Plasma-treated Indium Tin Oxide Research Articles

Electrical Stimulation of Human Adipose-Derived Mesenchymal Stem Cells on O2 Plasma-Treated ITO Glass Promotes Osteogenic Differentiation.

Electrical signals represent an essential form of cellular communication. For decades, electrical stimulation has been used effectively in clinical practice to enhance bone healing. However, the detailed mechanisms between electrical stimulation and bone healing are not well understood. In addition, there have been many difficulties in setting up a stable and efficient electrical stimulation system within the in vitro environment. Therefore, various conductive materials and electrical stimulation methods have been tested to establish an effective electrical stimulation system. Through these systems, many studies have been conducted on the effects of electrical stimulation on bone healing and osteogenic differentiation. However, previous studies were limited by the use of opaque conductive materials that obscure the cells; fluorescent observations and staining are known to be two of the critical methods to confirm the states of the cells. Indium tin oxide (ITO) glass is known to have excellent transparency and conductivity, but it is challenging to cultivate cells due to low cell adhesion characteristics. Therefore, we used O2 plasma treatment to increase the hydrophilicity and wettability of ITO glass. This enhanced cell affinity to the glass, providing a stable surface for the cells to attach. Then, electrical stimulation was applied with an amplitude range of 10 to 200 µA at a frequency of 10 Hz. Our results demonstrated that the osteogenic differentiation efficiency was maximized under the amplitude conditions of 10 µA and 50 µA. Accordingly, the results of our study suggest the development of an excellent platform in the field of biological research as a good tool to elucidate various mechanisms of cell bioactivity under electrical conditions.

Effect on the reduction of the barrier height in rear-emitter silicon heterojunction solar cells using Ar plasma-treated ITO film

In this study, we investigated the effect of plasma treatment on an indium tin oxide (ITO) film under an ambient Ar atmosphere. The sheet resistance of the plasma-treated ITO film at 250 W (37.6 Ω/sq) was higher than that of the as-deposited ITO film (34 Ω/sq). Plasma treatment was found to decrease the ITO grain size to 21.81 nm, in comparison with the as-deposited ITO (25.49 nm), which resulted in a decrease in the Hall mobility. The work function of the Ar-plasma-treated ITO (WFITO=4.17 eV) was lower than that of the as-deposited ITO film (WFITO = 5.13 eV). This lower work function was attributed to vacancies that formed in the indium and oxygen vacancies in the bonding structure. Rear-emitter silicon heterojunction (SHJ) solar cells fabricated using the plasma-treated ITO film exhibited an open circuit voltage (VOC) of 734 mV, compared to SHJ cells fabricated using the as-deposited ITO film, which showed a VOC of 704 mV. The increase in VOC could be explained by the decrease in the work function, which is related to the reduction in the barrier height between the ITO and a-Si:H (n) of the rear-emitter SHJ solar cells. Furthermore, the performance of the plasma-treated ITO film was verified, with the front surface field layers, using an AFORS-HET simulation. The current density (JSC) and VOC increased to 39.44 mA/cm2 and 736.8 mV, respectively, while maintaining a WFITO of 3.8 eV. Meanwhile, the efficiency was 22.9% at VOC = 721.5 mV and JSC = 38.55 mA/cm2 for WFITO = 4.4 eV. However, an overall enhancement of 23.75% in the cell efficiency was achieved owing to the low work function value of the ITO film. Ar plasma treatment can be used in transparent conducting oxide applications to improve cell efficiency by controlling the barrier height.

Tuning the ITO work function by capacitively coupled plasma and its application in inverted organic solar cells

In this paper, we investigated the performance of inverted organic solar cells (OSCs) with plasma-treated indium tin oxide (ITO) as the cathode for omitting an electron transport layer. The Ar plasma was produced by capcitively coupled plasma setup under 20Pa chamber pressure. For the device with the structure of plasma-treated ITO/P3HT:PCBM/MoO3/Ag, a power conversion efficiency (PCE) of 3.22% was achieved, whereas PCE of 1.13% was recorded from the device fabricated with the pristine ITO. The photovoltaic performance was found to be dependent on the applied power of plasma. After analyzing by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), we concluded that the chemical component variation of ITOs surface resulted in the decrease of ITO work function, which meant that the ITO Fermi level became shallow relative to the vacuum level. The low work function of ITO should be responsible for the improvement of inverted OSCs because of the better energy level alignment between ITO and the photoactive layer.

Influence of plasma treatment on Indium Tin Oxide electrodes

Organic Schottky diodes (OSDs) with various plasma treated Indium Tin Oxide (ITO) as anodic electrode are prepared and tested to investigate the effect of plasma treatment on their performance. Oxygen plasma treated ITO (O-ITO), nitrogen plasma treated ITO (N-ITO) and plasma untreated ITO (U-ITO) are used. The current density–voltage analysis and electrochemical impedance spectroscopic analysis are utilized in the study. The frequency-dependent response is interpreted in terms of an equivalent-circuit model consisting of three resistors, two capacitors, and one inductor. Device parameters are extracted by fitting equivalent circuit with obtained impedance data. Capacitance–voltage (C–V), and ac conductance–voltage (G(ω)–V) features of the OSDs are analyzed in the frequency of 1kHz. It has been concluded that the OSDs fabricated using N-ITO showed lower impedance and higher capacitance than other devices.

Work function changes of plasma treated indium tin oxide

The work function (WF) changes of indium tin oxide (ITO) treated by O2 or Cl2 plasma were invested. The WF firstly decreases in an exponential way for 2–6h and subsequently in a linear way for days in air after plasma treatment. X-ray photoelectron spectroscopy (XPS) shows the dipole layer formed by O–In and O–O bonds in the ITO surface treated by O2 plasma increases the WF. Exposed in vacuum, the O–O bonds tend to break and the reactive O species reduce in the oxidized ITO surface, accounting for the exponential decrease of WF. The environment preserving the chlorinated or oxidized ITO is important to slow down the decrease of WF. The mechanism for WF changes of plasma treated ITO is significant to investigate the properties of organic optoelectronic devices.

Low-cost electrochemical treatment of indium tin oxide anodes for high-efficiency organic light-emitting diodes

We demonstrate a simple low-cost approach as an alternative to conventional O2 plasma treatment to modify the surface of indium tin oxide (ITO) anodes for use in organic light-emitting diodes. ITO is functionalized with F− ions by electrochemical treatment in dilute hydrofluoric acid. An electrode with a work function of 5.2 eV is achieved following fluorination. Using this electrode, a maximum external quantum efficiency of 26.0% (91 cd/A, 102 lm/W) is obtained, which is 12% higher than that of a device using the O2 plasma-treated ITO. Fluorination also increases the transparency in the near-infrared region.

P.114: Cl2 Plasma Treated Indium Tin Oxide Electrodes with High Work Function for Organic Light‐Emitting Diodes

AbstractThe ITO is used transparent electrode that has low work function of ∼4.7 eV. In this reason OLEDs needs to match the energy levels between the ITO and organic materials also needs additional materials. In this study, without any additional materials, we demonstrate higher efficiency device than reference devices using Cl2 plasma treated ITO with a work function of ∼5.9eV.

Solution-processed-MoO3 hole extraction layer on oxygen plasma-treated indium tin oxide in organic photovoltaics

Effects of oxygen plasma (O2 plasma) treatment of ITO on the characteristics of solution-processed molybdenum oxide (MoO3) hole extraction layer in bulk hetero-junction organic photovoltaics (OPVs) are studied. The chemical composition of O2 plasma-treated ITO was determined using monochromatic X-ray photoelectron spectroscopy (XPS). The valence band energies were investigated by ultraviolet photoemission spectroscopy (UPS) measurements. XPS and UPS measurements reveal that O2 plasma treatment of bare ITO film was found to incorporate the polar surface species such as (O2)2−, resulting in an increase of both workfunction from 4.62 to 5.05eV and polar surface energy from 27 to 38mN/m. The high work function results in efficient hole transport at the ITO/MoO3 interfaces. The highly polar surface is readily available for uniform coating of MoO3 on ITO. Electrical conductivity of oxidized ITO changes four orders of magnitude from 2.4×10–2 to 4.08×102S/cm, depending on O2 plasma pressure conditions. Thus, the ITO/MoO3 interface dominates the series resistance of OPVs fabricated with poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The presence of (O2)2− states in the ITO/MoO3 interface in OPVs is suggested to play a significant role in controlling the device lifetime as well as the efficiency of OPV.

Enhanced Power Efficiency of Organic Light-Emitting Diodes using Pentacene on $\hbox{CF}_{4}$-Plasma-Treated Indium Tin Oxide Anodes

In this letter, we demonstrate high-performance organic light-emitting diodes (OLEDs) by matching various hole injection-transport layers (HITLs) with plasma surface treatments. The OLED device with pentacene HITL on CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -plasma-treated indium tin oxide showed the highest performance due to relatively improved hole injection and the high-hole-mobility characteristics of the pentacene. Using a high-electron-mobility material as an electron transport layer to improve the carrier balance of electrons and holes, the electroluminescent efficiency was further improved. These methods are simple and promising for the enhancement of OLED performances. These findings will be applicable to mobile displays that feature low electric power consumption.

Efficient and reliable green organic light-emitting diodes with Cl2 plasma-etched indium tin oxide anode

The effects of brief etching with Cl2-based inductively coupled plasma (ICP) on the surface chemistry and properties of indium-tin-oxide (ITO) were investigated. Due to the low volatility of InClx, Cl2, and Cl2/BCl3 ICP etching created stable In-Cl polar bonds at the ITO surfaces, raising its work function by up to 1.0 eV. Green phosphorescent organic light-emitting diodes (OLEDs) built on ICP-etched ITO/glass substrates exhibited a brightness of 1.4 × 104 cd/m2 and a current efficiency of 70 cd/A at 20 mA/cm2, which were 40% higher than those of similar OLEDs with an O2 plasma-treated ITO anode. The OLEDs with plasma chlorinated ITO also showed better stability and reliability. These results suggest that brief chlorine plasma etching can result in stable chlorinated ITO surfaces with a high work function, leading to more balanced charge injection and performance enhancement of OLEDs.

Performance enhancement of organic light-emitting diodes by chlorine plasma treatment of indium tin oxide

The characteristics of green phosphorescent organic light-emitting diodes (OLEDs) fabricated on ITO/glass substrates pretreated with low-energy O2 and Cl2 plasma were compared. At 20 mA/cm2, the OLEDs with O2 and Cl2 plasma-treated indium tin oxide (ITO) had voltages of 9.6 and 7.6 eV, and brightness of 9580 and 12380 cd/m2, respectively. At ∼104 cd/m2, the latter had a 30% higher external quantum efficiency and a 74% higher power efficiency. Photoelectron spectroscopies revealed that Cl2 plasma treatment created stable In-Cl bonds and raised the work function of ITO by up to 0.9 eV. These results suggest that the better energy level alignment at the chlorinated ITO/organic interface enhances hole injection, leading to more efficient and more reliable operation of the OLEDs. The developed plasma chlorination process is very effective for surface modification of ITO and compatible with the fabrication of various organic electronics.

불소계열 플라즈마 처리를 통한 수직형 UV LED용 ITO/Al 기반 반사전극의 전기적/광학적 특성 최적화

We optimize electrical and optical properties of thermal and SF6 plasma treated indium tin oxide (ITO)/Al based reflector for high-power ultraviolet (UV) light-emitting diodes (LEDs). After thermal and <TEX>$SF_6$</TEX> plasma treatments of ITO/Al reflector, the specific contact resistance decreased from <TEX>$1.04{\times}10^{-3}\;{\Omega}{\cdot}cm^2$</TEX> to <TEX>$9.21{\times}10^{-4}\;{\Omega}{\cdot}cm^2$</TEX>, while the reflectance increased from 58% to 70% at the 365 nm wavelength. The low resistance and high reflectance of ITO/Al reflector are attributed to the reduced Schottky barrier height (SBH) between the ITO and AlGaN by large electronegativity of fluorine species and reduced interface roughness between the ITO and Al, respectively.

Reduced hole injection barrier for achieving ultralow voltage polymer space-charge-limited transistor with a high on/off current ratio

Vertical polymer space-charge limited transistor (SCLT) operated with an ultralow voltage is demonstrated. The influence of aging effect of the oxygen plasma treated indium tin oxide electrode on the hole injection barrier and on the transistor characteristics is investigated. By reducing the hole injection barrier, the on/off ratio as high as 104 is obtained at a collector to emitter voltage as low as −0.84 V. The low operation voltage is crucial to the development of low-power large-area polymer transistor array. Inverter characteristics are also demonstrated by connecting a SCLT with a load resistor.

In Situ Analysis of Hole Injection Barrier of Molybdenum-Oxide-Coated Anode with Organic Materials Using Synchrotron Radiation Photoemission Spectroscopy

We report the enhancement of the electroluminescent property of organic light-emitting diodes (OLEDs) using as a hole injection layer between indium tin oxide (ITO) anodes and -bis[-(1-naphthyl)--phenyl-amino]biphenyl . The operation voltage for of OLEDs with a 10 Å thick layer decreased from 24.5 to 14.7 V, and the luminescence value at increased from 1280 to . was deposited in situ on -plasma-treated ITO anodes and anodes coated with an -plasma-treated layer , and their interface dipole energies were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra after the deposition of on anodes revealed that the work function of is 0.55 eV higher than that of . The corresponding interface dipole energies were −0.20 eV for and −0.50 eV for . The hole injection barrier at the interface was reduced from 1.15 to 0.85 eV by the deposition of , resulting in an enhancement of the electroluminescence property of OLEDs.

Characterization of CF4 Plasma-Treated Indium–Tin-Oxide Surfaces Used in Organic Light-Emitting Diodes by X-ray Photoemission Spectroscopy

The CF4 plasma treatment of indium–tin-oxide (ITO) greatly improves the performance of organic light-emitting diodes (OLEDs). The effects of plasma treatment on the chemical composition change and device performance were investigated by X-ray photoemission spectroscopy (XPS). The present results suggest that fluorine directly bonded to indium or tin on the ITO surface and markedly enhanced device performance.

Impedance Spectroscopy Analysis of Organic Light-Emitting Diodes Fabricated on Plasma-Treated Indium-Tin-Oxide surfaces

In this work, impedance spectroscopy analysis was used to study the eects of plasma treatment on the surface of indium-tin oxide (ITO) anodes using CF4, O2 and Ar gases and to model an equivalent circuit for organic light-emitting diodes (OLEDs). The devices with an ITO/TPD/Alq3/LiF/Al structure could be modeled as a simple combination of resistors and capacitors. For modifications of the ITO surface, the samples were treated in an inductively-coupled tubular reactor system. The OLEDs fabricated on plasma-treated ITO anodes showed a lower impedance and a higher capacitance. The changes in the impedance and the capacitance were attributed to removal of contaminants and to changes in the work function of ITO. The impedance spectroscopy analysis showed that the devices with plasma-treated ITO anodes had dierent values of the contact resistance (RC), the parallel resistance (RP) and the parallel capacitance (CP).

Room temperature crystallization of indium tin oxide films on glass and polyethylene terephthalate substrates using rf plasma

The crystallization of amorphous indium tin oxide (ITO) films was achieved by rf (13.56MHz) plasma treatment. Although the films were crystallized after 2min, the sample temperature was lower than 90°C without compulsory cooling even after 10min of treatment and polyethylene terephthalate (PET) substrates had no damage. Plasma-crystallized sputtered ITO films have a bixbite structure and the resistivity reached to 1.6×10−4Ω∙cm. ITO thin films have almost the same resistivity in both cases of PET and glass substrates used and plasma-treated PET ITO films have a bit higher resistivity than that of glass ITO films, while mass spectroscopy measurements indicated that ITO films deposited on PET substrates are expected to include no apparent gas species ejected from PET substrate. It was found that the plasma gas pressure is the key parameter for the effective crystallization and the appropriate gas pressure depends on the plasma gas species.

Properties of Polymer Light Emitting Diodes with Blue Color on ITO/Glass Substrates

Polymer light emitting diodes (PLEDs) with ITO/PEDOT:PSS/PVK/PFO-poss/LiF/Al structure were prepared by spin coating method on the plasma-treated ITO(indium tin oxide)/glass substrates. PVK(N-vinylcabozole) and PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] polymers were used as hole injection and transport materials. As blue light emitting material, PFO-poss(poly(9,9-dioctylfluorence) polymer was used. The dependence of the plasma treatment of ITO films on the optical and electrical properties of the PLEDs was investigated. The sheet resistance of ITO films increased slightly with increasing the plasma intensity from 20W to 300W in RF power. In contrast, the surface roughness was improved as the plasma intensity increased. The maximum current density and luminance were about 20 mA/cm2 and 250 cd/m2 at 9 V for the PLED sample coated on ITO/glass substrate with plasma treatment of 100W for 30s under 40 mtorr O2 pressure. The maximum emission spectrum of the PLEDs was 441 nm showing blue color.

Plasma treatment of ITO surfaces to improve luminescence characteristics of organic light-emitting devices with dopants

Indium-tin-oxide (ITO) surfaces were treated with O 2 and H 2 plasmas. The contact angle of water, X-ray photoelectron spectroscopy (XPS) spectra, and luminescence characteristics of organic light-emitting devices (OLEDs) fabricated on plasma-treated ITO surfaces using poly( N-vinylcarbazole) (PVK) films doped with 5,6,11,12-tetraphenylnaphthacene (rubrene) or Nile Red were investigated. Using O 2 plasma treatment, the contact angle was reduced from 35° to 13°. The luminance of OLEDs with rubrene was significantly improved. The luminous color of an OLED inserted poly (3,4-ethylenedioxythiophene)-polystyrene sulphonic acid (PEDOT-PSS) layer between Nile Red-doped PVK film and O 2-plasma-treated ITO surface turned white as the applied voltage increased.

Enhanced performance of the OLED with plasma treated ITO and plasma polymerized thiophene buffer layer

In this work, indium-tin-oxide (ITO) electrode in organic light emitting device (OLED) was modified by using an O2 plasma treatment and plasma polymerized thiophene buffer layers were inserted between ITO (anode) and organic layer in order to improve the hole injection efficiency. Furthermore, electron injection to cathode (Al) in the test OLED seemed to be improved due to introduction of quantum well in the cathode. The plasma-polymerized thiophene buffer layer on the O2 plasma-treated transparent ITO electrode seemed to result in formation of a stable interface and consequently, reduction the hole mobility, which in turn caused enhanced recombination of hole and electron in the emitting layer. Compared with the test device without buffer layer, the turn-on voltage of the test device with the buffer layer was lowered by 1.0 V.