Showing papers on "Indium tin oxide published in 2015"

Single‐Layer Light‐Emitting Diodes Using Organometal Halide Perovskite/Poly(ethylene oxide) Composite Thin Films

Abstract: Organometal halide perovskite and poly(ethylene oxide) composite thin films are studied. Single-layer light-emitting diodes using the composite thin film sandwiched between indium tin oxide and indium-gallium eutectic alloy exhibit a low turn-on voltage and high brightness because of the ionic conductivity of the composite film and the formation of a p-i-n homojunction.

Upscaling of Perovskite Solar Cells: Fully Ambient Roll Processing of Flexible Perovskite Solar Cells with Printed Back Electrodes

Abstract: A scaling effort on perovskite solar cells is presented where the device manufacture is progressed onto flexible substrates using scalable techniques such as slot-die roll coating under ambient conditions. The printing of the back electrode using both carbon and silver is essential to the scaling effort. Both normal and inverted device geometries are explored and it is found that the formation of the correct morphology for the perovskite layer depends heavily on the surface upon which it is coated and this has significant implications for manufacture. The time it takes to form the desired layer morphology falls in the range of 5–45 min depending on the perovskite precursor, where the former timescale is compatible with mass production and the latter is best suited for laboratory work. A significant loss in solar cell performance of around 50% is found when progressing to using a fully scalable fabrication process, which is comparable to what is observed for other printable solar cell technologies such as polymer solar cells. The power conversion efficiency (PCE) for devices processed using spin coating on indium tin oxide (ITO)-glass with evaporated back electrode yields a PCE of 9.4%. The same device type and active area realized using slot-die coating on flexible ITO-polyethyleneterphthalate (PET) with a printed back electrode gives a PCE of 4.9%.

Ultrasmooth, extremely deformable and shape recoverable Ag nanowire embedded transparent electrode

Abstract: Transparent electrodes have been widely used in electronic devices such as solar cells, displays, and touch screens Highly flexible transparent electrodes are especially desired for the development of next generation flexible electronic devices Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices Therefore, the need for new transparent conductive materials with superior mechanical properties is clear and urgent Ag nanowire (AgNW) has been attracting increasing attention because of its effective combination of electrical and optical properties However, it still suffers from several drawbacks, including large surface roughness, instability against oxidation and moisture, and poor adhesion to substrates These issues need to be addressed before wide spread use of metallic NW as transparent electrodes can be realized In this study, we demonstrated the fabrication of a flexible transparent electrode with superior mechanical, electrical and optical properties by embedding a AgNW film into a transparent polymer matrix This technique can produce electrodes with an ultrasmooth and extremely deformable transparent electrode that have sheet resistance and transmittance comparable to those of an ITO electrode

Copper nanowire-graphene core-shell nanostructure for highly stable transparent conducting electrodes.

Abstract: A copper nanowire–graphene (CuNW-G) core–shell nanostructure was successfully synthesized using a low-temperature plasma-enhanced chemical vapor deposition process at temperatures as low as 400 °C for the first time. The CuNW-G core–shell nanostructure was systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy measurements. A transparent conducting electrode (TCE) based on the CuNW-G core–shell nanostructure exhibited excellent optical and electrical properties compared to a conventional indium tin oxide TCE. Moreover, it showed remarkable thermal oxidation and chemical stability because of the tight encapsulation of the CuNW with gas-impermeable graphene shells. The potential suitability of CuNW-G TCE was demonstrated by fabricating bulk heterojunction polymer solar cells. We anticipate that the CuNW-G core–shell nanostructure can be used as an alternative to conventional TCE materials for emerging opt...

Transparent Conductive Oxide-Free Perovskite Solar Cells with PEDOT:PSS as Transparent Electrode

Abstract: Perovskite solar cells (PSCs) have been attracting considerable attention because of their low fabrication cost and impressive energy conversion efficiency. Most PSCs are built on transparent conductive oxides (TCOs) such as fluorine-doped tin oxide (FTO) or indium tin oxide (ITO), which are costly and rigid. Therefore, it is significant to explore alternative materials as the transparent electrode of PSCs. In this study, highly conductive and highly transparent poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) films were investigated as the transparent electrode of both rigid and flexible PSCs. The conductivity of PEDOT:PSS films on rigid glass or flexible poly(ethylene terephthalate) (PET) substrate is significantly enhanced through a treatment with methanesulfonic acid (MSA). The optimal power conversion efficiency (PCE) is close to 11% for the rigid PSCs with an MSA-treated PEDOT:PSS film as the transparent electrode on glass, and it is more than 8% for the flexible PSCs with a MSA-tre...

Electrochromic bis(terpyridine)metal complex nanosheets.

Abstract: A series of electrochromic metal complex nanosheets comprising 1,3,5-tris(4-(2,2′:6′,2″-terpyridyl)phenyl)benzene or 1,3,5-tris((2,2′:6′,2″-terpyridyl)ethynyl)benzene and Fe2+ or Co2+ was synthesized. The preparation of multilayered nanosheets was achieved by liquid/liquid interfacial synthesis using an organic ligand solution and an aqueous metal–ion solution. The resultant nanosheet had a flat, smooth morphology and was several hundreds of nanometers thick. Upon its deposition on an indium tin oxide (ITO) electrode, the nanosheet underwent a reversible and robust redox reaction (Fe3+/Fe2+ or Co2+/Co+) accompanied by a distinctive color change. Electrochromism was achieved in a solidified device composed of the nanosheet, a pair of ITO electrodes, and a polymer-supported electrolyte. The combination of Fe2+ and Co2+ nanosheets in one device—deposited on each ITO electrode—demonstrated dual-electrochromic behavior.

Enhanced third-harmonic generation in Si-compatible epsilon-near-zero indium tin oxide nanolayers.

Abstract: We experimentally demonstrate enhanced third-harmonic generation from indium tin oxide nanolayers at telecommunication wavelengths with an efficiency that is approximately 600 times larger than crystalline silicon (Si). The increased optical nonlinearity of the fabricated nanolayers is driven by their epsilon-near-zero response, which can be tailored on-demand in the near-infrared region. The present material platform is obtained without any specialized nanofabrication process and is fully compatible with the standard Si-planar technology. The proposed approach can lead to largely scalable and highly integrated optical nonlinearities in Si-integrated devices for information processing and optical sensing applications.

Indium-Tin-Oxide for High-performance Electro-optic Modulation

Abstract: Abstract: Advances in opto-electronics are often led by discovery and development of materials featuring unique properties. Recently, the material class of transparent conductive oxides (TCO) has attracted attention for active photonic devices on-chip. In particular, indium tin oxide (ITO) is found to have refractive index changes on the order of unity. This property makes it possible to achieve electrooptic modulation of sub-wavelength device scales, when thin ITO films are interfaced with optical light confinement techniques such as found in plasmonics; optical modes are compressed to nanometer scale to create strong light-matter interactions. Here we review efforts towards utilizing this novel material for high performance and ultra-compact modulation. While high performance metrics are achieved experimentally, there are open questions pertaining to the permittivity modulation mechanism of ITO. Finally, we review a variety of optical and electrical properties of ITO for different processing conditions, and show that ITO-based plasmonic electro-optic modulators have the potential to significantly outperform diffractionlimited devices.

Single-Walled Carbon Nanotube Film as Electrode in Indium-Free Planar Heterojunction Perovskite Solar Cells: Investigation of Electron-Blocking Layers and Dopants

Abstract: In this work, we fabricated indium-free perovskite solar cells (SCs) using direct- and dry-transferred aerosol single-walled carbon nanotubes (SWNTs). We investigated diverse methodologies to solve SWNTs’ hydrophobicity and doping issues in SC devices. These include changing wettability of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), MoO3 thermal doping, and HNO3(aq) doping with various dilutions from 15 to 70 v/v% to minimize its instability and toxic nature. We discovered that isopropanol (IPA) modified PEDOT:PSS works better than surfactant modified PEDOT:PSS as an electron-blocking layer on SWNTs in perovskite SCs due to superior wettability, whereas MoO3 is not compatible owing to energy level mismatching. Diluted HNO3 (35 v/v%)-doped SWNT-based device produced the highest PCE of 6.32% among SWNT-based perovskite SCs, which is 70% of an indium tin oxide (ITO)-based device (9.05%). Its flexible application showed a PCE of 5.38% on polyethylene terephthalate (PET) substrate.

Optimization of silver nanowire-based transparent electrodes: effects of density, size and thermal annealing

Abstract: Silver nanowire (AgNW) networks are efficient as flexible transparent electrodes, and are cheaper to fabricate than ITO (Indium Tin Oxide). Hence they are a serious competitor as an alternative to ITO in many applications such as solar cells, OLEDs, transparent heaters. Electrical and optical properties of AgNW networks deposited on glass are investigated in this study and an efficient method to optimize them is proposed. This paper relates network density, nanowire dimensions and thermal annealing directly to the physical properties of the nanowire networksusing original physical models. A fair agreement is found between experimental data and the proposed models. Moreover thermal stability of the nanowires is a key issue in thermal optimization of such networks and needs to be studied. In this work the impact of these four parameters on the networks physical properties are thoroughly investigated via in situ measurements and modelling, such a method being also applicable to other metallic nanowire networks. We demonstrate that this approach enables the optimization of both optical and electrical properties through modification of the junction resistance by thermal annealing, and a suitable choice of nanowire dimensions and network density. This work reports excellent optical and electrical properties of electrodes fabricated from AgNW networks with a transmittance T = 89.2% (at 550 nm) and a sheet resistance of Rs = 2.9 Ω □−1, leading to the highest reported figure of merit.

Thermally Stable Silver Nanowire–Polyimide Transparent Electrode Based on Atomic Layer Deposition of Zinc Oxide on Silver Nanowires

Abstract: The performance of a flexible transparent conductive electrode with extremely smooth topography capable of withstanding thermal processing at 300 °C for at least 6 h with little change in sheet resistance and optical clarity is reported. In depth investigation is performed on atomic layer deposition (ALD) deposited ZnO on Ag nanowires (NWs) with regard to thermal and atmospheric corrosion stability. The ZnO coated nanowire networks are embedded within the surface of a polyimide matrix, and the <2 nm roughness freestanding ­electrode is used to fabricate a white polymer light emitting diode (PLED). PLEDs obtained using the ZnO-AgNW-polyimide substrate exhibit comparable performance to indium tin oxide (ITO)/glass based devices, verifying its efficacy for use in optoelectronic devices requiring high processing temperatures.

Interfacial electronic structure at the CH3NH3PbI3/MoOx interface

Abstract: Interfacial electronic properties of the CH3NH3PbI3 (MAPbI3)/MoOx interface are investigated using ultraviolet photoemission spectroscopy and X-ray photoemission spectroscopy. It is found that the pristine MAPbI3 film coated onto the substrate of poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate)/indium tin oxide by two-step method behaves as an n-type semiconductor, with a band gap of ∼1.7 eV and a valence band edge of 1.40 eV below the Fermi energy (EF). With the MoOx deposition of 64 A upon MAPbI3, the energy levels of MAPbI3 shift toward higher binding energy by 0.25 eV due to electron transfer from MAPbI3 to MoOx. Its conduction band edge is observed to almost pin to the EF, indicating a significant enhancement of conductivity. Meanwhile, the energy levels of MoOx shift toward lower binding energy by ∼0.30 eV, and an interface dipole of 2.13 eV is observed at the interface of MAPbI3/MoOx. Most importantly, the chemical reaction taking place at this interface results in unfavorable interface ene...

Recycling indium from waste LCDs: A review

Abstract: As one of the most widely used scarce metals located at the column of IIIA in the periodic table, indium has drawn more and more attention due to its semiconductor and optoelectronic performance While the reduction of indium minerals, as one of secondary resources, the amount of waste liquid crystal display (LCD) has been accumulated considerably Indium tin oxide (ITO) film which is the main functional fraction of LCD has consumed more than 70% of the indium production worldwide Therefore, it is necessary to recycle indium from waste LCDs Some researches have been done for proper treatment to recycle indium from waste LCD which is a primary part of waste electric and electronic equipment (WEEE) In this paper, the main characteristics of indium and the waste management status of end-of-life LCDs are introduced And we mainly focus on the highly developed single recycling and reusing techniques In addition, several combined recycling processes are evaluated Furthermore, on the foundation of techniques and processes mentioned above, the promising related single techniques and the improvements on whole treatment process of waste LCDs are suggested

Photoluminescence of monovalent indium centres in phosphate glass

Abstract: Valence control of polyvalent cations is important for functionalization of various kinds of materials. Indium oxides have been used in various applications, such as indium tin oxide in transparent electrical conduction films. However, although metastable In+ (5 s2 configuration) species exhibit photoluminescence (PL), they have attracted little attention. Valence control of In+ cations in these materials will be important for further functionalization. Here, we describe In+ species using PL and X-ray absorption fine structure (XAFS) analysis. Three absorption bands in the UV region are attributed to the In+ centre: two weak forbidden bands (1S0 → 3P1, 1S0 → 3P2) and a strong allowed band (1S0 → 1P1). The strongest PL excitation band cannot be attributed to the conventional allowed transition to the singlet excited state. Emission decay of the order of microseconds suggests that radiative relaxation occurs from the triplet excitation state. The XAFS analysis suggests that these In+ species have shorter In–O distances with lower coordination numbers than in In2O3. These results clearly demonstrate that In+ exists in a metastable amorphous network, which is the origin of the observed luminescent properties.

Inverted Layer‐By‐Layer Fabrication of an Ultraflexible and Transparent Ag Nanowire/Conductive Polymer Composite Electrode for Use in High‐Performance Organic Solar Cells

Abstract: A highly flexible and transparent conductive electrode based on consecutively stacked layers of conductive polymer (CP) and silver nanowires (AgNWs) fully embedded in a colorless polyimide (cPI) is achieved by utilizing an inverted layer-by-layer processing method. This CP-AgNW composite electrode exhibits a high transparency of >92% at wavelengths of 450–700 nm and a low resistivity of 7.7 Ω ◻−1, while its ultrasmooth surface provides a large contact area for conductive pathways. Furthermore, it demonstrates an unprecedentedly high flexibility and good mechanical durability during both outward and inward bending to a radius of 40 μm. Subsequent application of this composite electrode in organic solar cells achieves power conversion efficiencies as high as 7.42%, which represents a significant improvement over simply embedding AgNWs in cPI. This is attributed to a reduction in bimolecular recombination and an increased charge collection efficiency, resulting in performance comparable to that of indium tin oxide-based devices. More importantly, the high mechanical stability means that only a very slight reduction in efficiency is observed with bending (<5%) to a radius of 40 μm. This newly developed composite electrode is therefore expected to be directly applicable to a wide range of high-performance, low-cost flexible electronic devices.

Comparative Study of Second-Harmonic Generation from Epsilon-Near-Zero Indium Tin Oxide and Titanium Nitride Nanolayers Excited in the Near-Infrared Spectral Range

Abstract: We perform a comparative study of second-harmonic generation (SHG) from indium tin oxide (ITO) and from titanium nitride (TiN) nanolayers excited in the near-infrared spectrum. Both materials are compatible with Si technology and are candidate platforms for integrated nonlinear optics. In this work, we fabricate ITO samples with an e-near-zero (ENZ) condition, which can be continuously tailored in the 1150–1670 nm spectral range, and TiN samples with a metallic behavior in the same spectral range. For the ITO nanolayers, we observe tunability and enhancement of the SHG intensity when the samples are excited at their respective ENZ condition, in agreement with the electromagnetic modeling and analogous to its third-harmonic generation studied earlier. On the other hand, we show that the SHG efficiency of TiN nanolayers is lower by a factor of 50. We determine experimentally that the dominant component of the second-order susceptibility for our best ITO nanolayer is χzzz(2ω) = 0.18 pm V–1, and we theoretica...

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

Abstract: We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10−6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

An Ag-grid/graphene hybrid structure for large-scale, transparent, flexible heaters.

Abstract: Recently, carbon materials such as carbon nanotubes and graphene have been proposed as alternatives to indium tin oxide (ITO) for fabricating transparent conducting materials. However, obtaining low sheet resistance and high transmittance of these carbon materials has been challenging due to the intrinsic properties of the materials. In this paper, we introduce highly transparent and flexible conductive films based on a hybrid structure of graphene and an Ag-grid. Electrohydrodynamic (EHD) jet printing was used to produce a micro-scale grid consisting of Ag lines less than 10 μm wide. We were able to directly write the Ag-grid on a large-area graphene/flexible substrate due to the high conductivity of graphene. The hybrid electrode could be fabricated using hot pressing transfer and EHD jet printing in a non-vacuum, maskless, and low-temperature environment. The hybrid electrode offers an effective and simple route for achieving a sheet resistance as low as ∼4 Ω per square with ∼78% optical transmittance. Finally, we demonstrate that transparent flexible heaters based on the hybrid conductive films could be used in a vehicle or a smart window system.

Fully indium-free flexible Ag nanowires/ZnO:F composite transparent conductive electrodes with high haze

Abstract: Solution-processed metal nanowires (NWs) and Earth-abundant doped ZnO have been proposed to replace the most widely used indium tin oxide (ITO) transparent and conductive electrode Generally, there is a dilemma, the trade-off between optical transparency and conductivity for these materials taken alone makes them difficult to compete with commercial ITO In this work, a modified polyol synthesis method was adopted to grow single-crystal silver nanowire with controlled length by adding AgNO3 solution in advance and using high molecular weight polyvinylpyrrolidone (PVP) Ag nanowires ink was then spin coated onto flexible PET substrate to form Ag NW mesh, which shows impressive transparent and conductive (TC) property with sheet resistance of 23 Ω sq−1 and transmittance of 904% at a wavelength of 550 nm A post fluorine-doped ZnO (FZO) layer was then deposited by pulsed laser deposition method to improve the TC, stability and mechanical property High-quality Ag NW/FZO composite electrode was finally acquired at room temperature after optimizing the Ag NW length, concentration in suspension, and FZO layer thickness, with transmittance of 83% at wavelength of 550 nm, sheet resistance of 17 Ω sq−1, and high haze of 365% Perovskite solar cells incorporating such Ag NW/FZO composite electrode exhibited a better cell performance compared to the similar FTO-based perovskite solar cells

Wide tuning of the optical and structural properties of alternative plasmonic materials

Abstract: Alternative plasmonic materials have attracted considerable attention due to their advantages compared to conventional metals, including compatibility with Si processing, tunability of optical properties, and reduced losses. In this work, we demonstrate that post-deposition annealing of materials fabricated by magnetron sputtering allows large tuning of the structural and the optical dispersion properties of Indium Tin Oxide (ITO), Al-doped ZnO (AZO) and Titanium Nitride (TiN) nano-layers. By measuring their optical bandgaps, we show that thermal annealing treatments can dramatically modulate the carrier concentration in these materials, thus providing tunability of the optical losses and enabling the engineering of Epsilon-Near-Zero (ENZ) regime. Besides, we perform X-ray diffraction (XRD) measurements to show that thermal annealing can also effectively tune the materials grain sizes. Eventually, the effect of different annealing gases on the free carrier concentration has also been investigated. The wide tunability and control of the optical and structural properties that we demonstrated in this work is important to engineer resonant optical responses across a wide frequency spectrum for device applications to plasmonics, metamaterials and transformation-optics.

Highly Robust Silver Nanowire Network for Transparent Electrode.

Abstract: Solution-processed silver nanowire networks are one of the promising candidates to replace a traditional indium tin oxide as next-generation transparent and flexible electrodes due to their ease of processing, moderate flexibility, high transparency, and low sheet resistance. To date, however, high stability of the nanowire networks remains a major challenge because the long-term usages of these electrodes are limited by their poor thermal and chemical stabilities. Existing methods for addressing this challenge mainly focus on protecting the nanowire network with additional layers that require vacuum processes, which can lead to an increment in manufacturing cost. Here, we report a straightforward strategy of a sol–gel processing as a fast and robust way to improve the stabilities of silver nanowires. Compared with reported nanoparticles embedded in nanowire networks, better thermal and chemical stabilities are achieved via sol–gel coating of TiO2 over the silver nanowire networks. The conformal surface c...

Silver Nanowire Electrodes: Conductivity Improvement Without Post-treatment and Application in Capacitive Pressure Sensors

Abstract: Transparent electrode based on silver nanowires (AgNWs) emerges as an outstanding alternative of indium tin oxide film especially for flexible electronics. However, the conductivity of AgNWs transparent electrode is still dramatically limited by the contact resistance between nanowires at high transmittance. Polyvinylpyrrolidone (PVP) layer adsorbed on the nanowire surface acts as an electrically insulating barrier at wire–wire junctions, and some devastating post-treatment methods are proposed to reduce or eliminate PVP layer, which usually limit the application of the substrates susceptible to heat or pressure and burden the fabrication with high-cost, time-consuming, or inefficient processes. In this work, a simple and rapid pre-treatment washing method was proposed to reduce the thickness of PVP layer from 13.19 to 0.96 nm and improve the contact between wires. AgNW electrodes with sheet resistances of 15.6 and 204 Ω sq−1 have been achieved at transmittances of 90 and 97.5 %, respectively. This method avoided any post-treatments and popularized the application of high-performance AgNW transparent electrode on more substrates. The improved AgNWs were successfully employed in a capacitive pressure sensor with high transparency, sensitivity, and reproducibility.

Bendable ITO-free Organic Solar Cells with Highly Conductive and Flexible PEDOT:PSS Electrodes on Plastic Substrates

Abstract: Flexible and transparent electrodes have great potential for photon transmission and charge-carrier collection for next generation electronics compared to rigid electronics with indium tin oxide (ITO)-coated glass substrates. This study describes a comprehensive study of the electrical, morphological, optical, structural, and mechanical properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films treated by methanol and methanesulfonic acid (MSA), which are coated on hydrophobic flexible plastic substrates. Such a film coated on hydrophobic plastic substrates exhibits a high conductivity up to 3560 S cm–1 and a good mechanical flexibility. Moreover, the use of the films to fabricate bendable ITO-free organic solar cells (OSCs) integrated on plastic substrates was presented. The bendable devices based on P3HT:PCBM not only exhibit a high power conversion efficiency (PCE) up to 3.92%, which is comparable to 4.30% of the rigid devices with ITO-coated glass substrates, but also keep...

Solution-processed highly conductive PEDOT:PSS/AgNW/GO transparent film for efficient organic-Si hybrid solar cells.

Abstract: Hybrid solar cells based on n-Si/poly(3,4-ethylenedioxythiophene):poly(styrene- sulfonate) (PEDOT:PSS) heterojunction promise to be a low cost photovoltaic technology by using simple device structure and easy fabrication process. However, due to the low conductivity of PEDOT:PSS, a metal grid deposited by vacuum evaporation method is still required to enhance the charge collection efficiency, which complicates the device fabrication process. Here, a solution-processed graphene oxide (GO)-welded silver nanowires (AgNWs) transparent conductive electrode (TCE) was employed to replace the vacuum deposited metal grid. A unique “sandwich” structure was developed by embedding an AgNW network between PEDOT:PSS and GO with a figure-of-merit of 8.6 × 10–3 Ω–1, which was even higher than that of sputtered indium tin oxide electrode (6.6 × 10–3 Ω–1). A champion power conversion efficiency of 13.3% was achieved, because of the decreased series resistance of the TCEs as well as the enhanced built-in potential (Vbi) in ...

Low-Temperature High-Mobility Amorphous IZO for Silicon Heterojunction Solar Cells

Abstract: Parasitic absorption in the transparent conductive oxide (TCO) front electrode is one of the limitations of silicon heterojunction (SHJ) solar cells efficiency. To avoid such absorption while retaining high conductivity, TCOs with high electron mobility are preferred over those with high carrier density. Here, we demonstrate improved SHJ solar cell efficiencies by applying high-mobility amorphous indium zinc oxide ( a -IZO) as the front TCO. We sputtered a -IZO at low substrate temperature and low power density and investigated the optical and electrical properties, as well as subband tail formation—quantified by the Urbach energy ( $E_{U}$ )–as a function of the sputtering oxygen partial pressure. We obtain an $E_{U}$ as low as 128 meV for films with the highest Hall mobility of 60 cm2/V · s. When comparing the performance of a -IZO films with indium tin oxide (ITO) and hydrogenated indium oxide (IO:H), we find that IO:H (115 cm2 /V · s) exhibits a similar $E_{U}$ of 130 meV, while ITO (25 cm2/V · s) presents a much larger $E_{U}$ of up to 270 meV. The high film quality, indicated by the low $E_{U}$ , the high mobility, and low free carrier absorption of the developed a -IZO electrodes, result in a significant current improvement, achieving conversion efficiencies over 21.5%, outperforming those with standard ITO.

A Solution Processed Flexible Nanocomposite Electrode with Efficient Light Extraction for Organic Light Emitting Diodes

Abstract: Highly efficient organic light emitting diodes (OLEDs) based on multiple layers of vapor evaporated small molecules, indium tin oxide transparent electrode, and glass substrate have been extensively investigated and are being commercialized. The light extraction from the exciton radiative decay is limited to less than 30% due to plasmonic quenching on the metallic cathode and the waveguide in the multi-layer sandwich structure. Here we report a flexible nanocomposite electrode comprising single-walled carbon nanotubes and silver nanowires stacked and embedded in the surface of a polymer substrate. Nanoparticles of barium strontium titanate are dispersed within the substrate to enhance light extraction efficiency. Green polymer OLED (PLEDs) fabricated on the nanocomposite electrode exhibit a maximum current efficiency of 118 cd/A at 10,000 cd/m(2) with the calculated external quantum efficiency being 38.9%. The efficiencies of white PLEDs are 46.7 cd/A and 30.5%, respectively. The devices can be bent to 3 mm radius repeatedly without significant loss of electroluminescent performance. The nanocomposite electrode could pave the way to high-efficiency flexible OLEDs with simplified device structure and low fabrication cost.