ITO-coated PET Substrate Research Articles

The impact of series ([formula omitted]) and shunt resistances ([formula omitted]) on solar cell parameters to enhance the photovoltaic performance of f-PSCs

Flexible Perovskite Solar Cells (f-PSCs) are made on an ITO-coated PET substrate. SnO2 has been used as a transparent inorganic electron transporting layer (ETL), PEDOT: PSS as an organic hole transporting layer (HTL), and C H3 N H3 Pb I3 as a perovskite absorbing layer. Two configurations of the device structure have been formed, one is normal structure ITO/PET/ SnO2/C H3 N H3 Pb I3/PEDOT: PSS/Ag (n-i-p) and the other is inverted structure ITO/PET/PEDOT: PSS/C H3 N H3 Pb I3/ SnO2/Ag (p-i-n). An antisolvent (i.e. ethyl acetate) has been used to control the surface morphology of the perovskite layers during fabrication of f-PSCs. Applying antisolvent in perovskite improves carrier mobility, transport properties, and higher power conversion efficiency (PCE) achieved. This study focuses on the effects of series (Rs) and shunt resistance (Rsh) of f-PSCs on photovoltaic parameters while controlling the surface morphology of perovskite films applied on both structures. The study examines the behaviour of f-PSCs with and without the use of an antisolvent. For normal structure, PCE is found at 11.34 % for f-PSCs with antisolvent and 7.96 % for f-PSCs without antisolvent. On the other hand, inverted structures show PCE 10.36 % and 7.46 % for f-PSCs with and without antisolvent, respectively. PCE has been calculated for the f-PSCs by bending the samples about 3 0o angle and about 20 % decrease in PCE has been found. The oddity of this work is to estimate the series and shunt resistant for f-PSCs and find the cost-effective control of these parameters by controlling interfacial defects.

Polymeric Nanofibriller Matrix on ITO Substrate for Flexible Chemical Sensing Applications

The authors present here a facile electrochemical approach to synthesize Poly(Aniline) nanofibriller matrix on ITO coated PET substrate for development of wearable or embeddable sensors. Electrochemical parameters were optimized for even diametric synthesis and controlled length of Poly (Aniline)) nanofibers. A three – step chrono potentiometric deposition was found to be efficient for the synthesis of the matrix. Precise tuning of galvanic conditions during the synthesis process was highly effective and repetitive towards controlling the nucleation of Poly (Aniline) seeds on the substrate that serves as the basis of nanofibers with presumable diameter range. Charge conduction behaviour of the matrix was studied via Linear Sweep Voltammetry and a semiconducting nature was observed. The synthesized nanofibrillar sensor platforms were subjected to Scanning Electron Microscopy (SEM), UV-VIS Spectroscopy and FTIR spectroscopy for elucidation of morphological and structural aspects. The distribution of nanofibers network throughout the substrate was uniform and dendritic. Flexibility characteristics of the sensors were studied by bending the sensor to different radii and in-situ monitoring of resistance. The synthesized sensor platforms were subjected to NO2 sensing in chemiresistive mode under dynamic conditions to investigate the applicability of the same under real-time applications. Upon exposure to different concentrations of NO2, the devices exhibit a rapid response at concentrations as low as 1 ppm. The betterment in overall sensing behaviour in comparison to conventional thin film type sensors could be attributed to the one-dimensional structure of nanofibers leading to effective diffusion on analyte molecules and low scattering loss during charge transport. These flexible sensors can be interesting for novel mobile applications.

Studies on PVDF/ferrite composite films on flexible substrates for pyroelectric energy conversion

Multiferroic flexible composite films on ITO-coated PET substrates for pyroelectric energy conversion. A maximum figure of merit of 8.67% was observed in 5 wt% of MnFe2O4 and 12.19% in 10 wt% of NiFe2O4 composite film.

Demonstration of an Integrated Inorganic–Organic IoT-Enabled System With PV and Electrochromic Devices for Autonomous Smart Windows

Smart windows may incorporate integrated stacks of photovoltaic and electrochromic devices, whose opacity/transparency can be synergistically modulated (and/or wirelessly controlled) by autonomously generated voltages. This article demonstrates a proof of concept of an Internet of Things (IoT)-enabled system comprised of an integrated bulk (organic) heterojunction photovoltaic device with an (inorganic) electrochromic device. First, fully organic (poly[N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2 -thienyl-2’,1’,3’-benzothiadiazole)]:phenyl-C71-butyric-acid-methyl) photovoltaic devices were fabricated, and their performance were evaluated with respect to optical transparency and power conversion efficiency (PCE). Upon varying the hole transport layers and substrates, the strongest performing devices exhibited a PCE of 3.2%, an open-circuit voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V_{\text{oc}}$</tex-math></inline-formula> ) of 0.9 V, and a short-circuit current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$J_{\text{sc}}$</tex-math></inline-formula> ) of 10–15 mA/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{^{2}}$</tex-math></inline-formula> . Second, tungsten trioxide WO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula> electrochromic films were inkjet printed on conductive and transparent ITO-coated PET substrates of varying mechanical flexibility, including PDMS with a network of embedded Ag nanowires and indium- tin-oxide-coated polyethylene terephthalate. The printed electrochromic devices demonstrated clear switching behavior under external bias, with a coloration time of 8 s, a bleaching time of 12 s, and an optical modulation of 0.5874 at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> = 525 nm. Finally, the photovoltaic and electrochromic devices were connected, with a network configuration of the former to provide requisite autonomous power for the demonstration of opacity modulation (or light transmission properties) of the latter, utilizing a Particle IoT controller that was switched wirelessly with a smartphone.

Embedded Oxidized Ag-Pd-Cu Ultrathin Metal Alloy Film Prepared at Low Temperature with Excellent Electronic, Optical, and Mechanical Properties.

Most transparent conducting materials are based on Sn:In2O3 (ITO). When applied onto flexible substrates, ITO can be prepared in an oxide–metal–oxide (OMO) configuration, typically ITO/Ag/ITO, where the ductility of the embedded metal layer is intended to reduce the mechanical brittleness and improve the electrical conductivity of the OMO multilayer. Hitherto, the lower limit of the thickness of the Ag layer has been limited by the percolation threshold, which limits the Ag layer to be thicker than ∼10 nm to avoid agglomeration and to ensure conductivity and structural stability. Metal layers of thicknesses below 10 nm are, however, desirable for obtaining OMO coatings with better optical properties. It is known that agglomeration of the metal layer can, to some extent, be suppressed when substituting Ag by an Ag–Pd–Cu (APC) alloy. APC-based OMO films exhibit excellent optical and electrical properties, but still continuous APC films well below 10 nm thickness cannot be achieved. In this work we demonstrate that controlled oxidation of APC results in smooth, ultrathin APC:O continuous coatings (of thickness ∼5 nm) on ITO-coated PET substrates. Moderate oxidation yields superficial PdOx formation, which suppresses Ag agglomeration, while still maintaining excellent conductivity. On the other hand, extensive oxidation of APC leads to extensive Pd oxide nucleation deteriorating the conductivity of the film. The ITO/APC:O/ITO films exhibit low resistivity, attributed to a high Hall mobility associated with suppressed agglomeration, good stability in high humidity/temperature environments, superior transmittance in the visible and infrared region, and excellent mechanical bending properties, thus providing new opportunities for fabricating superior transparent conducting coatings on polymer substrates.

Soft-Microstructured Transparent Electrodes for Photonic-Enhanced Flexible Solar Cells

Microstructured transparent conductive oxides (TCOs) have shown great potential as photonic electrodes in photovoltaic (PV) applications, providing both optical and electrical improvements in the solar cells’ performance due to: (1) strong light trapping effects that enhance broadband light absorption in PV material and (2) the reduced sheet resistance of the front illuminated contact. This work developed a method for the fabrication and optimization of wavelength-sized indium zinc oxide (IZO) microstructures, which were soft-patterned on flexible indium tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) substrates via a simple, low-cost, versatile, and highly scalable colloidal lithography process. Using this method, the ITO-coated PET substrates patterned with IZO micro-meshes provided improved transparent electrodes endowed with strong light interaction effects—namely, a pronounced light scattering performance (diffuse transmittance up to ~50%). In addition, the photonic-structured IZO mesh allowed a higher volume of TCO material in the electrode while maintaining the desired transparency, which led to a sheet resistance reduction (by ~30%), thereby providing further electrical benefits due to the improvement of the contact conductance. The results reported herein pave the way for a new class of photonic transparent electrodes endowed with mechanical flexibility that offer strong potential not only as advanced front contacts for thin-film bendable solar cells but also for a much broader range of optoelectronic applications.

Solution processed high performance piezoelectric eggshell membrane – PVDF layer composite nanogenerator via tuning the interfacial polarization

Bio-compatible and eco-friendly flexible piezoelectric nanogenerators with transparency are emerging energy devices for next-generation energy application. A novel high performance natural, biodegradable and flexible eggshell membrane – polyvinylidene difluoride (PVDF) based piezoelectric nanogenerator has been developed using a low-temperature solution and spin coating route. X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman patterns exhibited all characteristic signature peaks of the eggshell membrane and PVDF film. Piezoelectric pristine PVDF, eggshell membrane and eggshell membrane-PVDF layered structure based nanogenerators are fabricated using the flexible ITO coated PET substrate and spin coating technique. The fabricated device of eggshell membrane-PVDF layer exhibited better performance with very high output voltage and current of 15 V and 150 nA as compared to 2 V and 20 nA electric output generation from pristine PVDF film based device under same compressive strain, without electric poling. Dielectric properties of piezoelectric PVDF film and eggshell membrane-PVDF were also measured to analyze the working mechanism of the nanogenerator. Hybrid eggshell membrane-PVDF structure shows very high dielectric constant (260) as compared to pristine PVDF (22). A very high output voltage with an average value of 65 V was also obtained from electrical poled hybrid nanogenerator under force of about 10 kgf. Such high piezoelectric output voltage and current from biodegradable eggshell membrane-PVDF based flexible piezoelectric nanogenerator was attributed to dramatic increase in interfacial polarization, capacitance and improved piezoelectric properties of PVDF and triple helical structure created polarization induced electrical dipole moment in the eggshell membrane lattice. The results not only provide a new way to utilize the solid waste for generating green energy from mechanical vibration but also an agent to increase the performance of the PVDF based nanogenerator for powering next generation self-powered implantable medical devices with reduced e-waste elements.

Flexible P(VDF-TrFE) Shared Bottom Electrode Sensor Array Assisted with Machine Learning for Motion Detection

Lightweight, flexible and distributed-pixel piezoelectric sensors are desired in activity monitoring and human–machine interaction (HMI). In this work, a flexible P(VDF-TrFE) piezoelectric sensor array using ITO-coated PET substrate as the shared bottom electrode is demonstrated. The traditional array fabrication, which connects an individual sensor unit into an array, could easily lead to the signal discrepancy due to fabrication and assembly errors. To this end, this work introduces the shared ITO-coated-PET substrate and proposes a synchronous-fabrication method for generating the same thickness of every P(VDF-TrFE) sensor unit through a single spin coating. The designed Au top electrodes were sputtered on the spin-coated P(VDF-TrFE) to form the sensor array at one time without additional assembly step, further ensuring unit consistency. The performance of the cross-shaped sensor array was tested under cyclic compressing–releasing agitation. The results of the positive compression test show that our sensor array has a high consistency. Then, the cross-shaped array design that covers the central position is put forward, which realizes tactile sensing ability with a small number of units. Moreover, the fabricated flexible multi-pixel sensor has the advantage of sensitive identification of different contact scenes, and a recognition accuracy of 95.5% can be obtained in different types of hand touch through the machine learning technology.

Thermo-optic effects mediated self focusing mechanism and optical power limiting studies of ZnO thin films deposited on ITO coated PET substrates by RF magnetron sputtering under continuous wave laser regime

In this work, ZnO thin films are deposited on ITO coated PET substrates employing RF magnetron sputtering technique. The evolution of crystallites orientation on (002) plane with increasing thickness of the films is unveiled from XRD patterns. Further, the appearance of (103) plane in the highest thickness film (183 nm) is attributed to the formation of surface layer during sputtering process. The smooth and homogenous natures of the films are displayed by the interference pattern in transmittance spectra. The presence of defect level emission in the luminescence spectra is ascribed to compressive stress in the films. The exhibition of orange-red emission confirms the excess oxygen in the sputtered films (89 nm and 183 nm). The dominance of thickness on the third-order nonlinear optical parameters is revealed by single beam Z-scan measurements. The lower thickness ZnO film (42 nm) shows an interesting self focusing behavior under closed aperture Z-scan measurements. A transition from self focusing to self defocusing behavior is noticed with increasing thickness values from 42 nm to 183 nm. The self focusing property is attributed to the combination of presence of large dipole moments at the substrate-film interface as result of large energy gap gradients and thermo-optic effects.

Multidimensional graphene and ZnO-based heterostructure for flexible transparent ultraviolet photodetector

A multidimensional graphene and ZnO-based heterostructure for flexible transparent ultraviolet photodetector (UV-PD) applications is successfully fabricated on an indium tin oxide-coated polyethylene terephthalate substrate (ITO-coated PET). In this prototype, chemically reduced graphene oxide film is used as a charge transfer network and a template layer for the low-temperature growth of high quality vertically aligned zinc oxide nanorods array (ZNRA) on ITO-coated PET substrate. Graphene quantum dots decorated on the ZNRA significantly enhanced the photocurrent of the device. The synergistic effects of the rGO film and GQDs on the performance of the UV-PD are also systematically explored. The fabricated flexible UV-PD shows high detectivity (~1012 cmHz1/2 W−1), high responsivity (~13 AW−1) and good response time (~5 s) at a low bias of 2 V. Importantly, the fabrication process is facile, inexpensive, solution-based, low-temperature (120 °C), and provides a promising platform for flexible transparent UV-PD applications.

Current–voltage characteristics of electrochemically synthesized multi-layer graphene with polyaniline

Abstract Graphene nanosheets (GNS) synthesized through commercially available pencil lead were used to prepare composites with polyaniline on ITO coated PET substrate. I V characteristics of the GNS-PANI composite device shows a decrease in band gap of PANI from 2.8 eV to 6.9 meV at 15 wt% loading of GNS in PANI. SEM and Raman spectroscopy show good dispersion of GNS and interfacial interaction with the GNS-PANI composite by a significant shift in the G peak at 15 wt% GNS-PANI, further confirming the formation of the composite at 15 wt%. Instead of the in-situ polymerization process, the polymer and graphene were mixed externally in the desired concentrations and cast on the substrate directly, thereby offering a good control over the composition of the composite material.

Photovoltaic cells involving the nonconjugated conductive polymer, iodine-doped cis-poly(isoprene)

ABSTRACTNovel photovoltaic cells involving a nonconjugated conductive polymer have been fabricated using titanium dioxide/doped cis-1,4-poly(isoprene)/carbon on ITO coated PET substrates. Photocurrents and photo-voltages for different intensities of light (emission at 300–700 nm) have been measured. These cells have shown significantly higher photocurrents and photo-voltages compared to previous reports. A photocurrent density of about 0.27 mA/cm2 and a photo-voltage of 0.73 V have been measured for a light intensity of ∼4 mW/cm2.

Electrical reliability, multilevel data storage and mechanical stability of MoS2-PMMA nanocomposite-based non-volatile memory device

Molybdenum disulfide (MoS2) is of great interest for its applicability in various optoelectronic devices. Here we report the resistive switching properties of polymethylmethacrylate embedding MoS2 nano-crystals. The devices are developed on an ITO-coated PET substrate with copper as the top electrode. Systematic evaluation of resistive switching parameters, on the basis of MoS2 content, suggests non-volatile memory characteristics. A decent ON/OFF ratio, high retention time and long endurance of 3 × 103, 105 s and 105 cycles are respectively recorded in a device with 1 weight percent (wt%) of MoS2. The bending cyclic measurements confirm the flexibility of the memory devices with good electrical reliability as well as mechanical stability. In addition, multilevel storage has been demonstrated by controlling the current compliance and span of voltage sweeping in the memory device.

A stability study of roll-to-roll processed organic photovoltaic modules containing a polymeric electron-selective layer

The stability of roll-to-roll processed organic photovoltaic modules having an inverted structure and incorporating polyethylenimine–ethoxylate (PEIE) as the electron-selective layer was investigated. Large-area modules were fabricated on ITO-coated PET substrates using roll-to-roll coating and printing methods. Modules were encapsulated with commercially-available ultra-high gas/vapor barrier films by employing new encapsulation protocols developed during this work. The operational lifetime of modules on storage in an environmental chamber at ambient temperature and relative humidity of 35°C and 50%, respectively, and under continuous simulated AM1.5G illumination was found to increase by more than three orders of magnitude upon encapsulation. The chemical stability of the PEIE films under these storage conditions was also studied. Fracture tests were conducted on modules exposed to the same storage conditions to investigate the effects on inter- and intra-layer adhesion and cohesion. An increase in adhesive strength was found for the exposed devices indicating an absence of any substantial mechanical degradation of the deposited layers for the exposure conditions used during this work. The results described here demonstrate the potential utility of commercially-available PEIE as a convenient and effective organic electron-selective layer for the fabrication of durable roll-to-roll processed organic solar cell devices.

Photovoltaic Cells Involving the Nonconjugated Conductive Polymer Iodine-Doped Styrene-Butadiene-Rubber (SBR)

Novel photovoltaic cells involving a nonconjugated conductive polymer have been fabricated using titanium dioxide/doped styrene-butadiene-rubber/carbon on ITO coated PET substrates. Photocurrents and photo-voltages for different intensities of light (emission at 300–700 nm) have been measured. These cells have shown significantly higher photocurrents and photo-voltages compared to previous reports. A photocurrent density of about 0.25 mA/cm2 and a photo-voltage of 0.74 V have been measured for a light intensity of ∼4 mW/cm2.

Integrated OLED as excitation light source in fluorescent lateral flow immunoassays.

The integration of organic light emitting diodes (OLEDs) as excitation light sources for quantum dot-based fluorescent lateral flow immunoassay systems (LFIA) was investigated. This approach has the potential to deliver a sensitive visible detection scheme for low-cost, disposable lab-on-chip point-of-care (POC) diagnosis system. Thin film phosphorescent green OLEDs fabricated on plastic substrates were integrated on-chip to excite the test line of a quantum dot-based LFIA (QD-LFIA). OLEDs were fabricated by sequential deposition of organic thin films (total of ~100 nm) onto ITO-coated PET substrates. CdSe/ZnS QDs emitting at 655 nm and Au nanoparticles (NP - 10 nm size) conjugated antibodies were used for the fluorescence QD-LFIA and conventional reflection-mode Au NP-LFIA, respectively. Thin plastic color light filters were integrated for filtering the excitation light source and, thereby, increasing the contrast of the emitted light for optimized visual detection. Integration of the OLED and color filters with the analytical membrane was achieved using adhesive techniques facilitated by the planar nature of the layers, which suggests possible large scale manufacturing using roll-to-roll processing. Gray scale analysis from digital images captured with a digital camera was used to quantify the visual sensitivity. The signal intensity, signal-to-noise ratio (SNR) and the limit of detection (LOD) of OLED integrated QD-LFIAs were compared to Au NP LFIAs. OLED QD-LFIA exhibited superior performance in all signal aspects: 7-8× higher signal intensity and SNR, and a 7× lower LOD of 3 nM (measured at S/N=3). These results demonstrate the potential of OLED-integrated in LFIA devices for obtaining sensitive, fast and low-cost POC diagnostics.

Quantum dot-based sensor layer in lightweight structures

Quantum dots can be used to detect, store and make visually apparent mechanical loading conditions. The fluorescent properties of the nanocrystals are selectively influenced by the injection of electric charges. By applying an external electric voltage, it is possible to suppress photoluminescence completely. If the quantum dots, as part of a functional layer system, are integrated in smart components, the integrated material system allows for energy-autonomous condition monitoring. We present for the first time a quantum dot-based system in a glass fiber-reinforced epoxy composite with a layer structure which is suitable for impact visualization. The quantum dots dispersed in poly (9-vinylcarbazoles) were applied on a PEDOT:PSS layer on an ITO-coated PET substrate. Silver electrodes were sputtered as a structured layer. For integration of the layer stack, which measured 25×25×0.1mm, in an epoxy composite, two process variants and sample geometries were used: a 2D curved component for hand lay-up and a plate for resin transfer molding. The epoxy composite components had a material thickness of 1.5mm and included eight layers of fiberglass cloth. The quantum dot-layer stacks were positioned either between the first two layers of glass fiber or directly at the component surface which had only a thin epoxy layer. By applying an external voltage, we suppressed the photoluminescence of the integrated quantum dots; the suitability of the coating system for integrated material sensors was evident.

Flexible ITO-free polymer solar cells based on highly conductive PEDOT:PSS and a printed silver grid

We report efficient flexible polymer solar cells based on ITO and ITO-free semi-transparent electrodes consisting of either a highly conductive PEDOT:PSS formulation (PH1000) or a combination of printed silver grids and PH1000. As active layer material a polymer:fullerene bulk heterojunction based on PCDTBT:PC70BM (poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:phenyl-C71-butyric acid methyl ester) was used. We demonstrate that the printed silver grid in combination with PH1000 leads to comparative device performances as ITO-coated PET substrates and has the potential for more.

Effect of Bending on the Spectrum of Backlight Transmitted Through Flexible ITO/PET Substrate

Flexible displays and electronics fascinate the researchers all around the globe due to their less thickness and light weight. ITO coated PET substrate is the most commonly used flexible substrate for fabricating organic and polymeric electronic and photonic devices for future displays and light sources. Due to the presence of residual stress and other defects, the electro-optical characterization of these substrates is essential. In this paper, we report the measurement of spectral properties of light transmitted through ITO/PET substrate. Spectral changes and modulations were observed on bending the PET substrate. Experimental results of spectral changes and modulations using the R, G, B, and W LEDs as well as broad band halogen source are reported. CIE coordinates were also reported for the change in the spectral profile. Spectral changes in presence of flexible substrate are attributed due to residual stress and due to bending the substrate leading to change in refractive index.

Characterization of Phosphoric Acid Doped N-type Silicon Thin Films Printed on ITO Coated PET Substrate

Characterization of Phosphoric Acid Doped N-type Silicon Thin Films Printed on ITO Coated PET Substrate