ITO-coated Polyethylene Terephthalate Substrates Research Articles

Niobium Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

Niobium oxide thin films were grown on both rigid and flexible substrates using DC magnetron sputtering for electrochromic applications. Three experimental series were conducted, varying the oxygen to argon flow rate ratio and deposition time. In the first series, the oxygen to argon ratio was adjusted from 0 to 0.32 while maintaining a constant growth time of 30 min. For the second and third series, the oxygen to argon ratios were fixed at 0.40 and 0.56, respectively, with deposition times ranging from 15 to 60 min. A structural transition from crystalline to amorphous was observed at an oxygen to argon flow rate ratio of 0.32. This transition coincided with a change in appearance, from non-transparent with metallic-like electrical conductivity to transparent with dielectric behavior. The transparent niobium oxide films exhibited thicknesses between 51 nm and 198 nm, with a compact, dense, and featureless morphology, as evidenced by both top-view and cross-sectional images. Films deposited on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates displayed a maximum surface roughness (Sq) of 9 nm and a maximum optical transmission of 83% in the visible range. The electrochromic response of niobium oxide thin films on ITO-coated PET substrates demonstrated a maximum coloration efficiency of 30 cm2 C−1 and a reversibility of 96%. Mechanical performance was assessed through bending tests. The ITO-coated PET substrate exhibited a critical bending radius of 6.5 mm. Upon the addition of the niobium oxide layer, this decreased to 5 mm. Electrical resistance measurements indicated that the niobium oxide film mitigated rapid mechanical degradation of the underlying ITO electrode beyond the critical bending radius.

Composite design of two-dimensional inorganic nanosheets for flexible energy storage capacitors

We present a new approach for designing flexible energy storage capacitors using two-dimensional (2D) inorganic nanosheets. 2D dielectric Ca2Nb3O10 nanosheet and ferroelectric poly(vinylidene fluoride) (PVDF) were selected as model material systems. Langmuir–Blodgett deposition was utilized for layer-by-layer engineering of (Ca2Nb3O10/PVDF) nanocomposite films on an indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrate. Such a new composite design realized the simultaneous improvement of energy density (∼7 J cm−3) and efficiency (∼78 %) even in the ultrathin form (∼20 nm) on the ITO-coated PET substrate. Nanosheet-based flexible capacitors also maintained a stable performance even after 104 times bending cycles. These results indicate that our nanosheet approach is of technological importance for exploring new flexible dielectric capacitors.

Fabrication of graphene\u2013ZnO heterostructure-based flexible and thin platform-based UV detector

This work presents the performance evaluation of Graphene/ZnO Schottky junctions grown on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates. The fabricated structures include chemical vapour deposition grown graphene layer on ITO-coated PET substrates. Polymethyl methacrylate assisted transfer method has been employed for the successful transfer of graphene from Cu substrate to PET. The smaller D-band intensity (1350 cm−1) compared to G-band (1580 cm−1) indicates good quality of carbon lattice with less number of defects. High-quality ZnO has been deposited through RF sputtering. The deposited ZnO with grain size 50–95 nm exhibited dislocation densities of 1.31270 × 10–3 nm−2 and compressive nature with negative strain of − 1.43156 GPa. Further, the electrical and optical characterization of the devices has been done through device I–V characterization and UV detection analysis. The UV detection capability of the device has been carried out with the aid of a UV-lamp of 365 nm wavelength. The fabricated graphene/ZnO photodetector showed good response to UV illumination. The device performance analysis has been done through a comparison of the device responsivity and detectivity with the existing detectors. The detectivity and responsivity of the fabricated detectors were 7.106 × 109 mHz1/2 W−1 and 0.49 A W−1, respectively.

Correction to: Structural and optical analysis of Ag nanoparticle-assisted and vertically aligned TiO2 nanowires for potential DSSCs application

In this work, vertically aligned TiO2 nanowires (TiO2-NWs) and Ag nanoparticle (Ag-NP)-assisted and vertically aligned TiO2 nanowires (TAT-NWs) were deposited on glass and flexible polyethylene terephthalate (PET) substrates using the glancing angle deposition (GLAD) technique. The morphology and structural analysis of the samples manifest successful deposition of vertically aligned TiO2-NWs and TAT-NWs. The high-resolution transmission electron microscopy (HR-TEM) image of TiO2-NWs shows the polycrystalline nature. Further, the X-ray diffraction (XRD) result confirms the polycrystalline nature of both the TiO2-NW and TAT-NW samples. Besides, HR-TEM image confirms the presence of small crystal grains of Ag-NPs at the mid of the annealed TAT-NWs. It is evident from the selected area electron diffraction (SAED) analysis of TiO2-NWs and annealed TAT-NWs that the crystallinity of TiO2 present in the annealed TAT-NWs improves after annealing. The absorption spectrum analysis of TAT-NWs deposited on glass substrate shows enhances absorption peak in the visible region with a maximum peak at ~ 450 nm wavelength compared to the TiO2-NWs, which may be attributed to the surface plasmon resonance (SPR) effect of Ag-NPs. Further, it is interesting to observe that the TAT-NWs deposited on PET substrate show further absorption enhancement in the UV and visible regions. In addition, the photoluminescence (PL) analysis reveals that the band gap of TiO2-NWs is ~ 3.12 eV. Therefore, the proposed method of fabricating TAT-NWs on glass and flexible ITO-coated PET substrates using the GLAD technique may be applicable for developing novel photoanode for dye-sensitized solar cells (DSSCs) and other optoelectronic applications.

Experimental analysis of interfacial shear stress and electrical resistance of indium tin oxide-coated polyethylene terephthalate films for a whole folding test

The purpose of this study is to analyze the performance of the flexible conductive substrate by interfacial shear stress. This study performed automatic liquid-crystal modulating common-path interferometry (LMCI) optical inspections on 125-µm polyethylene terephthalate (PET) substrates having indium tin oxide (ITO) coating thicknesses of 80 nm, 160 nm, and 230 nm. The nonlinear characteristic of the stress-optical coefficient of the ITO material is obtained using LMCI. To validate the performance of the flexible conductive substrate, this study has utilized an automatic sliding-folding testing platform (ASTP) for a whole-folding test. Eventually, this study successfully has utilized interface shear stresses to validate the performance of the flexible conductive substrate depended on the different thicknesses of the conductive layers for whole-folding test by using LMCI and ASTP. According to the measurement results, as the folding radii decrease and the ITO thicknesses of ITO-coated PET substrates increase, the changes of interfacial shear stresses increase in compressive direction and the change-rates of electrical resistance of ITO-coated PET substrate also increase. Therefore, the interfacial shear stress measurement and analysis results depicted on flexible conductive substrates provide a validation for improving the manufacturing process and for reducing process residual stresses.

Experimental and Simulated Investigations of Thin Polymer Substrates with an Indium Tin Oxide Coating under Fatigue Bending Loadings.

Stress-induced failure is a critical concern that influences the mechanical reliability of an indium tin oxide (ITO) film deposited on a transparently flexible polyethylene terephthalate (PET) substrate. In this study, a cycling bending mechanism was proposed and used to experimentally investigate the influences of compressive and tensile stresses on the mechanical stability of an ITO film deposited on PET substrates. The sheet resistance of the ITO film, optical transmittance of the ITO-coated PET substrates, and failure scheme within the ITO film were measured to evaluate the mechanical stability of the concerned thin films. The results indicated that compressive and tensile stresses generated distinct failure schemes within an ITO film and both led to increased sheet resistance and optical transmittance. In addition, tensile stress increased the sheet resistance of an ITO film more easily than compressive stress did. However, the influences of both compressive and tensile stress on increased optical transmittance were demonstrated to be highly similar. Increasing the thickness of a PET substrate resulted in increased sheet resistance and optical transmittance regardless of the presence of compressive or tensile stress. Moreover, J-Integral, a method based on strain energy, was used to estimate the interfacial adhesion strength of the ITO-PET film through the simulation approach enabled by a finite element analysis.

Ionic Liquid-Assisted Electropolymerization for Lithographical Perfluorocarbon Deposition and Hydrophobic Patterning

We developed a novel approach for hydrophobic patterning: combining the photolithography technique with ionic-liquid (IL)-based electropolymerization to fabricate a hydrophobic pattern. Perfluoro-functionalized 3,4-ethylenedioxythiophene (EDOT-F) dispersed in ILs was directly electropolymerized on substrates, which were patterned in advance with positive photoresists. The positive photoresists did not dissolve in ionic liquids during the electropolymerization process, and the poly(EDOT-F) film created hydrophobic domains, which resulted in hydrophobic patterning. This approach provides desired patterns with a lateral resolution consistent with the mask for photolithography. Two kinds of modified indium-tin-oxide-coated glass (ITO-glass) substrates were used to demonstrate the feasibility of process for creating a hydrophobic pattern: ITO-glass substrates coated with nanostructured PEDOT, and the same substrates coated with Au nanoparticles. By confining water droplets on these two patterned substrates to form droplet arrays, we demonstrated two potential applications: multiple droplet-type electrochemical cells and surface-enhanced Raman scattering platforms. In addition, we also applied this approach to create hydrophobic patterning on ITO-coated polyethylene terephthalate (ITO-PET) substrates. The droplet arrays remained well-organized on the ITO-PET substrates even when the substrates were bent. Our work successfully introduced ILs into the photolithography process, implying great potential for these green solvents.

Solution-processed transparent conducting electrodes with graphene, silver nanowires and PEDOT:PSS as alternative to ITO

Novel transparent electrodes, including graphene, silver nanowires (AgNWs) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) serving as the low-cost and flexible alternative to indium tin oxide (ITO) are of interest to the organic electronic industry in recent years. In this paper, transparent, flexible and conductive nanocomposite electrodes were fabricated by using different combinations of graphene, AgNWs, PEDOT:PSS materials via spin coating technique. Optical, morphological and electrical properties of solution-processed electrodes were characterized. Transparent conductive electrode (TCE) based on PEDOT:PSS/AgNW/graphene construction exhibited 216.67 Ω/sq sheet resistance with ~ 83% transparency. Additionally, after 100 cycles of bending, the sheet resistance of PEDOT:PSS/AgNW/graphene electrode on the flexible polyethylene terephthalate (PET) substrate was found to be about 223 Ω/sq, while conventional ITO-coated PET substrate exhibited 83,050 Ω/sq resistance, which was about 400 times more than that of resistance before bending. Optical and electrical measurements showed that obtained nanocomposite electrodes may be promising alternatives to ITO to be used in flexible optoelectronic devices.

Residual and Induced Birefringence Measurement of ITO-Coated PET Substrate by Photoelastic Method

Indium tin oxide (ITO) coated polyethylene terephthalate (PET) is widely used as the substrate for the flexible electronics and photonic devices and displays. These PET substrates are found to be birefringent due to the residual stress induced during manufacturing process, which may change the optical properties of display devices. In this paper, we report the measurement of the residual and induced birefringence as a function of the bending applied to the PET substrates for red, green, and blue (RGB) wavelengths of laser light. We have used the basic photo elasticity set-up for recording the interference fringes using CCD camera. The recorded interferograms were analyzed from the line profile calculated by the MATLAB program. We found that the change in birefringence for ITO/PET substrate follow the Cauchy's law of dispersion for the different applied curvature, for the RGB wavelengths.

Flexible organic ferroelectric films with a large piezoelectric response

Compared with ferroelectric oxides, organic ferroelectric materials are lightweight, flexible and easy to process. They are ideal for applications in the next-generation portable electronics. Here, we demonstrate the room-temperature growth of imidazolium perchlorate (C3N2H5ClO4) ferroelectric films on various substrates, including Pt-coated Si, quartz and, more importantly, on flexible and transparent polyethylene terephthalate (PET). The films have a preferred (0 −1 −1) or (1 0 −1) orientation. The former shows a piezoelectric response comparable with the response of the Pb(Zr0.2Ti0.8)O3 film. This is attributed to the smaller elastic constant of the film, which makes it less susceptible to substrate clamping. When grown on PET, the film is transparent and can be bent to radii of a few millimetres without affecting its ferroelectric properties. Our discovery may significantly promote the application of molecular ferroelectrics in flexible and transparent electronics. Flexible organic ferroelectric films exhibiting a high piezoelectric response have been fabricated by researchers in China and Singapore. Organic ferroelectric materials possess many advantages over ferroelectric oxides, including being lightweight, flexible and easy to process as well as usually being transparent. These properties make them ideal for use in flexible and portable electronic devices, but this requires growing thin films of them on substrates. Now, Guoliang Yuan and co-workers have achieved room-temperature growth of high-quality thin films of the ferroelectric imidazolium perchlorate (C3N2H5ClO4) on various substrates. Importantly, they succeeded in growing thin films on polyethylene terephthalate (PET) substrates and show that the system can be bent to radii of a few millimetres without affecting its ferroelectric properties. This demonstration raises the possibility of using molecular ferroelectrics in flexible and transparent electronics. The transparent C3N2H5ClO4 ferroelectric film on ITO coated PET substrate can be bent to 3.1 mm radius without affecting its ferroelectric properties. Furthermore, its local piezoelectric response is comparable to that of Pb(Zr0.2Ti0.8)O3 film.

Highly Conductive DMSO-Treated PEDOT:PSS Electrodes Applied to Flexible Organic Solar Cells

Highly conductive poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT : PSS) attracts a strong attention as a transparent electrode material since it may replace indium tin oxide (ITO) electrodes used in many organic semiconductor devices. However, PEDOT : PSS films have been usually deposited using acidic precursors, which caused long term device degradation as well as safety issues during device fabrication processes. This paper firstly reports application of highly conductive PEDOT : PSS films deposited on polyethylene terephthalate (PET) substrates using a neutralized precursor to organic bulkhetrojunction solar cells. The sheet resistance (Rs) of PEDOT : PSS was reduced by more than two orders of magnitudes by spin coating the neutralized solution containing 5% of dimethyl sulfoxide (DMSO) and dipping the films in DMSO for 30min. Subsequently, an approximately 55 nm-thick PEDOT : PSS layer was obtained with Rs =159 Ω/□, a conductivity of 1143 S/m, and an optical transmittance of 84%. A solar cell based on poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene2, 6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3, 4-b]thiophenediyl]: [6,6]-phenyl-C71-butyric acid methyl ester fabricated on the PEDOT: PSS/PET substrate exhibited a higher open circuit voltage and power conversion efficiency than did a control solar cell fabricated on an ITOcoated PET substrate. These results suggest that the highly conductive PEDOT : PSS films may contribute to realize ITO-free flexible organic solar cells. key words: PEDOT:PSS, DMSO, Organic solar cells

Investigation on residual stress and stress-optical coefficient for flexible electronics by photoelasticity

For flexible electronics in manufacture, the full-field stress measurement is an important issue for the film deposited on the flexible substrate. In this work, the two-dimensional photoelasticity is proposed to measure stress-optical coefficients and an analytical derivation is carried out for investigation on full-field residual stresses under tensional forces. In experimental setup, a polarization beam splitter (PBS) is used to connect with two CCD cameras that are used to capture the intensity of right-hand and left-hand circular polarization separately. It has higher measured speed and better uniformity than a direct rotation method. Stress-optical coefficients can be calculated by extracting the slope from tensional stress versus optical retardation curve. Experimental results show that optical retardations for indium-tin-oxide (ITO)-coated PET (polyethylene terephthalate) substrates can be affected more easily than PET substrates under tensional forces. The difference of stress-optical coefficients between 0° and 90° orientations for PEN (polyethylene naphthalate) substrates is smaller than that for PET substrates. Furthermore, it shows residual stresses for ITO-coated PET substrates in 0° and 90° orientations are different under tensional stress.

Flexible organic light-emitting device based on magnetron sputtered indium-tin-oxide on plastic substrate

A radio-frequency sputtering deposition method was applied to prepare indium tin oxide (ITO) on a plastic substrate, polyethylene terephthalate (PET). The correlation of deposition conditions and ITO film properties was systematically investigated and characterized. The optimal ITO films had a transmittance of over 90% in the visible range (400–700 nm) and a resistivity of 5.0×10 −4 Ω-cm. Sequentially α-napthylphenylbiphenyl diamine, tris-(8-hydroxyquinoline) aluminium, and magnesium–silver were thermally deposited on the ITO-coated PET substrate to fabricate flexible organic light-emitting diodes (FOLEDs). The fabricated devices had a maximum current efficiency of ∼4.1 cd/A and a luminance of nearly 4100 cd/m 2 at 100 mA/cm 2. These values showed that the FOLEDs had comparable performance characteristics with the conventional organic light-emitting diodes made on ITO-coated glasses with the same device configuration.