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Printed organic sensors are of significant importance owing to their simplicity, low cost, easy fabrication and solution processability. However, organic sensors often face the problem of performance degradation when exposed to ambient environment therefore, the effect of humidity needs to be studied for prolonging the lifetime of organic sensors. In this study, we propose atomically thin and highly reliable encapsulation layer on the surface of an organic functional material to enhance its lifetime as a temperature sensing unit. Our organic temperature sensor is based on a conductive and uniform IDT pattern deposited on a glass substrate through advanced printing technology of reverse offset. Thin film of PEDOT:PSS is used as the temperature sensitive functional layer deposited through electrohydrodynamic atomization while the organic thin film was encapsulated with aluminum oxide (Al2O3) through spatial atmospheric atomic layer deposition system (SAALD). The temperature range of the developed sensors was from 25 to 90 °C with relative humidity reaching up to 75% RH. The obtained results exhibited that Al2O3 encapsulation deposited through SAALD significantly enhanced the linearity, repeatability, endurance (50 cycles), retention (1 month) and lifetime of organic temperature sensor as compared to the non-encapsulated sensor. The performance degradation mechanism of non-encapsulated sensor due to humid environment has been discussed in detail. This study contributes an important step forward for preserving the performance and elongating the lifetime of organic electronic devices through a single atomically thin encapsulation. [ABSTRACT FROM AUTHOR]

Large area organic light emitting diode (OLED) has been fabricated on flexible polyethylene terephthalate (PET) substrate using electrohydrodynamics spray system with active area of 3 × 3 cm. This solution processing of organic inks and quantum dots is performed at room temperature and atmospheric pressure in a single step processing compatible with roll-to-roll processing system. The thin film characterizations are performed by SEM, TEM, spectroscopes and semiconductor device analyzer. CdSe/ZnS quantum dots are used as emissive layer while PEDOT:PSS and MEH-PPV are used as hole and electron transport layers. OLED produced red light at the wavelength of 634 nm. A life time of 1 h at 0.3 lx was achieved by the OLED device. [ABSTRACT FROM AUTHOR]

This paper describes synthesis of graphene/poly(4-vinylphenol) (PVP) nanocomposite and deposition of thin film by electrohydrodynamic atomization (EHDA) for fabrication flexible resistive switching device. EHDA technique proved its viability for thin film deposition after surface morphology analyses by field emission scanning electron microscope (FESEM) and non-destructive 3D Nano-profilometry, as the deposited films were, devoid of abnormalities. The commercially available graphene micro-flakes were exfoliated and broken down to ultra-small (20 nm–200 nm) nano-flakes by ultra-sonication in presence of N-methyl-pyrrolidone (NMP). These graphene nanoflakes with PVP nanocomposite, were successfully deposited as thin films (thickness ~140±7 nm, R a =2.59 nm) on indium–tin-oxide (ITO) coated polyethylene terephthalate (PET) substrate. Transmittance data revealed that thin films are up to ~87% transparent in visible and NIR region. Resistive switching behaviour of graphene/PVP nanocomposite thin film was studied by using the nanocomposite as active layer in Ag/active layer/ITO sandwich structure. The resistive switching devices thus fabricated, showed characteristic OFF to ON (high resistance to low resistance) transition at low voltages, when operated between ±3 V, characterized at 10 nA compliance currents. The devices fabricated by this approach exhibited a stable room temperature, low power current–voltage hysteresis and well over 1 h retentivity, and R OFF / R ON ≈35:1. The device showed stable flexibility up to a minimum bending diameter of 1.8 cm. [ABSTRACT FROM AUTHOR]

Emerging resistive switching devices are believed to play a vital role in realizing ultra-dense nanocrossbar arrays for the next generation mass storage memory. This work reports the resistive switching effect in organic-inorganic hybrid nanocomposite of perovskite oxide zinc stannite nanocubes (ZnSnO 3 NCs) and a polymer Poly(methyl methacrylate) (PMMA). The functional layer was sandwiched between indium tin oxide (ITO) and silver (Ag) electrodes on a flexible PET substrate. The obtained electrical results clearly exhibited that the addition of PMMA in ZnSnO 3 NCs enhanced electrical endurance (500 biasing cycles), retention time (∼10 4 s), switching ratio (∼10 3 ) and repeatability of our memory device. Moreover the effect of device size on the resistive switching characteristics of this hybrid nanocomposite is also explored by varying the diameter of top electrode. The whole device fabrication except bottom layer was done through all printed technology such as electrohydrodynamic atomization (EHDA) and inkjet reciprocating head. The developed memory device displayed characteristic bipolar, nonvolatile and rewritable memory behavior at a low operating voltage. The obtained results of chemical, structural, electrical and surface morphology are added to completely understand the impact of adding a polymer on the switching characteristics of perovskite NCs. [ABSTRACT FROM AUTHOR]

In this study, organic polymer poly-vinyl acetate (PVA) and inorganic aluminum oxide (Al 2 O 3 ) have been used together to fabricate a hybrid barrier thin film for the protection of PET substrate. The organic thin films of PVA were developed through roll to roll electrohydrodynamic atomization (R2R-EHDA) whereas the inorganic thin films of Al 2 O 3 were grown by roll to roll spatial atmospheric atomic layer deposition (R2R-SAALD) for mass production. The use of these two technologies together to develop a multilayer hybrid organic-inorganic barrier thin films under atmospheric conditions is reported for the first time. These multilayer hybrid barrier thin films are fabricated on flexible PET substrate. Each layer of Al 2 O 3 and PVA in barrier thin film exhibited excellent morphological, chemical and optical properties. Extremely uniform and atomically thin films of Al 2 O 3 with average arithmetic roughness (Ra) of 1.64 nm and 1.94 nm respectively concealed the non-uniformity and irregularities in PVA thin films with Ra of 2.9 nm and 3.6 nm respectively. The optical transmittance of each layer was ∼ 80-90% while the water vapor transmission rate (WVTR) of hybrid barrier was in the range of ∼ 2.3 × 10 −2 g m −2 day −1 with a total film thickness of ∼ 200 nm. Development of such hybrid barrier thin films with mass production and low cost will allow various flexible electronic devices to operate in atmospheric conditions without degradation of their properties. [ABSTRACT FROM AUTHOR]