Transparent and flexible electronics are emerging technologies with the potential to enable new applications. However, to ensure high‐performance transparent electronics, post‐processing such as ...thermal annealing and vacuum plasma treatment is necessary, which are difficult to apply to polymer‐based flexible substrates. This study analyzed the feasibility of applying selective Ar plasma jet treatment at atmospheric pressure to transparent flexible electronics. When atmospheric Ar plasma treatment is applied to transparent flexible aluminum‐doped zinc oxide (AZO), it showed a maximum 83.1% improvement in sheet resistance while maintaining a high transmittance performance, of over 70%. To verify the mechanism behind the surface treatment effect using atmospheric Ar plasma, comprehensive analyses are performed using atomic force microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy, which confirmed that the effect is due to oxygen vacancy formation caused by ion bombardment and thermal diffusion. The application of atmospheric plasma treatment to a patterned transparent flexible AZO device resulted in a reduction in contact resistance, and it is confirmed that the performance improvement effects can be retained for >500 h by applying additional passivation.
In this study, a high‐performance transparent flexible AZO electrode fabricated using a novel plasma jet‐based surface treatment technology that is applicable at room temperature and atmospheric pressure. Unlike conventional high‐temperature thermal annealing methods, the atmospheric plasma jet can be applied to flexible substrates and can improve the sheet resistance of AZO electrodes by up to 83.1%.
Increasing demand for real-time healthcare monitoring is leading to advances in thin and flexible optoelectronic device-based wearable pulse oximetry. Most previous studies have used OLEDs for this ...purpose, but did not consider the side effects of broad full-width half-maximum (FWHM) characteristics and single substrates. In this study, we performed SpO
measurement using a fiber-based quantum-dot pulse oximetry (FQPO) system capable of mass production with a transferable encapsulation technique, and a narrow FWHM of about 30 nm. Based on analyses we determined that uniform angular narrow FWHM-based light sources are important for accurate SpO
measurements through multi-layer structures and human skin tissues. The FQPO was shown to have improved photoplethysmogram (PPG) signal sensitivity with no waveguide-mode noise signal, as is typically generated when using a single substrate (30-50%). We successfully demonstrate improved SpO
measurement accuracy as well as all-in-one clothing-type pulse oximetry with FQPO.
Abstract Stretchable displays attract significant attention because of their potential applications in wearable electronics, smart textiles, and human-conformable devices. This paper introduces an ...electrically stable, mechanically ultra-robust, and water-resistant stretchable OLED display (SOLED) mounted on a stress-relief pillar platform. The SOLED is fabricated on a thin, transparent polyethylene terephthalate (PET) film using conventional vacuum evaporation, organic-inorganic hybrid thin film encapsulation (TFE), and a nonselective laser patterning process. This simple and efficient process yields an OLED display with exceptional stretchability, reaching up to 95% strain and outstanding durability, enduring 100,000 stretch-release cycles at 50% strain. Operational lifetime and water-resistant storage lifetime measurements confirm that the TFE provides effective protection even after the nonselective laser patterning process. A 3 × 3 array SOLED display module mounted on a stress-relief pillar platform is successfully implemented, marking the first case of water-resistant display array operation in the field of SOLEDs. This work aims to develop practical stretchable displays by offering a reliable fabrication method and device design for creating mechanically robust and adaptable displays, potentially paving the way for future advances in human-conformable electronics and other innovative applications.
Free-form factor optoelectronics is becoming more important for various applications. Specifically, flexible and transparent optoelectronics offers the potential to be adopted in wearable devices in ...displays, solar cells, or biomedical applications. However, current transparent electrodes are limited in conductivity and flexibility. This study aims to address these challenges and explore potential solutions. For the next-generation transparent conductive electrode, Al-doped zinc oxide (AZO) and silver (AZO/Ag/AZO) deposited by in-line magnetron sputtering without thermal treatment was investigated, and this transparent electrode was used as a transparent organic light-emitting diode (OLED) anode to maximize the transparency characteristics. The experiment and simulation involved adjusting the thickness of Ag and AZO and OLED structure to enhance the transmittance and device performance. The AZO/Ag/AZO with Ag of 12 nm and AZO of 32 nm thickness achieved the results of the highest figure of merit (FOM) (Φ
= 4.65 mΩ
) and lowest roughness. The full structure of transparent OLED (TrOLED) with AZO/Ag/AZO anode and Mg:Ag cathode reached 64.84% transmittance at 550 nm, and 300 cd/m
at about 4 V. The results demonstrate the feasibility of adopting flexible substrates, such as PET, without the need for thermal treatment. This research provides valuable insights into the development of transparent and flexible electronic devices.
Bottom-gate thin-film transistors (TFTs) with n-type amorphous indium-gallium-zinc oxide (a-IGZO) active channels and indium-tin oxide (ITO) source/drain electrodes were fabricated. Then, an ...ultraviolet (UV) nanosecond pulsed laser with a wavelength of 355 nm was scanned to locally anneal the active channel at various laser powers. After laser annealing, negative shifts in the threshold voltages and enhanced on-currents were observed at laser powers ranging from 54 to 120 mW. The energy band gap and work function of a-IGZO extracted from the transmittance and ultraviolet photoelectron spectroscopy (UPS) measurement data confirm that different energy band structures for the ITO electrode/a-IGZO channel were established depending on the laser annealing conditions. Based on these observations, the electron injection mechanism from ITO electrodes to a-IGZO channels was analyzed. The results show that the selective laser annealing process can improve the electrical performance of the a-IGZO TFTs without any thermal damage to the substrate.
Organic light‐emitting diodes (OLEDs) and polymer light‐emitting diodes (PLEDs) are considered promising devices in that they are not limited to conventional display devices and can provide versatile ...functions in photomedicine. Many attempts to replace rigid photomedicine devices with wearable light‐emitting devices are in progress, and OLEDs have shown feasibility with respect to device conformality and photo‐medical efficiency. This paper presents a newly designed flexible optoelectronic device utilizing a wavelength‐designable PLED as an option for realizing disposable photomedicine devices. An optical design based on a multilayer electrode and an additional injection unit is proposed; it allows control of the device peak wavelength without any deterioration of charge injection. Furthermore, a sandwich structure utilizing transferable thin‐film encapsulation enables the PLED to achieve mechanical flexibility, low device heat generation, and sufficient operational lifetime (>8 h). When fibroblasts are irradiated by the wavelength‐designable PLED with a 630 nm peak, cell proliferation and production of type‐I procollagen increase by 25% and 36%, respectively. The change of matrix metalloproteinase‐1 is also evaluated, and it is found to decrease by 23%. Based on these results, the wavelength‐designable PLED induces distinct changes of biological factors.
Flexible and wavelength‐designable polymer light‐emitting diodes are demonstrated and the in vitro test for human fibroblasts is carried out to prove their feasibility to skin rejuvenation. When fibroblast cells are irradiated by the suggested devices, the fibroblast proliferation and production of type‐I procollagen increase by 25% and 36%, respectively, and the matrix metalloproteinase‐1 decrease by 23%.
It is extremely rare that near‐infrared organic light‐emitting diodes (NIR OLEDs) have been actually applied to various fields such as sensors, night‐vision displays, or phototherapy owing to device ...reliability and stability. Therefore, developing a novel deep red to NIR (DR/NIR) emitter for the high‐performance DR/NIR OLED has become a prominent research area. Herein, a novel thienothiophene‐isoquinoline‐based Ir(III) complex DR/NIR emitter with narrow full width half maximum (FWHM, 38 nm), a shallow highest occupied molecular orbital (HOMO) energy level, and short radiative lifetime of 0.66
μs
is designed and synthesized. The best device based on a new Ir(III) complex yields record‐high radiant emittance (> 5 mW cm−2) at low voltage (6 V), low external quantum efficiency (EQE) roll‐off, low driving voltage (2.5–6 V), and stable operational lifetime for biomedical application with an emission peak wavelength of 696 nm. From all perspectives, this is notably an outstanding performance among other reported Ir(III)‐based DR/NIR OLEDs. Moreover, DR/NIR OLEDs are applied to the biomedical field and an in vitro experiment shows an increase in cell proliferation effect of up to 24% under diverse conditions.
Deep red to near‐infrared organic light‐emitting diodes based on a novel Ir complex are fabricated with different host materials and structures, and the best device presents high radiant emittance (> 5 mW cm−2) at low driving voltage.
The vacuum process using small molecule-based organic materials to make organic photodiodes (OPDIs) will provide many promising features, such as well-defined molecular structure, large scalability, ...process repeatability, and good compatibility for CMOS integration, compared to the widely used Solution process. We present the performance of planar heterojunction OPDIs based on pentacene as the electron donor and C60 as the electron acceptor. In these devices, MoO3 and BCP interfacial layers were interlaced between the electrodes and the active layer as the electron- and hole-blocking layer, respectively. Typically, BCP played a good role in suppressing the dark current by two orders higher than that without that layer. These devices showed a significant dependence of the performance on the thickness of the pentacene. In particular, with the pentacene thickness of 25 nm, an external quantum efficiency at the 360 nm wavelength according to the peak absorption of C60 was enhanced by 1.5 times due to a cavity effect, compared to that of the non-cavity device. This work shows the importance of a vacuum processing approach based on small molecules for OPDIs, and the possibility of improving the performance via the optimization of the device architecture.
Al
2
O
3
films have long been widely used as inorganic encapsulation or passivation layers. The Al
2
O
3
single layer, however, exhibits not only a relatively low barrier performance but also poor ...environmental stability under harsh conditions due to its hydrolysis reaction with water vapor. Thus, to further improve its environmental reliability and barrier performance as a gas diffusion barrier (GDB), the GDB should be newly designed by forming a nanolaminate structure with ultra-thin sublayers. In addition, through the use of a multilayer based on nanolaminate/organic layers, the nanolaminate film can be effectively protected by a SiO
2
-inserted organic layer. In this study, alternately stacked nanolaminate/silane-based organic layers are proposed. The nanolaminate-based multilayer achieved a water vapor transmission rate (WVTR) of 5.94 × 10
−5
g/m
2
/day under 60°C/90% accelerated conditions. In addition, after a bending test, the nanolaminate-based multilayer showed a WVTR increase by a magnitude of one order under a 0.63% bending strain. The proposed environmentally and mechanically stable hybrid thin-film encapsulation offers a strong potential for the realization of washable, wearable, or flexible displays in the future.
This study focuses on investigating the doping effect of molybdenum oxide (MoOX) on a p-type organic dinaphtho2,3-b:2′,3′-fthieno3,2-bthiophene (DNTT) thin-film transistor (TFT) and its implications ...for various electronic applications. Specifically, we examined the influence of the doping position of MoOX on the transistor performance. When MoOX was doped between the electrode and the semiconductor (ME-OTFT), it facilitated charge injection by reducing the surface roughness. Consequently, the on-current and mobility of the ME-OTFT slightly increased compared to the undoped device. Additionally, when MoOX was fully covered on the ME-OTFT (MF-OTFT), it caused hole accumulation at the interface between DNTT and MoOX, forming a top channel. As a result, the off-current significantly increased, leading to an on-off ratio of 8.74 A/A, indicating the operation in depletion mode. Furthermore, we successfully demonstrated p-type unipolar inverters using the MF-OTFT as a pull-down device and the DNTT TFT as a pull-up device. Specifically, we implemented a zero-VGS connection inverter and a diode connection inverter with a maximum voltage gain of 22.06 V/V. The findings contribute to a deeper understanding of the effects of MoOX doping and its potential for enhancing device performance in unipolar circuits applications.
Display omitted
•Exploration of the charge flow mechanism based on the positioning of MoOX doping.•Comprehensive spectroscopic analysis of the doping effects of MoOX.•Present findings on a fully-doped transistor with depletion mode using MoOX.•Investigate the impact of doping on unipolar inverter circuits (zero-VGS connection inverter and diode connection inverter).
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