Spin-coated Films Research Articles

Mixed tin-lead perovskite nanorod-based resistive memory device

• Perovskite nanorods synthesis by intercalation of long-chain organic cations. • Use of oleylammonium organic cation into bulk methylammonium tin-lead bromides as cations. • Poly(methyl methacrylate) encapsulated nanorods are excellent memristor active layer. SET voltage lowered to ∼ 0.5 V and ON OFF current ratios enhanced to ∼10 5 . Stable mixed cation (tin-lead) perovskite nanorods results from intercalating long-chain organic ligand- oleylamine into perovskite 3D (CH 3 NH 3 PbBr 3 ) structure using the ligand-assisted re-precipitation method. A spin-coated nanorod film works as an active layer for resistive memory devices by sandwiching nanorod film between two electrodes with a switching voltage of 1.4 V. A poly(methyl methacrylate) passivated nanorod film results in better resistive memory properties by exploiting advantages of both insulating poly(methyl methacrylate) and semiconducting perovskite nanorods. The passivation enhances the stability of the device, protecting electrodes from reacting with the perovskite layer. The structure lowers the current in the high resistance state, increasing the ON OFF current ratio to ∼ 10 5 . The device exhibits non-volatile rewritable resistive switching characteristics with a switching voltage ∼ 0.5 V. The conduction mechanism involved in the switching action is explained from the relation between current-voltage as space charge limited conduction.

Relaxation of externally strained halide perovskite thin layers with neutral ligands

<h2>Summary</h2> The preferred orientation (PO) and non-uniform strain of the perovskite layer coated on the substrate can cause unwanted blue shifts in the band gap and several defects inside and on the grain boundaries. Therefore, suppressing the anisotropic preferred growth of halide perovskite crystals while satisfying the trap passivation of grain boundaries is important to the fabrication of efficient and stable perovskite solar cells (PSCs). In this study, the properties of spin-coated perovskite thin films were investigated by adding an appropriate amount of trioctylphosphine (TOP) as a neutral ligand to a formamidinium lead triiodide (FAPbI₃) precursor solution. The TOP in the FAPbI₃ precursor solution containing MACl significantly alleviated the PO by MACl and further induced a redshift of the band gap through the reduction of microstrain. Furthermore, TOP contributed to the passivation of defects via the surface termination of grain boundaries. PSCs based on these perovskite thin films exhibited an efficiency close to 25%.

Influence of Airflow Disturbance on the Uniformity of Spin Coating Film Thickness on Large Area Rectangular Substrates

Spin coating is widely used to form a uniform film on a solid substrate. Airflow disturbance has been considered as one of the most influential factors of film thickness, especially for spin coating on large area noncircular substrates. However, the exact mechanism of airflow disturbance influence, such as air shear force effect or indirect effects on evaporation, so far, remains ambiguous. In this work, the influence mechanism of airflow disturbance on film uniformity on large rectangular substrates is studied. The experiment with airflow disturbance is artificially introduced and contrasts with the common spin coating conditions. Both numerical simulations and experiments show a causal relationship between airflow disturbances and the uniformity of the spin coating film. The film thickness and airflow field results show that the film uniformity is affected by solvent evaporation and air shear force caused by airflow disturbance. Additionally, evaporation inhibition and airflow disturbance results do not support the proposition that air shear forces can affect film uniformity, but that solvent evaporation is the primary factor affecting film thickness uniformity. These conclusions are beneficial to the understanding of the mechanism of airflow disturbance influence on the film thickness uniformity on large rectangular substrates.

In-depth analysis of the photophysics of BOPAHY dyes in solution, glass and film

BOPAHY dyes are a recently synthesized class of asymmetric highly fluorescent double boron complexed dyes. The photophysics of 5-substituted BOPAHY dyes was investigated by steady-state and time-resolved spectroscopy in liquid solution, dissolved in an organic glass and in neat spin-coated films. In the latter samples some derivatives show efficient fluorescence. The experimental results were compared with the predictions from DFT and time dependent DFT. The influence of the nature of the hetero-aromatic substituent in the 5-position on the features of the absorption and fluorescence spectra and the decay of the S1-state is linked to the molecular morphology. The experiments show the choice of the 5-substituent is critical to avoid loss of a boron center in solution.

Effect of Zn and Sn incorporation on the crystallinity of spin-coated CuInSe2 thin films

Effect of Zn and Sn incorporation on the crystallinity of spin-coated CuInSe2 thin films

Annealing effect on thermoelectric characteristics of Spin-coated Cu2Se nanoparticle thin films

In this study, we fabricated a spin-coated Cu2Se nanoparticle (NP) thin film on a plastic substrate and investigated the effects of low-temperature annealing on its thermoelectric characteristics. After thermal annealing at 150 ℃ for 10 min in vacuum, the electrical conductivity of the Cu2Se NP thin film was dramatically enhanced from 1.05 × 102 to 2.09 × 104 S/m, whereas its thermal conductivity slightly increased from 0.11 to 0.50 W/m∙K. The power factor and the figure of merit of the annealed Cu2Se NP thin films at room temperature in air was 25.6 μW/m∙K2 and 1.54 × 10−2, respectively.

Asymmetric AZA-BODIPY with Optical Gain in the Near-Infrared Region.

In recent years, there has been a lot of interest in the development of organic compounds emitting in the near-infrared (NIR) region due to their stimulating applications, such as biosensing and light detection and ranging (LiDAR). Moreover, a lot of effort has been devoted to finding organic emitters with optical gain in the NIR region for lasing applications. In this paper, we present the ultrafast spectroscopy of an asymmetric AZA-BODIPY molecule that shows relevant photophysical changes moving from a diluted solution to a concentrated solution and to a spin-coated film. The diluted solution and the spin-coated film show a bleaching band and a stimulated emission band in the visible region, while the very concentrated solution displays a broad (150 nm) and long-living (more than 400 ps) optical gain band in the NIR region, centered at 900 nm. Our results pave the way for a new organic laser system in a near-infrared spectral region.

Low-resistivity Pd nanopatterns created by a direct electron beam irradiation process free of post-treatment steps

The ability to create metallic patterned nanostructures with excellent control of size, shape and spatial orientation is of utmost importance in the construction of next-generation electronic and optical devices as well as in other applications such as (bio)sensors, reactive surfaces for catalysis, etc. Moreover, development of simple, rapid and low-cost fabrication processes of metallic patterned nanostructures is a challenging issue for the incorporation of such devices in real market applications. In this contribution, a direct-write method that results in highly conducting palladium-based nanopatterned structures without the need of applying subsequent curing processes is presented. Spin-coated films of palladium acetate were irradiated with an electron beam to produce palladium nanodeposits (PdNDs) with controlled size, shape and height. The use of different electron doses was investigated and its influence on the PdNDs features determined, namely: (1) thickness of the deposits, (2) atomic percentage of palladium content, (3) oxidation state of palladium in the deposit, (4) morphology of the sample and grain size of the Pd nanocrystals and (5) resistivity. It has been probed that the use of high electron doses, 30000 μC cm−2 results in the lowest resistivity reported to date for PdNDs, namely 145 μΩ cm, which is only one order of magnitude higher than bulk palladium. This result paves the way for development of simplified lithography processes of nanostructured deposits avoiding subsequent post-treatment steps.

Integration of biocompatible Coomassie Brilliant Blue dye on silicon in organic/Inorganic heterojunction for photodetection applications

Here, we introduce systematic investigations of structural, morphological, and optical properties of solution-processed coomassie brilliant blue, CBB, thin films for photodetection applications. First, the structural and morphological features of the spin-coated CBB thin films are investigated using XRD and FESEM microscopy and yielded a polycrystalline, nanostructured, and porous CBB film of crystallite size and RMS roughness ∼31.95 nm and 10.65 nm, respectively. The UV–Vis–NIR spectrophotometric measurements of transmittance and reflectance elucidated the efficient absorption and light-harvesting of the UV and visible light range with estimated indirect energy gap and Urbach energy ∼1.54 eV and 22.3 meV, respectively. Next, the dispersion behavior of the fabricated thin films is analyzed in the light of the single-oscillator model estimating the detail dispersion parameters. Furthermore, the dielectric function, as well as the nonlinear optical parameters, is accurately estimated. Subsequently, the microelectronic parameters of the engineered rectifying Ag/CBB/p-Si/Al heterojunction such as ideality factor, barrier height, series, and shunt resistances are estimated at different temperatures. The charges dynamical mechanism and the interface states density profile are analyzed, and the thermionic emission model is confirmed to fit the low bias region with a modified Richardson constant of about 34.8A/cm2K2.After that, the photoresponse of the implemented organic/inorganic heterojunction is checked at different illumination intensities and showed a significant stable sensitivity with fast On-Off switching behavior. The fabricated heterojunction achieved good figures of merit such as responsivity, specific detectivity, linear dynamic range, and rise/fall time of about 4.289 mA/W, 2.07 × 109 Jones, 30.36 dB, and 61.6/82.5 ms, respectively. The good and stable responsive performance of the current Ag/CBB/p-Si/Al architecture may make it a potential candidate for photodetection applications.

Visualizing the Orientation of Single Polymers Induced by Spin-Coating.

The orientation of chains within polymeric materials influences their electrical, mechanical, and thermal properties. While many techniques can infer the orientation distribution of a bulk ensemble, it is challenging to determine this information at the single-chain level, particularly in an environment of otherwise identical polymers. Here, we use single-molecule localization microscopy (SMLM) to visualize the directions of chains within spin-coated polymer films. We find a strong relationship between shear force and the degree and direction of orientation, and additionally, we reveal the effects of chain length and solvent evaporation rate. This work utilizes single-chain resolution to observe the important, though often overlooked, property of chain orientation in the common fabrication process of spin-coating.

Influence of 8 MeV Electron Irradiation on the Properties of ZnO Nanocrystalline Thin Films for Optoelectronic Devices in the High Radiation Environment

Herein, we present the influence of 8 MeV electron beam irradiation on the structural, optical and electrical properties of sol-gel derived spin-coated ZnO films. The electron irradiation doses varied from 0 kGy to 10 kGy. We observed significant changes in the morphology, optical and electrical properties of the films upon irradiation. Structural analysis of the films revealed the preferential and dominant c-axis orientation of the crystallites along the (002) plane. The preferential growth of the films was also supported by the values of texture coefficient. Atomic Force Microscopy studies reveal the linear relationship between the surface roughness, grain size and irradiation dose. The average transmittance of the films decreased from 87% to 66% after irradiation. A slight red-shift of the optical band gap values was observed when the absorbed dose was increased from 0 kGy to 10 kGy. The Photoluminescence measurement of the films showed that the intensity of the defect-related peak increases with the electron dose. The electrical resistivity of the films decreased after irradiation and a minimum resistivity of 7.566 × 10−2 Ω m was obtained from the film irradiated with a 5 kGy electron dose. To find the performance and quality of the prepared film, the Figure of Merit was calculated and was found that the film irradiated with a 5 kGy electron dose shows the maximum value. The obtained results show that electron irradiation is a potential alternative approach to improve the performance of the ZnO films for optoelectronic devices in a high radiation environment.

High-Throughput Direct Writing of Metallic Micro- and Nano-Structures by Focused Ga+ Beam Irradiation of Palladium Acetate Films.

Metallic nanopatterns are ubiquitous in applications that exploit the electrical conduction at the nanoscale, including interconnects, electrical nanocontacts, and small gaps between metallic pads. These metallic nanopatterns can be designed to show additional physical properties (optical transparency, plasmonic effects, ferromagnetism, superconductivity, heat evacuation, etc.). For these reasons, an intense search for novel lithography methods using uncomplicated processes represents a key on-going issue in the achievement of metallic nanopatterns with high resolution and high throughput. In this contribution, we introduce a simple methodology for the efficient decomposition of Pd3(OAc)6 spin-coated thin films by means of a focused Ga+ beam, which results in metallic-enriched Pd nanostructures. Remarkably, the usage of a charge dose as low as 30 μC/cm2 is sufficient to fabricate structures with a metallic Pd content above 50% (at.) exhibiting low electrical resistivity (70 μΩ·cm). Binary-collision-approximation simulations provide theoretical support to this experimental finding. Such notable behavior is used to provide three proof-of-concept applications: (i) creation of electrical contacts to nanowires, (ii) fabrication of small (40 nm) gaps between large metallic contact pads, and (iii) fabrication of large-area metallic meshes. The impact across several fields of the direct decomposition of spin-coated organometallic films by focused ion beams is discussed.

Liquid/liquid interfacial cross-linking reaction of conjugated polymer prepared cross-linked films with improved electrochromic and capacitance properties

Interfacial crosslinking is a useful and unique method for preparing films with desired structures. Here, a crosslinked structure film (Rc-mProdot) is obtained from the linear polymer (mProdot) with cross-linkable functional side-chains via the liquid/liquid interfacial crosslinking. Transmission phenomenon and Tyndall effect reflected the assembling progress of Rc-mProdot film. FT-IR and SEM data prove the formation of the desired cross-linked polymer film with loose structure precisely. Significantly, the desirable Rc-mProdot film not only retains the original color and similar electrochemical behaviors to these of the spin-coated mProdot polymer film, but also exhibits improved electrochromic and capacitance properties including a faster electrochromic discoloring time (0.26 s), larger capacitance (increasing by 60% than Rc-mProdot film) and a better charge-discharge stability (retaining 79.1% after 600 cycles). This work provides a simple and efficient approach to liquid/liquid interfacial Schiff-base reaction to construct conjugated polymer films with loose structure towards improving electrochromic and supercapacitor performance and applications.

Band-like transport in non-fullerene acceptor semiconductor Y6

The recently reported non-fullerene acceptor (NFA) Y6 has been extensively investigated for high-performance organic solar cells. However, its charge transport property and physics have not been fully studied. In this work, we acquired a deeper understanding of the charge transport in Y6 by fabricating and characterizing thin-film transistors (TFTs), and found that the electron mobility of Y6 is over 0.3–0.4 cm2/(V⋅s) in top-gate bottom-contact devices, which is at least one order of magnitude higher than that of another well-known NFA ITIC. More importantly, we observed band-like transport in Y6 spin-coated films through temperature-dependent measurements on TFTs. This is particularly amazing since such transport behavior is rarely seen in polycrystalline organic semiconductor films. Further morphology characterization and discussions indicate that the band-like transport originates from the unique molecule packing motif of Y6 and the special phase of the film. As such, this work not only demonstrates the superior charge transport property of Y6, but also suggests the great potential of developing high-mobility n-type organic semiconductors, on the basis of Y6.Graphical

Synthesis and characterisation of triphenylmethine dyes for colour conversion layer of the virtual and augmented reality display

Five triphenylmethine dyes were designed and synthesised for the blue colour conversion layer of virtual and augmented reality displays. To form subpixel patterns suitable for high-brightness microdisplay panels, the prepared dyes must exhibit high solubility, colour strength, durability, and colour purity. For this purpose, three major strategies were introduced: dimerisation of triphenylmethine, chlorination, and counterion exchange. The electrostatic and spectroscopic characteristics of the synthesised dyes were investigated and predicted using computational calculations. The counter anion-modified dyes exhibited superior optical properties and thermal- and photo-stabilities compared to their parent dyes. The modified dyes also showed enhanced solubility toward industrial solvents because of their highly twisted chemical structures and weakly coordinating counter anion substituents. The synthesised dyes were chlorinated to optimise blue colour tuning and prevent the agglomeration of dyes. DTPM-Cl-HFPSI was selected as the main colourant, and EV-HFPSI was selected as the colour-matching colourant to manufacture optimal deep blue colour resists. The optimised spin-coated films exhibited high transmittance in the blue region and excellent properties in terms of brightness and colour purity by absorption over a wide and appropriate visible region.

Structure and mid-infrared optical properties of spin-coated polyethylene films developed for integrated photonics applications

Polyethylene is a promising polymer for mid-infrared integrated optics due to its broad transparency and optimal refractive index. However, simple fabrication protocols that preserve its optical characteristics are needed to foster a wide range of applications and unlock its full potential. This work presents investigations of the optical and structural properties of spin-coated linear low-density polyethylene films fabricated under humidity-controlled conditions. The film thickness on polymer concentration dependence shows a non-linear behavior, in agreement with previously reported theoretical models and allowing predictive concentration-dependent thickness deposition with high repeatability. The surface roughness is on the nanometer-scale for all investigated concentrations between 1% and 10%. The crystallinity of the films was studied with the Raman spectroscopy technique. Mid-infrared ellipsometry measurements show a broad transparency range as expected for bulk material. Layer exposure to solvents revealed good stability of the films, indicating that the fabricated layers can outlast further fabrication steps. These investigations confirm the excellent properties of spin-coated thin films fabricated with our novel method, creating new opportunities for the use in photonic integrated circuits

Effect of Varying Doping Level on Structural, Electrical and Optical Properties of Al Doped ZnO Spin Coated Films

The synthesis and characterization of spin-coated Al-doped ZnO (AZO) thin films with varying Al concentrations (0%, 5%, 10%, 15% and 20%) onto glass substrates have been demonstrated in this paper. The structural, electrical and optical properties of the spin-coated thin films have been investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis, Van Der Pauw method and UV-visible spectroscopy. The EDX study shows well-defined peaks which confirm the presence of only Zn, O and Al and no other impurities in the films. The increase of Al and decrease of Zn weight percentages with increasing doping level confirms the effective substitution of Zn by Al. SEM of the surfaces of the films shows that undoped ZnO films contain particle agglomeration which is reduced with Al doping and the surfaces of the films gradually became more uniform. The thickness of the AZO films varied from 86 to 699 nm with increasing Al doping concentration. The electrical conductivity of the films increased up to ~ 7 × 10-2 (Ω.cm)-1 due to doping with 5% Al concentration. The optical transmittance highly increased above 95% in the visible range with the introduction of Al dopant and it kept rising with the increase of Al concentration. The optical energy band gap of undoped ZnO increased from 3.275eV to 3.342 eV with 5% Al doping.

Structural and Optical Studies on Sol-Gel Driven Spin-Coated CdS Thin Films

Inorganic wide band gap semiconductors are considered as best for optoelectronic devices such as photovoltaic cells, photodetectors, thin film transistors etc. CdS is a more promising semiconductor due to its direct wide band-gap ∼ 2.42 eV and size dependent optical properties. In the present article, structural and optical properties of spin coated CdS thin films are investigated. CdS thin films are annealed at 400 °C for 60 minutes to improve crystalline quality. X-RAY diffraction pattern reveals (002) diffraction plane of wurtzite CdS. The optical properties are analyzed by UV-Visible-NIR spectroscopy. The optical band-gap of CdS thin films varies from 2.25 eV to 2.47 eV which depends on number of deposited layers and the annealing condition.

Prospect of SnO2 Electron Transport Layer Deposited by Ultrasonic Spraying

The SnO2 electron transport layer (ETL) has been characterized as being excellent in optical and electrical properties, ensuring its indispensable role in perovskite solar cells (PSCs). In this work, SnO2 films were prepared using two approaches, namely, the ultrasonic spraying method and the traditional spin-coating, where the different properties in optical and electrical performance of SnO2 films from two methods were analyzed by UV–Vis, XRD, AFM, and XPS. Results indicate that the optical band gaps of the sprayed and the spin-coated film are 3.83 eV and 3.77 eV, respectively. The sprayed SnO2 film has relatively low surface roughness according to the AFM. XPS spectra show that the sprayed SnO2 film has a higher proportion of Sn2+ and thus corresponds to higher carrier concentration than spin-coated one. Hall effect measurement demonstrates that the carrier concentration of the sprayed film is 1.0 × 1014 cm−3, which is slightly higher than that of the spin-coated film. In addition, the best PCSs efficiencies prepared by sprayed and spin-coated SnO2 films are 18.3% and 17.5%, respectively. This work suggests that the ultrasonic spraying method has greater development potential in the field of flexible perovskite cells due to its feasibility of large-area deposition.

Correction to Air-Exposure Induced Dopant Redistribution and Energy Level Shifts in Spin-Coated Spiro-MeOTAD Films

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Air-Exposure Induced Dopant Redistribution and Energy Level Shifts in Spin-Coated Spiro-MeOTAD FilmsZafer HawashZafer HawashMore by Zafer Hawash, Luis K. OnoLuis K. OnoMore by Luis K. Onohttps://orcid.org/0000-0003-3176-1876, Sonia R. RagaSonia R. RagaMore by Sonia R. Raga, Michael V. LeeMichael V. LeeMore by Michael V. Lee, and Yabing Qi*Yabing QiMore by Yabing Qihttps://orcid.org/0000-0002-4876-8049Cite this: Chem. Mater. 2022, 34, 8, 3882Publication Date (Web):April 7, 2022Publication History Published online7 April 2022Published inissue 26 April 2022https://doi.org/10.1021/acs.chemmater.2c00951Copyright © 2022 American Chemical SocietyRIGHTS & PERMISSIONSACS AuthorChoiceArticle Views470Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (553 KB) Get e-Alerts Get e-Alerts