Remote plasma-enhanced atomic layer deposition (R-PEALD) of zirconium dioxide (ZrO2) experiments were conducted using tetrakis(dimethylamino)zirconium (TDMAZ) with O2 plasma as the oxidant. The reaction mechanisms of ZrO2 were studied using in situ quartz crystal microbalance (QCM) and in situ quadrupole mass spectroscopy (QMS). QMS revealed typical combustion byproducts such as CO2, CO, NO, and H2O during the O2 plasma process. In addition, Fourier transform infrared spectroscopy (FTIR) measurements were used to identify the bonds present in the thin film at different deposition temperatures. In our previous work, it was found that an increase in temperature resulted in a reduction of impurities in thin films. The influence of the deposition temperature on several possible surface reaction characteristics of the plasma process was studied. Such characteristics included composition of the film and growth per cycle. In particular, it was first demonstrated that the −C≡N group gave rise to cutoff phenomenon at high temperature. Several reaction pathways were accordingly established. The present work initiates a new way of achieving controlled growth properties of ZrO2 thin films.

•A new method to fabricate transparent electrodes for flexible OLEDs.•Inkjet-printing of Ag ink on AgNW produces highly conductive transparent electrodes.•The maximum brightness and current efficiency are similar to ITO based OLEDs.•The printed hybrid electrode has superior flexibility than ITO-based OLEDs.Networks of silver nanowires (AgNW) have been shown to facilitate high transparency, high conductivity, and good mechanical stability. However，the loose characteristic and local insulation problems due to gaps between the nanowires limit their application as electrodes. This study investigates an inkjet-printed Ag grid combined with AgNW to form a transparent hybrid electrode. The printed Ag grid on AgNW film connects the gaps between the Ag nanowires to increase the overall electric conductivity. The printed Ag-grid/AgNW hybrid electrodes have low resistivity (22.5 Ω/□) while maintaining a high transmittance (87.5%). These values are similar to standard indium tin oxide (ITO) on glass which has resistivity of 20Ω/□ and transmittance of 89% at 550 nm. In addition, these hybrid electrodes are also very flexible when fabricated on a photopolymer substrate. A spin-coating process combined with a peel-off process enable the fabrication of flexible ultra-smooth Ag-grid/AgNW electrodes. We tested the transparent and flexible electrode as the anode of a flexible organic light emitting diode (F-OLED). The light emitting layer of the F-OLED is 35 nm thick tris-(8-hydroxyquinoline) aluminum doped with 0.5% 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyropyrano(6,7-8-I,j)quinolizin-11-one. The maximum brightness and current efficiency of the F-OLED are 10000 cd/m2 and 12 cd/A, respectively, even when bent around a radius of 2 mm. The good performance of the device with Ag-grid/AgNW hybrid electrodes show that enhanced conductive inkjet-printed Ag nanoparticles combined with Ag nanowires can produce high quality electrodes for flexible organic optoelectronic devices.

•Firstly introduced MCP and B4PYMPM and their application in OLEDs and get peak power efficiency of 71.3 lm/W for WOLEDs.•We have successfully demonstrated efficient blue OLEDs which used MCP and B4PYMPM as the mixed-host with a maximum efficiency of 27.30 lm/W (29.24 cd/A).•Based on the blue EML, we realized WOLEDs, characterized by a peak power efficiency of 71.3 lm/W at 3.1 V and a low turn-on voltage of 2.65 V.In this study, we demonstrate a high-efficiency and low turn-on voltage warm white phosphorescent organic light emitting devices (PH-WOLEDs) based on a blue mixed-host emission layer (EML) and an orange ultrathin layer. The device has a simple structure and would simplify the fabrication process and reduce fabrication costs. The concept is based on the design a high-efficiency blue mixed-host EML, using an electron-transport material, 4,6-Bis(3,5-di(pyridin-4-yl) phenyl)-2-(3-(pyridin-3-yl) phenyl) pyrimidine (B4PYMPM) to enhance the carrier balance ability of the hole-transport material 1,3-Bis(carbazol-9-yl) benzene (MCP) which operates as the mixed-host and when the MCP: B4PYMPM ratio in the mixed-film was 4:1 got better effects. Based on the blue EML, we realized WOLEDs, characterized by a peak power efficiency of 71.3 lm/W at 3.1 V and a low turn-on voltage of 2.65 V. The mixed-host blue EML exhibited a much higher performance compared to the MCP host. Stable warm white light emission with Commission International de L'Eclairage (CIE) coordinates from (0.37, 0.45) to (0.38, 0.47) for a luminance value ranging from 1000 to 10,000 cd/m2 was obtained.Download high-res image (252KB)Download full-size image

Among the advanced electronic devices, flexible organic electronic devices with rapid development are the most promising technologies to customers and industries. Organic thin films accommodate low-cost fabrication and can exploit diverse molecules in inexpensive plastic light emitting diodes, plastic solar cells, and even plastic lasers. These properties may ultimately enable organic materials for practical applications in industry. However, the stability of organic electronic devices still remains a big challenge, because of the difficulty in fabricating commercial products with flexibility. These organic materials can be protected using substrates and barriers such as glass and metal; however, this results in a rigid device and does not satisfy the applications demanding flexible devices. Plastic substrates and transparent flexible encapsulation barriers are other possible alternatives; however, these offer little protection to oxygen and water, thus rapidly degrading the devices. Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation into the flexible devices. Because of these (and other) reasons, there has been an intense interest in developing transparent barrier materials with much lower permeabilities, and their market is expected to reach over $550 million by 2025. In this study, the degradation mechanism of organic electronic devices is reviewed. To increase the stability of devices in air, several TFE technologies were applied to provide efficient barrier performance. In this review, the degradation mechanism of organic electronic devices, permeation rate measurement, traditional encapsulation technologies, and TFE technologies are presented.

•An exciplex/phosphorescence hybrid white OLED was fabricated for the first time with blue/orange complementary emitters.•By using exciplex as the blue emitter, non-radiative triplet-states on the exciplex can be harvested for light-emission by transferring them to low triplet-state phosphors.In this study, a highly efficient fluorescent/phosphorescent white organic light-emitting device (WOLED) was fabricated using exciplex light emission. The hole-transport material 4,4ʹ,4ʺ-tris(N-carbazolyl)triphenylamine (TCTA), and electron-transport material, 4,7-diphenyl-1,10-phenanthroline (Bphen), were mixed to afford a blue-emitting exciplex. The WOLED was fabricated with a yellow phosphorescent dye, Ir(III) bis(4-phenylthieno [3,2-c] pyridinato-N,C2ʹ) acetylacetonate (PO-01), combined with the exciplex. In this structure, the energy can be efficiently transferred from the blend layer to the yellow phosphorescent dye, thus improving the efficiency of the utilization of the triplet exciton. The maximum power efficiency of the WOLED reached a value 9.03 lm/W with an external quantum efficiency of 4.3%. The Commission Internationale de I'Eclairage (CIE) color coordinates (x,y) of the device were from (0.39, 0.45) to (0.27, 0.31), with a voltage range of 4–9 V.

In this study, ZrO2 films deposited by the atomic layer deposition method, as the encapsulation layer for organic electronics devices, were characterized. Both the effects of tetrakis (dimethylamido) zirconium(IV) growth temperature and oxidants, such as water (H2O) and ozone (O3), were investigated. The X-ray diffraction analysis shows the amorphous characteristic of the 80-nm-thick films grown at 80 °C, the crystallinity of the films was much lower than those grown at 140 and 200 °C. The scanning electron microscopy analyses showed that the surface morphology strongly depended on the crystallinity of the film. The water vapor transmission rate of the 80 nm thick ZrO2 films can be reduced from 3.74 × 10–3 g/(m2 day) (80 °C–H2O as the oxidant) to 6.09 × 10–4 g/(m2 day) (80 °C–O3 as the oxidant) under the controlled environment of 20 °C and a relative humidity of 60%. Moreover, the organic light-emitting diodes integrated with 80 °C–O3-derived ZrO2 films were undamaged, and their luminance decay time changed considerably. This was attributed to the better barrier property of the low-temperature ZrO2 film to the amorphous microscopic bulk and almost homogeneous microscopic surface.Keywords: atomic layer deposition; crystalline state; ozone oxidant; thin-film encapsulation; water vapor transmission rate; zirconium oxide;

•[Al2O3:Alucone] films were fabricated by low temperature atomic/molecule layer deposition method.•Inorganic–organic nanolaminate structure allows the optical properties to be tuned.•[Al2O3:Alucone] encapsulation layers improved the lifetime of TEOLEDs.The optical and barrier properties of thin-film encapsulations (TFEs) for top-emitting organic light-emitting diodes (TEOLEDs) were investigated using TFEs fabricated by stacking multiple sets of inorganic–organic layers. The inorganic moisture barrier layers were prepared by atomic layer deposition (ALD) of Al2O3 using trimethylaluminum (TMA) and O3 as precursors and are shown to be efficient barriers against gases and vapors. The organic alucone layers were produced by molecular layer deposition (MLD) using TMA and ethylene glycol as precursors. The [Al2O3:Alucone] ALD/MLD films were used because their adjustable inorganic–organic nanolaminate composition allows for the tuning of the optical properties, thereby enhancing their application potential for the design and fabrication of high performance light out-coupling structures for TEOLEDs. By carefully adjusting the relative thickness ratio of the inorganic–organic encapsulation materials, optimized light extraction was achieved and the films not only maintained their high moisture barrier strength but also showed excellent optical performance.

The investigations reported in this study were carried out to determine the feasibility and properties of alucone/Al2O3 hybrid nanolaminate films for thin film encapsulation (TFE) at low temperature, using an integrated molecular layer deposition (MLD) and atomic layer deposition (ALD) process. The combination of alucone (MLD) and Al2O3 (ALD), with O3 serving as the oxidant in place of conventional H2O, has been evaluated experimentally. In our studies, O3-based encapsulation layers were observed to be smoother, displaying an average roughness of 0.342 ± 0.016 nm with three laminate layers. However, H2O-based laminates showed a much higher roughness of 0.843 ± 0.024 nm under identical conditions. Estimates of water vapor transmission rate (WVTR) yielded significantly better results for O3-based laminates, with values decreasing linearly from 3.22 × 10−3 g m−2 per day to 2.37 × 10−5 g m−2 per day as the number of laminate layers increased from one to three, while a gentle decline trend from 1.83 × 10−3 g m−2 per day to 5.92 × 10−4 g m−2 per day was obtained for the H2O-based laminate. This indicates that the hybrid nanolaminates exhibited improved water barrier properties when O3 was used as the oxidant instead of H2O. In particular, the O3-based films did not decrease the performance of organic light-emitting diodes (OLEDs). In fact, the lifetime of OLEDs with O3-based encapsulation was approximately two-fold longer than the H2O-based encapsulation. Thus, we believe that the alucone/Al2O3 hybrid encapsulation film, in which O3 serves as the oxidant, is a promising candidate for use in future OLED applications.

•Al2O3 film fabricated by ALD at low temperature was prepared as high barrier layer for TE-OLED.•The light extraction of TE-OLED was enhanced by coating Al2O3 layer on the transparent Ag cathode.•O3 was used as precursor of ALD to deposit Al2O3 thin film.This paper reported a low-temperature thin film encapsulation (TFE) process based on atomic layer deposition Al2O3 layer for top-emission organic light-emitting devices (TE-OLEDs). The barrier characteristics of both H2O-based and O3-based Al2O3 films were investigated. O3-based Al2O3 TFE showed lower water vapor transmission rate (WVTR) of 8.7 × 10−6 g/m2 day and longer continuous operation lifetime of 5 folds compared to the device with H2O-based Al2O3 TFE under identical environmental and driving conditions. Furthermore, the extraction of emitting light of the devices with barrier layer was enhanced compared to the bared one. The theory simulation data were consistent with our experimental results and showed the potential for the design of TFE structures optimized for enhancing light transmission.

We investigated Al2O3 atomic layer deposition growth layer for encapsulation of organic light emitting diodes (OLEDs). It was found that surface properties of these O3-based Al2O3 were superior to those of H2O based Al2O3 grown at relative higher temperatures. Therefore, the water vapor transmission rate of ∼60 nm thick Al2O3 films can be reduced from 4.9 × 10–4 g/(m2 day) (80 °C–H2O) to 8.7 × 10–6 g/(m2 day) (80 °C–O3) under a controlled environment of 20 °C and relative humidity of 60%. Besides, the OLEDs integrated with 80 °C–O3 based Al2O3 film were undamaged, and their luminance decay time was altered to a considerable extent.