO2 layer thickness from 250 to 500 nm. Moreover, for a titania scaffold layer thickness of 500 nm, the efficiency of P3HT-based PSCs with high MW is larger than the spiro-OMeTAD based PSCs with the same scaffold layer thickness. Recombination reactions of the devices were also investigated by voltage decay and electrochemical impedance spectroscopy. We found that the relationship between P3HT MW and cell performance is related to the reduction of charge recombination and to the increase of the P3HT light absorption by increasing the MW.

Impact of Film Thickness of Ultrathin Dip-Coated Compact TiO2 Layers on the Performance of Mesoscopic Perovskite Solar Cells.

Uniform and pinhole-free electron-selective TiO2 layers are of utmost importance for efficient perovskite solar cells. Here we used a scalable and low-cost dip-coating method to prepare uniform and ultrathin (5-50 nm) compact TiO2 films on fluorine-doped tin oxide (FTO) glass substrates. The thickness of the film was tuned by changing the TiCl4 precursor concentration. The formed TiO2 follows the texture of the underlying FTO substrates, but at higher TiCl4 concentrations, the surface roughness is substantially decreased. This change occurs at a film thickness close to 20-30 nm. A similar TiCl4 concentration is needed to produce crystalline TiO2 films. Furthermore, below this film thickness, the underlying FTO might be exposed resulting in pinholes in the compact TiO2 layer. When integrated into mesoscopic perovskite solar cells there appears to be a similar critical compact TiO2 layer thickness above which the devices perform more optimally. The power conversion efficiency was improved by more than 50% (from 5.5% to ∼8.6%) when inserting a compact TiO2 layer. Devices without or with very thin compact TiO2 layers display J-V curves with an "s-shaped" feature in the negative voltage range, which could be attributed to immobilized negative ions at the electron-extracting interface. A strong correlation between the magnitude of the s-shaped feature and the exposed FTO seen in the X-ray photoelectron spectroscopy measurements indicates that the s-shape is related to pinholes in the compact TiO2 layer when it is too thin.

Mechanistic insights into TiO2 thickness in Fe3O4@TiO2-GO composites for enrofloxacin photodegradation

Multifunctional Fe3O4@TiO2-GO (FTG) magnetic composites have extensive application potential. However, the effect of TiO2 shell thickness as well as its underlying mechanism remains murky and motivates our study. Herein, FTG composites with the optimized TiO2 shell thickness were synthesized. The characterization results show that the FTG photocatalysts had the advantages of easy magnetic separation, extended light absorption range (>600nm), and efficient charge separation properties. The photocatalytic activity of FTG was performed for photo-degradation of enrofloxacin (ENR) under visible light. The FTG composites with TiO2 layer thickness of 17nm exhibited the highest photocatalytic activity, and significant recycle efficiency. The photocatalytic mechanism, as characterized using electrochemistry, ESR, and in-situ QXAFS analysis, indicates that this optimal TiO2 shell thickness delicately balances the generation and effective transport of electrons, and therefore is optimal for the production of hydroxyl radicals. This study provides new insights into the fabrication of TiO2-based materials and their photocatalytic application.

Influence of TiO2‐Layer Thickness of Spray‐Coated Glass Beads on Their Photocatalytic Performance

AbstractTiO2 is a suitable catalyst for potential photocatalytic processes, e.g., in wastewater treatment. For a technical realization of such processes, the application of immobilized TiO2 in a continuous process would be desirable. However, since UV radiation has a limited penetration depth into a packed bed of pure TiO2, supporting it on UV‐transparent glass beads offers the possibility to implement continuous photocatalytic processes in a fixed‐bed reactor. Considering this fact, glass beads were coated with TiO2 powder in a fluidized‐bed reactor. The coated glass beads with varying TiO2 layer thickness were tested in the photocatalytic degradation of methylene blue, and the influence of an addition of methyl cellulose during the coating process on the photocatalytic performance was investigated.

Composite Tin Dioxide-Titanium Dioxide Nanostructured Thin Film Electrodes As Lithium-Ion Anodes

An aerosol-chemical vapor deposition technique (ACVD) was utilized in order to deposit highly oriented, one-dimensional nanostructured metal-oxide thin films. Film morphology was controlled using various system parameters in order to obtained the desired columnar morphology. Tin dioxide (SnO2) was chosen as an electrode material due to its high theoretical charge capacity (790 mA-h-g-1), and titanium dioxide (TiO2) was chosen for its remarkable stability and low volume change during charging. The columnar morphology is particularly well suited to SnO2 as the space between the columns allows for accommodation of the large volume expansion the material experiences during charging. Electrodes of SnO2 columnar nanostructures were first synthesized using ACVD by depositing the structures directly on to the current collector. Depositing directly onto the current collector eliminates the need for binding agents and conductive additives during battery fabrication. Then a layer of TiO2 was deposited on the surface of the SnO2 columns using atomic layer deposition. A variety of column heights, ranging from 500 nm to 2 um, and TiO2 layer thickness, ranging from no TiO2 to a 100 nm layer, were synthesized and their electrochemical properties investigated. For all electrochemical characterization experiments, Swagelok-type coin cells were fabricated using lithium foil as a counter electrode and 1M LiPF6 in 50/50 (v/v) EC/DEC as an electrolyte. Optimal electrochemical performance was observed in electrodes with a height of 800 nm and a 15 nm layer of TiO2. A rate capability test was performed to determine how the capacity of the electrodes changed at charging rates ranging from 100-2000 mA-g-1. A stable capacity of 410 mA-h-g-1 was obtained at a charge rate 1000 mA-g-1; rapid capacity fade was observed at higher rates. Galvanostatic charge-discharge was performed for each cell for 100 cycles or until failure at a charge rate of 400 mA-g-1, corresponding approximately to a charge rate of C/2. For the optimal electrode an initial irreversible capacity of 1164 mA-h-g-1 was observed as well as a stable capacity of 530 mA-h-g-1 after 100 cycles. This demonstrates a low cost synthesis of high performance anodes which provides an alternative to conventional electrode synthesis.

Effect of thickness and microstructure of TiO2 shell on photocatalytic performance of magnetic separable Fe3O4/SiO2/mTiO2 core‐shell composites

Here, unique Fe3O4/SiO2/mTiO2 (FST) composites were fabricated, which are composed of a Fe3O4 core with a strong response to magnetic field, an intermediate SiO2 layer as an electronic barrier, and an outer mesoporous TiO2 (mTiO2) as the active layer for degradation of organic contaminants. The distinctive approach involved TiO2 shell coating on the surface of Fe3O4/SiO2 (FS) particle using a sol–gel method, followed by the crystallization and mesopore‐formation of TiO2 through solvothermal treatment. By changing the dosage of tetrabutyl titanate (TBOT), the thickness and microstructure of TiO2 layer were regulated. Among all as‐prepared FST composites, the FST composite that was prepared with 0.6 ml TBOT (FST‐0.6) possessed a good microstructure and a large specific surface area, and exhibited superior photocatalytic activity toward the degradation of methylene blue (MB) solution. Moreover, recovered FST‐0.6 composite with the help of an appropriate magnetic field maintained the activity without significant decline during multiple photocatalytic tests. Accordingly, a rational mechanism was proposed to explain why the FST‐0.6 composite showed excellent photocatalytic performance.

Consecutive anchoring of symmetric viologens: Electrochromic devices providing colorless to neutral-color switching

In this study, colorless to neutral-grayish color ECDs based on the consecutive anchoring of alkyl-substituted and aryl substituted symmetric viologens (blue and green switching vilogens respectively) are reported.The strong binding affinity towards nanostructured TiO2 layer of both viologens equally provided with phosphonate anchoring group, allows the employment of a single nanostructured layer wherein both viologens were adsorbed (glass/TCO/viologens-modified-TiO2/TCO/glass), while showing very rapid anchoring times (≤15min).The effect of the TiO2 layer thickness and grafting conditions on the ECD performance have also been investigated, reaching switching times ≤6s and good performance up to 2000 cycles for the optimized ECDs. Additionally, the influence of the electrolyte on the observed coloration has also been explored. The use of water-based gel polyelectrolyte has allowed significant enhancement of the neutral-grayish EC behavior (a* and b*≤ |10|). The beneficial impact of water-based gel polyelectrolyte and potential in color-tailored electrochromics is emphasized.

Improving transparency in dye-sensitized nanostructured solar cells by optimizing nano-porous titanium dioxide photo-electrode

Today’s the technology based on dye-sensitized solar cells (DSSCs) has an important role in all photovoltaic system technologies. DSSCs can generate electricity with various degrees of transparency; this makes it suitable for use in various industries, especially in construction industry as smart windows. In fact DSSC can produce electricity and having natural light, simultaneously. It is obvious that DSSCs need to absorb solar radiation as much as possible. Since, the effective use of all incident lights leads to an increase in cell efficiency and this increase in efficiency is related to the amount of dye adsorbed on the surface of nanostructured electrode, so higher amount of dye for higher efficiency tends to the reduction of transparency of the cell. This paper has been attempted to investigate the relationship between these two parameters of transparency and efficiency for DSSCs by maintaining the cell stability in a long-term time interval. The results showed that the thickness of the nano-porous titanium dioxide film and the size of its nanoparticles have an important role as the photo-anode due to the absorption of the dye molecules in the DSSCs. Using the smallest size of TiO2 nano-particles in the anatase phase, and optimizing the TiO2 layer thickness by adding terpineol solvent in it, the stability of the DSSC is improved exceedingly and the level of transparency increased from 30.43 to 46.5% with maintaining the efficiency of the 3.2%. Besides, we used a new two-step method to fabricate higher performance cells and the efficiency increased to 3.78 with saving its 46.5% transparency. Results indicate that other parameters like using different electrolytes and different deposition methods of platinum counter electrode have lower effects in this optimization compared to the photo-anode effect.

Режим сверхбыстрого атомного транспорта и другие процессы в сплаве титана, модифицированого ионной и циклической термической обработкой

In this work we study the formation of a relatively thick TiO2 layer on the surface of Ti-6Al-4V alloy after ion-thermal treatment (IThT). A stoichiometric composition closed to the TiO2 layer, its depth, and local oxidation anisotropy were detected by micro-RBS. Anisotropic oxidation observed at some local areas near the SIMS craters. In this work, a possible mechanism of the oxide layer formation and thermal stability of spherical inclusions size will be discussed in connection with the superfast 18O implant migration and it dissolution at elevated temperatures. It supposed that dielectric spherical inclusions compose from the particles of about few of tenth nanometers in grain size.

Optical Optimization of Perovskite Solar Cell Structure for Maximum Current Collection

High conversion efficiency has been recently demonstrated for Perovskite thin film photovoltaic devices. Perovskite thin film solar cells are multilayer opto-electrical structures in which light interference occurs. This phenomenon can be used to maximise the light transmission into the absorber material and increase the device efficiency. Fine tuning of the layer thicknesses within the stack can be used to control interference at the interfaces. Optical reflection losses can be reduced by achieving destructive interference within the structure of the cell. The light transmission to the Perovskite absorber of a thin film solar cell on a fluorine doped tin oxide transparent conductor has been modelled using the transfer matrix method. Alternative transparent conductor materials have been also investigated including AZO and ITO. The modelling showed that replacing FTO with ITO could increase the photocurrent by as much as 4.5%. The gain can be further increased to 6.5% by using AZO as the TCO material. Fine tuning of the TiO2 layer thickness can increase the current density by 0.3%. Furthermore, the current density of a Perovskite solar cell can be increased by application of a multilayer anti-reflective coating by another 3.5%. Optical optimisation of the stack design offers a significant increase in conversion efficiency.

Inkjet printing of high refractive structures based on TiO2 sol

Subject of Research. The paper deals with description of novel inkjet printing method for optical elements formed by structures based on TiO2 sol. The proposed approach presents effective way to obtain such optical nano objects as diffraction structures and transparent interference patterns. Methods. TiO2 nanoparticles were synthesized by hydrolysis of titanium isopropoxide (0.36 mol) in deionized water (33.3 mol) under vigorous stirring and using nitric acid (0.04 mol) as a protonating agent. Viscosity was determined by Brookfield HA/HB viscometer, and surface tension - by Kyowa DY-700 tensiometer. Titanium dioxide inks were deposited on commercially available microembossed PET film with a thickness of 20 µm. To print titania ink Canon Pixma IP 2840 desktop office printer was used with a drop volume of 2 pL. The thickness of an inkjet TiO2 layer after drying in the air and removal of the solvents did not exceed 500 nm with a refractive index not less than 2.08 in the entire visible range.Main Results. The synthesis of aqueous TiO2 sol was used to obtain the ink with desirable rheological characteristics: viscosity and surface tension. The required rheology was regulated by controlling parameters of sol-gel transition in the system of aqueous titanium dioxide sol and by adding ethanol that affects the charge of double electrical layer of disperse phase. The reviled ratio of titanium dioxide sol and ethanol in the system gives such values of viscosity and surface tension that make this material convenient for inkjet printing. The coatings created by sol have a high refractive index in the entire visible range (not less than 2.08). We have shown that the deposition of optical transparent microstructures with diffraction effect has an ability to be applied on the transparent surfaces. The morphology of particles and the topology of printed structures were analyzed by optic and atomic-force microscopes.Practical Relevance. We have proposed the approach to obtain colorful interference patterns using one type of high refractive inks. The method opens new opportunities for “roll-to-roll” production technology of protected optical structures on the flexible polymer substrates.

Ellipsometric porosimetry on pore-controlled TiO2 layers

The practical performance of surface coatings in applications like catalysis, water splitting or batteries depends critically on the coating materials’ porosity. Determining the porosity in a fast and non-destructive way is still an unsolved problem for industrial thin-films technology. As a contribution to calibrated, non-destructive, optical layer characterisation, we present a multi-method comparison study on porous TiO2 films deposited by sol-gel synthesis on Si wafers. The ellipsometric data were collected on a range of samples with different TiO2 layer thickness and different porosity values. These samples were produced by templated sol-gel synthesis resulting in layers with a well-defined pore size and pore density. The ellipsometry measurement data were analysed by means of a Bruggeman effective medium approximation (BEMA), with the aim to determine the mixture ratio of void and matrix material by a multi-sample analysis strategy. This analysis yielded porosities and layer thicknesses for all samples as well as the dielectric function for the matrix material. Following the idea of multi-method techniques in metrology, the data was referenced to imaging by electron microscopy (SEM) and to a new EPMA (electron probe microanalysis) porosity approach for thin film analysis. This work might lead to a better metrological understanding of optical porosimetry and also to better-qualified characterisation methods for nano-porous layer systems.

Effect of screen printing type on transparent TiO2 layer as the working electrode of dye sensitized solar cell (DSSC) for solar windows applications

The working electrode based on semiconductor TiO2 DSSC has been fabricated by screen printing method. This study aim is to determine the effect of the screen type on TiO2 layer as the working electrode of DSSC. Screen used for deposition of TiO2 has the types of; T- 49, T-55 and T-61. TiO2 layer was sintered at temperature of 500°C. DSSC structure was composed of semiconductor TiO2 adsorbed dye, an electrolyte solution and a platinum counter electrode. TiO2 layer thickness was characterized by Scanning Electron Microscopy (SEM), while the absorbance was characterized using UV-Vis spectrophotometer and the electrical properties of DSSC were characterized by Keithley I-V measurement. TiO2 layer fabricated by screen T-49 had the biggest thickness that was 3.2 ± 0.3 μm and the highest UV-Vis absorbance wave at the peak wavelength of 315 nm with the absorbance value was 1.7. The I-V characterization showed that the sample fabricated by screen T-49 obtained the greatest efficiency that was 1.0 × 10-1%

Long-term corrosion tests of Ti3SiC2 and Ti2AlC in oxygen containing LBE at temperatures up to 700 °C

Two MAX-phase materials, Ti3SiC and Ti2AlC, were tested at 550 °C, 650 °C and 700 °C up to 10 000 h in LBE (lead-bismuth-eutectic) containing of 10−6 and 10−8 wt% oxygen. It was found that secondary phases have a strong influence on corrosion effects. Ti3SiC showed a surface disintegration at 550°C/10−6 wt% oxygen after longer exposure, while a 4–7 μm thick TiO2 layer with Pb-Bi inclusions was detected on Ti2AlC. However, Ti3SiC is protected by a double layered oxide with an outer part of TiO2 and a mixed inner layer of SiO2 and TiO2 at the higher temperatures. Ti2AlC formed a TiO2 surface layer containing Al2O3. Some defects could be observed on the Ti3SiC surface in LBE containing 10−8 wt% oxygen at 550 °C and 650 °C. The secondary phases between the Ti3SiC grains showed strong oxidation at 700 °C. Due to the high Al solubility in LBE, Ti2AlC experienced strong dissolution attack after longer exposure times at 650 and 700 °C.

Plastic electrochromic devices based on viologen-modified TiO2 films prepared at low temperature

In this study, flexible plastic electrochromic devices (ECDs) based on viologen-modified TiO2 nanostructured films thermally treated at only 120°C are reported. Even if a sintering process at typically above 450°C was avoided, the resulting mesoporous TiO2 films were highly transparent on both TCO-coated glass and plastic substrates while presenting adequate conductivity and high active surface area suitable for anchoring electro-chromophores. The synthesis of a viologen specifically designed to provide colorless-to-blue switching while being more compatible with plastic substrates than the traditional ethyl viologen is reported as well. The effect of the TiO2 layer thickness and pore characteristics as well as the grafting time on the device performance were also investigated. Transparent ECDs based on these viologen-modified TiO2 films have been assembled on flexible plastic substrate (ITO/PET) offering transmittance changes (ΔT) above 60% and switching speeds of 6–8s. The change in transmittance is further enhanced up to 71% in dual ECDs using PB on ITO/PET as the counter electrode and viologen-modified TiO2 films on FTO/glass. Finally, operational large-area all-solid devices (40cm×30cm) are presented, demonstrating the suitability of the present technology for the production of large-area plastic ECDs.

The optimal TiO2/Ag/TiO2 electrode for organic solar cell application with high device-specific Haacke figure of merit

As a promising indium-free electrode, transparent composite electrode (TCE) TiO2/Ag/TiO2 is an attractive alternative to indium tin oxide (ITO). The multilayer structure of TiO2/Ag/TiO2 is deposited on glass substrate by room-temperature sputtering. The effects of deposition rate, thickness of Ag and TiO2 layers on the electrical and optical properties of this TCE are presented. Results show that the Ag films tend to have fewer voids to form, if the Ag deposition rate is sufficiently high. The presence of fewer voids in the Ag layer results in higher transmittance and lower sheet resistance of the corresponding TiO2/Ag/TiO2 structure. In order to increase the solar input to the P3HT:PC61BM organic solar cell, the layer thicknesses of TiO2/Ag/TiO2 electrodes are theoretically and then experimentally optimized, such that its optical transmittances are maximized across the wavelength range where the light absorption of P3HT:PC61BM is highest. In this study, the device-specific Haacke figure of merit (FOM) of the TiO2/Ag/TiO2 electrode is optimal with the use of 42nm TiO2 layers and 10nm Ag layer. This optimal Haacke FOM is two times higher than that of ITO electrodes. The conventional bulk heterojunction organic solar cell (OSC) fabricated on optimized TiO2/Ag/TiO2 electrode shows high power conversion efficiency (PCE), almost 100% higher than PCE of OSC fabricated on ITO. Our finding indicates that TiO2/Ag/TiO2 electrode can be specifically tailored to particular applications. It can be implemented in organic solar cell and has considerable potential to replace ITO in solar cell applications.

Secondary ion mass spectrometry study of the formation of a nanometer oxide film on a titanium nitride surface

Using secondary ion mass spectrometry, we investigate the oxidation of titanium nitride films fabricated by reactive magnetron sputtering under specific conditions of burning plasma in the argon and oxygen mixture in a vacuum chamber of a magnetron sputtering facility at annealing temperatures ranging from 350 to 440°С and times ranging from 2 to 11 min. It is shown that the oxidation is activated by the plasma, while thermal activation plays a secondary role. The oxide layer consists of the TiO2 layer and (3–5)-nm-thick intermediate layer between it and the bulk of titanium nitride, which is homogeneous over the sample surface and enriched with oxygen-containing complexes. The titanium dioxide layer thickness lies within 2–3.5 nm and depends on the annealing conditions. The effect of different factors on the layer thicknesses is investigated. The expression is obtained that satisfactorily describes the dependence of the TiO2 layer thickness on annealing temperature and time.

Designing the Color of Hot-Dip Galvanized Steel Sheet Through Destructive Light Interference Using a Zn-Ti Liquid Metallic Bath

The color of hot-dip galvanized steel sheet was adjusted in a reproducible way using a liquid Zn-Ti metallic bath, air atmosphere, and controlling the bath temperature as the only experimental parameter. Coloring was found only for sample s cooled in air and dipped into Ti-containing liquid Zn. For samples dipped into a 0.15 wt pct Ti-containing Zn bath, the color remained metallic (gray) below a 792 K (519 C) bath temperature; it was yellow at 814 K, violet at 847 K, and blue at 873 K. With the increasing bath temperature, the thickness of the adhered Zn-Ti layer gradually decreased from 52 to 32 micrometers, while the thickness of the outer TiO2 layer gradually increased from 24 to 69 nm. Due to small Al contamination of the Zn bath, a thin (around 2 nm) alumina-rich layer is found between the outer TiO2 layer and the inner macroscopic Zn layer. It is proven that the color change was governed by the formation of thin outer TiO2 layer; different colors appear depending on the thickness of this layer, mostly due to the destructive interference of visible light on this transparent nano-layer. A complex model was built to explain the results using known relationships of chemical thermodynamics, adhesion, heat flow, kinetics of chemical reactions, diffusion, and optics.

Influence of grain size and microstructure on oxidation rate and mechanism in sintered titanium carbide under high temperature and low oxygen partial pressure

Titanium carbide (TiC) pellets were prepared by Spark Plasma Sintering (SPS). Three different microstructures were synthesized with average grain sizes of 340nm, 1.34μm and 25μm, respectively. Prior to oxidation treatment, TiC samples were implanted with xenon ions. This noble gas is used as a marker of the initial surface. Oxidation behavior was studied by Rutherford Backscattering Spectroscopy (RBS) and electronic microscopy through thermal treatment at 1000°C for 10h and under different low oxygen partial pressure (OPP). No detectable oxidation was observed after thermal treatment at OPP≤2.10−7mbar whereas an oxide layer is formed at OPP=2.10−6mbar. Thickness, composition and morphology of the oxide layer depend on the initial microstructure of the material. Numerous grain boundaries and the porosity (≈10%) of the nano-grained material were responsible for the enhanced penetration of oxygen which resulted in the formation of a thick oxide layer. This layer is composed of external oxide and interfacial band sublayers. Ti4O7 was identified by XRD (X-Ray Diffraction) as being the main phase in the oxide layer concerning the nano-grained material whereas a relatively thick layer of TiO2 (rutile) is formed for larger grain microstructures. We proved the presence of carbon in the interfacial band as well as possible evacuation paths for CO/CO2 gas. There is less release of xenon from nano-grained material than larger grained materials during oxidation at OPP=2.10−6mbar for 20h attesting to the superior gas-tightness of the oxide layer in this case. A schematic model is then proposed to explain growth mechanisms and properties of the oxide layer.

Well-Organized Mesoporous TiO2 Photoanode by Using Amphiphilic Graft Copolymer for Efficient Perovskite Solar Cells

The control of the thickness and porosity of a mesoporous TiO2 layer is important to improve the photovoltaic performance of perovskite solar cells. We produced organized mesoporous TiO2 (om-TiO2) layers using a low-cost amphiphilic graft copolymer, poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM), as a sacrificial template. This simple but effective synthetic approach generates highly mesoporous and well-organized TiO2 nanostructures with interconnected and size-tunable features. Specifically, the average pore size increased with the amount of hydrophobic PVC main chain in the graft copolymer, which acted as the pore forming agent. Perovskite layers were prepared on top of an om-TiO2 layer according to a two-step sequential deposition: after coating the PbI2 solution in dimethylformamide (DMF) on an om-TiO2 substrate, the substrate was prewetted in isopropyl alcohol (IPA) solvent before immersing into a CH3NH3I/IPA solution. This prewetting treatment not only improves the yields of ...