Fluorinated Polymer Layer Research Articles

Interfacial fluorinated polymer layer enabling highly stable, fast response, high-performance self-powered PEA2PbBr4 ultraviolet photodetector

A fast-response, self-powered UV photodetector is highly desirable in health and safety applications to monitor UV exposure, especially to the human body. PEDOT: PSS is known as an effective hole transport layer often used in the fabrication of organic electronics. However, the moisture-sensitive PEDOT: PSS resulted in poor surface coverage and degradation of perovskite material, leading to lower performance and instability of the device. In this work, adding hydrophobic Nafion layer on top of PEDOT: PSS and perovskite interface dramatically increased the photocurrent and stability. The best device based on PEA2PbBr4 films with a Nafion layer exhibited a high photocurrent of 0.34 mA/cm2 and a fast response speed of 15.6 μs at 0 V bias. The responsivity and detectivity of the optimized device were calculated to be 25 mA/W and 2.54 × 1011 Jones, respectively. The improved device performance is a direct result of the enhanced surface coverage as shown by field-emission scanning electron microscope and energy dispersive x-ray spectroscopy. Furthermore, the PEA2PbBr4 films and devices based on Nafion coated PEDOT: PSS showed a better UV light stability than those without the Nafion layer due tothe hydrophobic nature of the Nafion layer. As a result of this simple technique, high-performance PEA2PbBr4 photodetector can be fabricated.

Fluoropolymer-based organic memristor with multifunctionality for flexible neural network system

In this study, we propose an effective strategy for achieving the flexible one organic transistor–one organic memristor (1T–1R) synapse using the multifunctional organic memristor. The dynamics of the conductive nanofilament (CF) in a hydrophobic fluoropolymer medium is explored and a hydrophobic fluoropolymer-based organic memristor is developed. The flexible 1T–1R synapse can be fabricated using the solution process because the hydrophobic fluorinated polymer layer is produced on the organic transistor without degradation of the underlying semiconductor. The developed flexible synapse exhibits multilevel conductance with high reliability and stability because of the fluoropolymer film, which acts as a medium for CF growth and an encapsulating layer for the organic transistor. Moreover, the synapse cell shows potential for high-density memory systems and practical neural networks. This effective concept for developing practical flexible neural networks would be a basic platform to realize the smart wearable electronics.

Facile fabrication of ultraviolet light cured fluorinated polymer layer for smart superhydrophobic surface with excellent durability and flame retardancy

Functional superhydrophobic coatings have raised wide concern due to their promising application in superhydrophobic paints, packaging materials, building materials etc, which call for the requirements of mechanical stability and flame retardancy. Herein, a series of UV cured superhydrophobic PVDT coatings with mechanical stability and flame retardancy were prepared using an all-in-one suspension containing trimethylolpropane triacrylate (TMPTA), vinyltriethoxysilane (VTES), 1H, 1H, 2H, 2H-Perfluorododecanethiol (PFDT), 9,10-Dihydro-9-Oxa-10-Phosphaphenanthrene-10-Oxide (DOPO), nano-SiO2 particles, and 2-Hydroxy-2-methylpropiophenone (HMPP). The reaction mechanism, surface morphology, phase composition of the PVDT coatings were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The PVDT coatings exhibited excellent low adhesion against water droplets, superhydrophobicity and self-cleaning property when the content of nano-SiO2 reached to 40 wt%. Good mechanical and chemical stability of PVDT coatings was confirmed by abrasion test, tape adhesion test and corrosive media treatment. Further, the combustion experiments indicated that the PVDT coatings exhibited excellent flame retardancy and significant ignition delay. All these results demonstrated that the prepared PVDT coatings tended to achieve wide application in waterproof and fireproof materials.

Engineering the mechanical properties of ultrabarrier films grown by atomic layer deposition for the encapsulation of printed electronics

Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion mismatch, elastic constant mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al2O3)/hafnium oxide (HfO2) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50 °C/85% relative humidity. Inserting a SiNx layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

Effect of plasma fluorination variables on the deposition and growth of partially fluorinated polymer over PMMA films

In this work, an investigation was made of the modification of film surface of Poly(methylmethacrylate) (PMMA) using the plasma polymerization technique. PMMA films 10 µm thick were obtained by Spin-Coating starting from a chloroform solution (15.36% w/w). The films were exposed to the plasma of CHF3 at different gas pressures and exposure times to increase the thickness of fluorinated polymers onto PMMA films. The plasma fluorinated optical films were characterized by gravimetry, FTIR-ATR, contact angle of wetting, SEM and AFM. The surface fluorination of PMMA films can be inferred by the increase in contact angle under all experimental conditions, and confirmed with FTIR-ATR analysis. Gravimetry showed an increase of the fluorinated polymer layer over PMMA films, being 1.55 µm thick at 0.7 torr and 40 minutes of plasma exposure. The SEM analysis showed a well-defined layer of fluorinated polymer, with fluorine being detected in the EDS analysis. The film roughness for the fluorinated polymers was around of 200 A, quite satisfactory for a 1.55 µm cladding.

Evaluation of the deformation strength properties of a fluorinated polymer layer on the surface of poly(ethylene terephthalate) films

Evaluation of the deformation strength properties of a fluorinated polymer layer on the surface of poly(ethylene terephthalate) films

Fabrication of flexible UV nanoimprint mold with fluorinated polymer-coated PET film

UV curing nanoimprint lithography is one of the most promising techniques for the fabrication of micro- to nano-sized patterns on various substrates with high throughput and a low production cost. The UV nanoimprint process requires a transparent template with micro- to nano-sized surface protrusions, having a low surface energy and good flexibility. Therefore, the development of low-cost, transparent, and flexible templates is essential. In this study, a flexible polyethylene terephthalate (PET) film coated with a fluorinated polymer material was used as an imprinting mold. Micro- and nano-sized surface protrusion patterns were formed on the fluorinated polymer layer by the hot embossing process from a Si master template. Then, the replicated pattern of the fluorinated polymer, coated on the flexible PET film, was used as a template for the UV nanoimprint process without any anti-stiction coating process. In this way, the micro- to nano-sized patterns of the original master Si template were replicated on various substrates, including a flat Si substrate and curved acryl substrate, with high fidelity using UV nanoimprint lithography.

Origin of the efficiency enhancement in ferroelectric functionalized organic solar cells

We have investigated the efficiency enhancement of organic solar cells upon incorporation of a thin ferroelectric polymer layer. For non-Ohmic contacts the enhancement is due to an increased open circuit voltage, which is, however, independent of the ferroelectric polarization direction. Ferroelectricity cannot play a role due to depolarization and charge compensation. The same improvement is also obtained with a non-ferroelectric fluorinated polymer. The data unambiguously show that the improved efficiency is solely due to improvement of the cathode. The fluorinated polymer layer plays the role of LiF in an optimized solar cell.

Pretilt study of double‐layer alignment film (DLAF)

A novel double‐layer alignment film (DLAF) was developed to obtain greater control of the alignment characteristics of the liquid crystal director. The DLAF consists of a thin fluorinated polymer layer on the top of a rubbed non‐fluorinated, non‐branched polyimide layer (PI 2555). Two types of fluorinated polymer with different chemical structures and wetting behaviour on PI 2555 were chosen, to provide either continuous or discontinuous top layers. The continuous top layer DLAF (DLAF‐1) exhibits an abrupt pretilt transition from planar to homeotropic as the top layer thickness increases. The discontinuous top layer DLAF (DLAF‐2) exhibits a gradual transition where the pretilt correlates with the coverage of fluorinated top layer. These two types of transitions fit with de Gennes' local Frederick's transition and Kwok's inhomogeneous alignment theories, respectively. The abrupt pretilt transition system may be promising for chemical/biosensor applications, whereas the gradual transition system is suitable for pretilt control in LCD devices.

Pulsed Excimer Laser Photoablation by Backside Irradiation of Thin Metal Coated Polymer Films

AbstractBackside laser irradiation of metal coated quartz wafers can be used for transferring material imagewise to a target cleanly in absence of chemical vapors. However, the transfer of metal from a quartz surface requires a high energy, resulting in poor quality images in some cases.Use of a fluorinated polymer layer between the polycarbonate substrate and a Te-Se metal alloy is known for clean fabrication of metal holes in write-once-read-only memory media. Polymer thin films can be used similarly in backside laser irradiation for metal ejection from substrate surfaces.With an ArF excimer laser at 193 nm, gold and aluminum were ejected imagewise from Teflon AF, poly(methacrylonitrile) and quartz surfaces. The threshold fluences of 230 Å thick gold films from polymer surfaces were 7.9 to 9.7 mJ/cm2, whereas the threshold fluence from a quartz surface was determined to be 17.8 mJ/cm2. For aluminum on top of quartz and aluminum coated polymers, higher threshold fluences were found compared to gold ranging from 12.96 to 22.7 mJ/cm2.Also, interfacial reactions between the polymer films and the metal layer occured and have been studied by SEM and XPS.

Surface fluorination of poly(1-(trimethylsilyl)-1-propyne) in carbon tetrafluoride plasma for gas separation membranes.

Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) has been treated with a glow discharge plasma containing CF4, CF4/H2 or Ar and the chemical composition and structure of plasma-treated surface layer of PTMSP were examined with Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) studies. Gas permeation behavior of plasma-treated PTMSP were also reported. The series resistance model was used to estimate the transport properties of the fluorinated polymer layer. The fact that plasma fluorination of PTMSP leads to a reduction in permeation rate of O2 and N2 accompanied by a significant increase in selectivity of O2 to N2 is especially interesting from a standpoint of membrane separation,

Surface fluorination of composite membranes. Part I. Transport properties

The potential utility of surface fluorination for improving the gas separation properties of a polymer membrane was investigated using poly (4-methyl-1-pentene). It was found that fluorination leads to a reduction in flux accompanied by a very significant increase in selectivity and that after this initial change these trends continue to a lesser degree for up to one year after fluorination. An idealized composite structure consisting of a fluorinated layer with unfluorinated material comprising the rest of the thickness is used to visualize the structure of these membranes. The series resistance model is used to illustrate the relationship between the total membrane thickness and the fraction that the fluorinated polymer layer contributes to the total. This relationship was demonstrated experimentally by fluorinating composite membranes with a permselective poly (4-methyl-1-pentene) layer ranging in thickness from 0.2 to 20 μm. The transport of six gases was measured. The series resistance model was used to estimate the transport properties of the fluorinated polymer layer.