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Metal halide perovskites have been actively studied as promising materials in optoelectronic devices because of their superior optical and electrical properties and have also shown considerable potential for flexible devices because of their good mechanical properties. However, the large hole injection barrier and exciton quenching between the perovskite emitter and poly(3,4-ethylenedioxythiophene):poly-styrene sulfonate (PEDOT:PSS) can lead to the reduction in device efficiency. Here, a nonconductive fluorosurfactant, Zonyl FS-300 (Zonyl), is introduced into the PEDOT:PSS hole transport layer, which reduces the hole injection barrier and exciton quenching at the PEDOT:PSS/perovskite interface. Moreover, a flexible perovskite light-emitting diode with a polymer-silver nanowire composite electrode is demonstrated, showing a maximum current efficiency (CEmax) of 17.90 cd A-1, and this is maintained even after 1000 cycles of bending with a 2.5 mm bending radius.

A novel flexible transparent electrode (TE) having a trilayer-stacked geometry and high optoelectronic performance and operational stability was fabricated by the spin coating method. The trilayer was composed of an ultrathin graphene (Gr) film sandwiched between a transparent and colorless polyimide (TCPI) layer and a methanesulfonic acid (MSA)-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer containing dimethylsulfoxide and Zonyl fluorosurfactant (designated as MSA-PDZ film). The introduction of solution-processable TCPI enabled the direct formation of high-quality graphene on organic surfaces with a clean interface. Stable doping of graphene with the MSA-PDZ film enabled tuning of the inherent work function and optoelectronic properties of the PEDOT:PSS films, leading to a high figure of merit of ∼70 in the as-fabricated TEs. Particularly, from multivariate and repetitive harsh environmental tests ( T = -50 to 90 °C, over 90 RH%), the TCPI/Gr heterostructure exhibited excellent tolerance to mechanical and thermal stresses and gas barrier properties that protected the MSA-PDZ film from exposure to moisture. Owing to the synergetic effect from the TCPI/Gr/MSA-PDZ anode structure, the TCPI/Gr/MSA-PDZ-based polymer light-emitting diodes showed highly improved current and power efficiencies with maxima as high as 20.84 cd/A and 22.92 lm/W, respectively (comparable to those of indium tin oxide based PLEDs), in addition to much enhanced mechanical flexibility.

Lead halide perovskites (LHPs) are emerging as promising materials for light-emitting device applications because of the tunability of the band gap, narrow emission, solution processability, and flexibility. Typically, LHP nanocrystals (NCs) with surface ligands show high photoluminescence quantum yields because of charge-carrier confinement with higher exciton binding energy (Eb). However, the conventionally used oleylamine (OAm) ligands result in the low electrical conductivity and stability of perovskite NCs (PNCs) because of a long carbon chain without conjugation bonds and weak interaction with the surface of NCs. Here, we report the effect of bulkiness and chain length of ligand materials on the properties and stability of CsPbBr3 PNCs by replacing OAm with other suitable ligands. The effect of the bulkiness of quaternary ammonium bromide (QAB) ligands was systemically studied. The less bulky QAB ligands surrounded the surface of NCs effectively, and brought better surface passivation and less aggre...

Tin oxide (SnO2) is widely adopted as an electron transport layer in perovskite solar cells (PeSCs) because it has high electron mobility, excellent charge selective behavior owing to a large band gap of 3.76 eV, and low-temperature processibility. To achieve highly efficient SnO2-based PeSCs, it is necessary to control the oxygen vacancies in the SnO2 layer, since the electrical and optical properties vary depending on the oxidation state of Sn. This study demonstrates that the performance of PeSCs may be improved by using nitrogen-doped graphene oxide (NGO) as an oxidizing agent for SnO2. Since NGO changes the oxidation state of the Sn in SnO2 from Sn2+ to Sn4+, the oxygen vacancies in SnO2 can be reduced using NGO. Multiple devices are fabricated, and various techniques are used to assess their performance, including X-ray photoelectron spectroscopy, dark current analysis, and the dependence of the open-circuit voltage on light intensity. Compared with the average power conversion efficiency (PCE) of control devices, PeSCs with SnO2:NGO composite layers exhibit greater PCEs with less deviation. Therefore, the introduction of NGO in a SnO2 layer can be regarded as an effective method of controlling the oxidation state of SnO2 to improve the performance of PeSCs.

Organic–inorganic hybrid perovskites are emerging as promising emitting materials due to their narrow full-width at half-maximum emissions, color tunability, and high photoluminescence quantum yields (PLQYs). However, the thermal generation of free charges at room temperature results in a low radiative recombination rate and an excitation-intensity-dependent PLQY, which is associated with the trap density. Here, we report perovskite films composed of uniform nanosized single crystals (average diameter = 31.7 nm) produced by introducing bulky amine ligands and performing the growth at a lower temperature. By effectively controlling the crystal growth, we maximized the radiative bimolecular recombination yield by reducing the trap density and spatially confining the charges. Finally, highly bright and efficient green emissive perovskite light-emitting diodes that do not suffer from electroluminescence blinking were achieved with a luminance of up to 55 400 cd m–2, current efficiency of 55.2 cd A–1, and exte...

Organic–inorganic hybrid perovskites have been investigated extensively for use in perovskite-based solar cells and light-emitting diodes (LEDs) because of their excellent electrical and optical properties. Although the flexibility of perovskite LEDs has been studied through empirical methods such as cyclic bending tests, the flexibility of the perovskite layer has not been investigated systemically. Here, flexible and semitransparent perovskite LEDs are fabricated: a PEDOT:PSS anode and Ag nanowire cathode allow for flexible and semitransparent devices, while the use of a conjugated polyelectrolyte as an interfacial layer reduces the electron injection barrier between the cathode and the electron transport layer (SPW-111), resulting in enhanced device efficiency. Cyclic bending tests performed on the electrodes and in situ hole–nanoindentation tests performed on the constituent materials suggest that mechanical failure occurs in the perovskite MAPbBr3 layer during cyclic bending, leading to a decrease in...

Mechanical properties of transparent electrodes, including flexibility, are important in flexible electronics for sustaining electrical conductivity under bending with small radius of curvature. Low contact resistance of junctions in metal nanowire percolation networks is the most important factor to produce electrodes with excellent optical, electrical and mechanical performance. Here, we report the fabrication of welded silver nanowire percolation networks using large pulsed electron beam (LPEB) irradiation as a welding process of silver nanowires (AgNWs). It results in modification of electrical and mechanical properties because of the low contact resistance at welded junctions. Consequently, the flexible and transparent AgNW electrodes fabricated by LPEB irradiation showed lower sheet resistance of 12.63 Ω sq(-1) at high transmittance of 93% (at 550 nm), and superb mechanical flexibility, compared with other AgNW electrodes prepared by thermal treatement and without any treatment. Polymer light-emitting diodes (PLEDs) using AgNWs by LPEB irradiation were fabricated to confirm that the AgNW electrode by LPEB irradiation was able to become alternative to indium tin oxide (ITO) and they showed good device performance as a maximum luminous efficiency of 7.37 cd A(-1), and excellent mechanical flexibility under bending with small radius of curvature.

This study was conducted to investigate the effects of deep eutectic solvent (DES) treat-ment on BCTMP fibers and handsheets properties. DES was prepared using lactic acid and betaine (LB), and the molar ratio of these two components mixtures was controlled to 2:1 (LB 2:1) and 5:1 (LB 5:1). As results, 2% of BCTMP pulp (o.d. weight) was extracted when it was treated by LB 5:1 at 50℃ for 12 hours, stirring constantly at 120 rpm. In contrast, lignin was not extracted when BCTMP was mildly treated by the LB DES mixed with 50% of distilled water at the reacting condition of temperature 60℃ for 2 hours using water bath. These results indicate that conditioned water content and adequate reaction time are needed to achieve effective extraction of lignin. It was also found that stiffening of cellulose fiber due to the mild treatment of LB DES to BCTMP fiber leads to the increase of paper bulk without the loss of strength.Keywords: Deep eutectic solvent, LB (lactic acid and betaine), bleached chemithermome-chanical pulp, fiber properties, handsheet properties

The effects of pulp beating degree and bulky promotor concentration on the properties of handsheet including a bulk and strength have been investigated during manufacturing of low density paper (high bulk paper) with cationic fatty acid bulky promotor. It was found that paper bulk increased with increasing cationic fatty acid bulky agent concentration, while tensile strength decreased. On the other hand the opacity of handseets also increased with increasing cationic fatty acid bulky agent concentration, while brightness decreased slightly. With increasing pulp beating degree, paper bulk as well as tensile strength increased, while opacity decreased. Brightness did not show a significant difference with increasing pulp beating degree. The highest bulk and strength values were observed when 1.5% (SwBKP) and 2% (HwBKP) of bulky promotor was treated into the 450 mL CSF pulp slurry.

We demonstrate the enhanced performance of perovskite light-emitting diodes (PeLEDs) using a solution-processable MoO3 and PEDOT:PSS (PEDOT:MoO3) composite layer as the hole transport layer (HTL). The PEDOT:MoO3 composite layer presents improved hole injection through a reduction in the contact barrier between the HTL and the CH3NH3PbBr3 layer and enhanced crystallinity of the perovskite film. The optimized PeLEDs with the PEDOT:MoO3 composite film showed enhanced external quantum efficiency (EQE) and maximum luminous efficiency, compared to a PeLED using a pristine PEDOT:PSS layer.

Metal halide perovskites (MHPs) have emerged as promising materials for light‐emitting diodes owing to their narrow emission spectrum and wide range of color tunability. However, the low exciton binding energy in MHPs leads to a competition between the trap‐mediated nonradiative recombination and the bimolecular radiative recombination. Here, efficient and stable green emissive perovskite light‐emitting diodes (PeLEDs) with an external quantum efficiency of 14.6% are demonstrated through compositional, dimensional, and interfacial modulations of MHPs. The interfacial energetics and optoelectronic properties of the perovskite layer grown on a nickel oxide (NiOx) and poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate hole injection interfaces are investigated. The better interface formed between the NiOx/perovskite layers in terms of lower density of traps/defects, as well as more balanced charge carriers in the perovskite layer leading to high recombination yield of carriers are the main reasons for significantly improved device efficiency, photostability of perovskite, and operational stability of PeLEDs.

Perovskite-based optoelectronic devices have been rapidly developing in the past 5 years. Since the first report, the external quantum efficiency (EQE) of perovskite light-emitting diodes (PeLEDs) has increased rapidly through the control of morphology and structure from 0.1% to more than 11%. Here, we report the use of various conjugated polyelectrolytes (CPEs) as the hole injection layer in PeLEDs. In particular, we find that poly[2,6-(4,4-bis-potassium butanylsulfonate)-4 H-cyclopenta-[2,1- b;3,4- b']-dithiophene)] (PCPDT-K) transfers holes effectively, blocks electron transport from the perovskite to the underlying ITO layer, and reduces luminescence quenching at the perovskite/PCPDT-K interface. Our optimized PeLEDs with PCPDT-K show enhanced EQE by a factor of approximately 4 compared to control PeLEDs with PEDOT:PSS, reaching EQE values of 5.66%, and exhibit improved device stability.

Here, we report a comprehensive analysis of the electrical, optical, mechanical, and surface morphological properties of composite nanostrutures based on silver nanowires (AgNW) and PEDOT:PSS conducting polymer for the use as flexible and transparent electrodes. Compared to ITO or the single material of AgNW or PEDOT:PSS, the AgNW/PEDOT:PSS composite electrode showed high electrical conductivity with a low sheet resistance of 26.8 Ω/sq at 91% transmittance (at 550 nm), improves surface smoothness, and enhances mechanical properties assisted by an amphiphilic fluoro-surfactant. The polymeric light-emitting diodes (PLEDs) and organic solar cells (OSCs) using the AgNW/PEDOT:PSS composite electrode showed higher device performances than those with AgNW and PEDOT:PSS electrodes and excellent flexibility under bending test. These results indicates that the AgNW/PEDOT:PSS composite presented is a good candidate as next-generation transparent elelctrodes for applications into flexible optoelectronic devices.

In this study, the effects of cationic fatty acid bulky promotor on the properties of BCTMP (bleached chemithermomechnical pulp) handsheet including bulk and strength were elucidated. As results, it was observed that the bulk of BCTMP handsheet increased with the increases of the concentration of cationic fatty acid bulky agent, while mechanical properties such as tensile strength and burst strength decreased. The opacity of BCTMP handsheet also increased with the increases of the concentration of cationic fatty acid bulky agent, while brightness was almost not changed. The effectiveness of bulky agent with SwBCTMP (softwood) was higher than that with HwBCTMP (hardwood). Compared with previous research on the effect of bulky agent on BKP handsheet, the bulk increase of BCTMP handsheet was greater compared to that of BKP handsheet. However, the reduction of mechanical property in BCTMP handsheet was lower than that of BKP handsheet.

The change in the work function (WF) of ZnO with amine-based interfacial mole-cules (AIM) can be controlled by the number of amine groups. AIM with a larger amine group can induce a stronger interface dipole between the amine groups and the ZnO surface, leading to a greater reduction of the WF.

Disposable diaper has been used in order to handle urine and feces conveniently. At present the amount of disposable diaper waste increases gradually. Incineration and landfill have been the only ways to dispose of disposable diapers. However, if they are disposed by landfill, decomposition will take more than one hundred years. In addition, another way of dispose incineration has caused air pollution. Therefore, it is necessary to study recycling process for disposable diaper since plastic and wood fibers of diaper are useful materials to recycle. In this study, pulping condition of disposable diaper waste was studied in order to effectively separate the components. Recovery rates of plastic and fibers were analyzed under different pulping conditions. It was found that optimum pulping consistency was 5%, time was 60 minutes, temperature was 50°C, and cut size is 21 cm×21 cm. The recovery rate of plastic and fibers can be achieved above 70% under the optimum pulping condition.

As a part of the study on manufacture of low density paper by organic bulky agent treatment, the effects of cationic fatty acid bulky agent on physical and optical properties of handsheets were elucidated. The research on change of physical and optical properties of paper samples according to bulky agent concen-tration, pulp type, and pulp combination werecarried out. The results demonstrated that an increase of the concentration of cationic fatty acid bulky agent was proportional to an increase of the bulky properties of paper samples while tensile strength decreased. Also, the more the treated concentration of cationic fatty acid bulky agent increased, the more the ISO brightness of paper samples decreased while the opac-ity increased. The effectiveness of bulky agent with softwood bleached kraft pulp (SwBKP) was higher than that with hardwood bleached kraft pulp (HwBKP). In addition, the effectiveness with mixed pulps was higher than that with single pulp. Keywords: Bulky agent, low density paper, cationic fatty acid amine, bulky agent concentration, pulp type

Direct 3D printing technologies to produce 3D optoelectronic architectures have been explored extensively over the last several years. Although commercially available 3D printing techniques are useful for many applications, their limits in printable materials, printing resolutions, or processing temperatures are significant challenges for structural optoelectronics in achieving fully 3D‐printed devices on 3D mechanical frames. Herein, the production of active optoelectronic devices with various form factors using a hybrid 3D printing process in ambient air is reported. This hybrid 3D printing system, which combines digital light processing for printing 3D mechanical architectures and a successive electrohydrodynamic jet for directly printing transparent pixels of organic light‐emitting diodes at room temperature, can create high‐resolution, transparent displays embedded inside arbitrarily shaped, 3D architectures in air. Also, the demonstration of a 3D‐printed, eyeglass‐type display for a wireless, augmented reality system is an example of another application. These results represent substantial progress in the development of next‐generation, freeform optoelectronics., A hybrid, 3D printing system based on digital light processing and an electrohydrodynamic inkjet is developed for producing freeform optoelectronic devices in ambient air. This 3D printing system can print all components of the device as well as the mechanical frames; thus, the system can produce transparent 3D architectures with arbitrary shapes at the desired locations.

A FR-ATM interworking function that has FR and ATM interfaces, should guarantee the QoS of both frame relay and ATM networks. The IWF requires the policing mechanisms for FR and ATM respectively, and needs to map the traffic parameters each other. In this case, traffic parameter mapping and policing function are performed independently. In the aspect of FR traffic policing, this function degrades processor performance if it is worked by software, or includes additional hardware function. The best way to solve this is to integrate this function into ATM function because ATM is performed by well defined hardware already. In this paper we propose the integrated traffic control mechanism. That is, frames are segmented to cells first, and then policing mechanism is applied to the cells to guarantee the FR QoS. Therefore proper policing algorithm is essential to the integrated FR traffic mechanism. The evaluations are done with simulations in comparison of existing FR algorithms, ATM VBR and GFR policing algorithms, and the proposed algorithm.

Organic light-emitting diodes have been recently focused for flexible display and solid-state lighting applications and so much effort has been devoted to achieve highly efficient organic light-emitting diodes. Here, we improve the efficiency of inverted polymer light-emitting diodes by introducing a spontaneously formed ripple-shaped nanostructure of ZnO and applying an amine-based polar solvent treatment to the nanostructure of ZnO. The nanostructure of the ZnO layer improves the extraction of the waveguide modes inside the device structure, and a 2-ME + EA interlayer enhances the electron injection and hole blocking in addition to reducing exciton quenching between the polar-solvent-treated ZnO and the emissive layer. Therefore, our optimized inverted polymer light-emitting diodes have a luminous efficiency of 61.6 cd A(-1) and an external quantum efficiency of 17.8%, which are the highest efficiency values among polymer-based fluorescent light-emitting diodes that contain a single emissive layer.

The interfacial dipolar polarization in inverted structure polymer solar cells, which arises spontaneously from the absorption of ethanolamine end groups, such as amine and hydroxyl groups on ripple-structure zinc oxide (ZnO-R), lowers the contact barrier for electron transport and extraction and leads to enhanced electron mobility, suppression of bimolecular recombination, reduction of the contact resistance and series resistance, and remarkable enhancement of the power conversion efficiency.

We describe an off-line handwritten Korean character recognition module for real-time address reading. Our module has a two-stage recognition structure. The first recognition aims at reducing target classes for the second recognition at high-speed. We introduced a method to remove non-similar candidates with an input from the candidate set returned by the first recognizer. The optimal candidate set obtained after the operation of the removal method is used to be the target class set for the second recognition and hence should include the class membership of input without fail and a possible small number of candidates in consideration of the whole processing time. The result of experiment done with the PE92 database has proven the superiority of the removal method.

This paper describes some of research results related to the development of a character recognizer appropriate for fast handwritten Korean address reading. Our goal is to design a handwritten Korean character recognizer retaining the following three characteristics: reliable recognition scores indicating probability, high speed, and naturally acceptable cumulative recognition rates. We have adopted two statistical classifiers to satisfy the first characteristic and proposed methods coupling the two classifiers to meet the second and third ones. The superiority of the proposed combination methods has been proven through experiments done with the PE92 database.

An approach to solving the time-varying obstacle avoidance problem is pursued. The mathematical formulation of the problem is given in robot joint space (JS). The view-time concept is introduced to deal with time-varying obstacles. The view-time is the period in which a time-varying obstacle is viewed and approximated by an equivalent stationary obstacle. The equivalent stationary obstacle is the volume swept by the time-varying obstacle for the view-time. The swept volume is transformed into the JS obstacle that is the set of robot configurations causing the collision between the robot and the swept volume. In JS, the path avoiding the JS obstacle is planned, and a trajectory satisfying the constraints on robot motion planning is planned along the path. This method is applied to the collision-free motion planning of two SCARA robots, and the simulation results are given. >

This paper proposes a new motion planning method of a mobile robot avoiding moving obstacles. To avoid moving obstacles, the trajectories of the obstacles are predicted using a stochastic model of obstacle motion. The obstacle motion is modeled as a random walk process. The method plans robot motion by the unit of view-time and view-period. View-time is defined as the time instant at which the robot senses the obstacle position and velocity. View-period is defined as the time interval during which the robot performs sensing, predicting and planning for collision-free motion. From the position and velocity at a view-time, we predict the future position of the obstacle. The random walk process model of obstacle motion is used to calculate the probability density that the predicted position is reached during the view-period. From the probability density function of the predicted position, the probability that a position can be swept by the obstacle during the view-period is calculated. Then artificial potential is assigned at every position by considering the probability. The force induced by the artificial potential field repels the robot away from the probable obstacle trajectory. This method is a look ahead scheme, and effective for moving obstacle avoidance. This method is applied to collision-free motion planning for a mobile robot in a dynamic and unknown environment with several moving and stationary obstacles.

This paper proposes a unified method for moving obstacle avoidance of a robot. The method incorporates the artificial potential field (APF) concept into view-time based motion planning where the driving force is generated at every interval of the view-time. The view-time is defined as the time set from one sampling time instant to the next. The velocity and acceleration of the moving obstacle is assumed to be monitored or priorly known at each sampling time. At each sampling time, an accessible region that will be swept by the obstacle in the next view-time is predicted from the velocity, acceleration, and dynamic constraints of the obstacle. Then, an APF which exerts repulsive force on the robot is constructed around the accessible region. During the view-time, the force induced by the artificial potential field drives the robot away from the accessible obstacle trajectories in real-time. The dynamic constraints of the robot are also considered. Application of the described procedure at each successive sampling time from the initial to final location yields the collision-free trajectory for moving obstacle avoidance.

This paper proposes a new motion planning method of a mobile robot avoiding moving obstacles. We use an artificial potential field method and the view-time concept. The view-time is defined as the period between one sampling time to the next. It is assumed that the position and the velocity of obstacles are monitored at each sampling time. From the position and velocity at sampling time, we calculate the probability density of the obstacle trajectory for a view-time, based on the assumption that the obstacle motion is being modeled as a random walk process. The probability that the position can be swept by an obstacle during a view-time is calculated from the probability density function of the obstacle trajectory. Then artificial potential is assigned at every position by considering the probability of obstacle trajectory. The force induced by the artificial potential field repels the robot away from the probable obstacle trajectory. This method is a look ahead scheme and is effective for moving obstacle avoidance.

A systematic approach for encoding Korean addresses to the finest depth of sort is presented in this paper. The implementation is focused on producing the final delivery point code for various types of address recognized in an efficient manner. There are two stages in the address interpretation: 1) agreement verification between the recognized postal code and upperpart of the address; and 2) analysis of the lower part of the address which is important for the encoding. In the agreement verification procedure, the recognized postal code is used as a key to access the address dictionary and each of the retrieved addresses is compared with the words in the recognized address. As a result, the boundary between the upper part and the lower part is located. The confusion matrices are introduced to improve the performance of the process by correcting misrecognized characters. In the procedure of interpreting the lower address part, a delivery point code is derived using the house number and/or the building name. Several rules for the interpretation have been developed based on the analysis of real addresses collected. Experiments have been performed to evaluate the proposed approach using addresses collected from two metropolitan cities in Korea.

We present flexible polymer light-emitting diodes (FPLEDs) using graphene oxide-modified single-walled carbon nanotube (GO-SWCNT) films as an anode on polyethylene terephthalate (PET) substrates. The electrode of GO-SWCNTs used in this study shows quite a low sheet resistance of ∼75 Ω per square at 65% (at 550 nm) optical transparency with resistance to bending fatigue. The small-sized GO nanosheets onto the SWCNT network films are significantly effective in reducing the sheet resistance and the surface porosity of the SWCNT network films without sacrificing the transmittance. Moreover, the top layer of the large-sized GO nanosheets are crucial for high device efficiency to reduce the roughness of the SWCNT surface and enhance the wettability with PEDOT:PSS. The optimized FPLED using a GO-SWCNT electrode shows a maximum luminous efficiency of 5.0 cd A−1 (at 9.2 V), power efficiency of 2.4 lm W−1 (at 5.6 V), external quantum efficiency 1.9% (at 9.0 V) and turn-on voltage (2.0 V), which is comparable to conventional PLEDs using an indium-tin-oxide (ITO) electrode (a maximum luminous efficiency of 6.2 cd A−1 (at 9.4 V), power efficiency of 2.6 lm W−1 (at 5.8 V), external quantum efficiency 2.3% (at 9.0 V) and turn-on voltage (2.0 V)). This result confirms that a GO-SWCNT electrode can be efficiently used to replace ITO for flexible optoelectronic devices.