Indium Tin Oxide Top Electrode Research Articles

P-i-n Perovskite Solar Cells on Steel Substrates.

An efficient substrate-configuration p–i–n metal-halide perovskite solar cell (PSC) is fabricated on a polymer-coated steel substrate. The optimized cell employs a Ti bottom electrode coated with a thin indium tin oxide (ITO) interlayer covered with a self-assembled [2-(9H-carbazol-9-yl)ethyl]phosphonic acid monolayer as a hole-selective contact. A triple-cation perovskite is used as the absorber layer. Thermally evaporated C60 and atomic layer deposited SnO2 layers serve to create an electron-selective contact. The cells use an ITO top electrode with an antireflective MgF2 coating. The optimized cell fabricated on a polymer-coated steel substrate reaches a power conversion efficiency of 16.5%, which approaches the 18.4% efficiency of a p–i–n reference superstrate-configuration cell that uses a similar stack design. Optical simulations suggest that the remaining optical losses are due to the absorption of light by the ITO top electrode, the C60 layer, the Ti bottom electrode, and reflection from the MgF2 coating in almost equal amounts. The major loss is, however, in the fill factor as a result of an increased sheet resistance of the top ITO electrode.

Bifunctional Graphene Oxide Hole-Transporting and Barrier Layers for Transparent Bifacial Flexible Perovskite Solar Cells

A thin graphene oxide (GO) layer has been prepared on indium tin oxide (ITO)-coated glass and plastic (polyethylene naphthalate; PEN) substrates for the application as a hole transport layer (HTL) of p–i–n-type planar perovskite solar cells. Transparent devices can be fabricated by replacing the Ag top electrode of conventional nontransparent devices with an ITO top electrode using radio frequency (RF) sputtering. The GO layer with high transmittance in the visible range exhibits excellent hole-extracting capabilities from the perovskite layer. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses reveal that the GO HTL uniformly covers the substrate. In addition, the GO-based devices show significantly improved long-term stability compared with the conventional poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based counterparts. The enhancement in stability becomes much more apparent for flexible devices with the PEN substrate, which has been attributed to the excellent barrier properties of the GO HTL. As a result, a transparent and flexible p-i-n-type perovskite solar cell with a bifunctional GO HTL exhibits a high efficiency of 9.34% (cf. 11.39% for the glass substrate and 12.31% for the nontransparent/glass substrate) and good long-term stability.

ALD of ZnO:Ti: Growth Mechanism and Application as an Efficient Transparent Conductive Oxide in Silicon Nanowire Solar Cells.

In the quest for the replacement of indium tin oxide (ITO), Ti-doped zinc oxide (TZO) films have been synthesized by atomic layer deposition (ALD) and applied as an n-type transparent conductive oxide (TCO). TZO thin films were obtained from titanium (IV) i-propoxide (TTIP), diethyl zinc, and water by introducing TiO2 growth cycle in a ZnO matrix. Process parameters such as the order of precursor introduction, the cycle ratio, and the film thickness were optimized. The as-deposited films were analyzed for their surface morphology, elemental stoichiometry, optoelectronic properties, and crystallinity using a variety of characterization techniques. The growth mechanism was investigated for the first time by in situ quartz crystal microbalance measurements. It evidenced different insertion modes of titanium depending on the precursor introduction, as well as the etching of Zn-Et surface groups by TTIP. Resistivity as low as 1.2 × 10-3 Ω cm and transmittance >80% in the visible range were obtained for 72-nm-thick films. Finally, the first application of ALD-TZO as TCO was reported. TZO films were successfully implemented as top electrodes in silicon nanowire solar cells. The unique properties of TZO combined with conformal coverage realized by the ALD technique make it possible for the cell to show almost flat external quantum efficiency (EQE) response, surpassing the bell-like EQE curve seen in devices with a sputtered ITO top electrode.

Low-power resistive random access memory by confining the formation of conducting filaments

Owing to their small physical size and low power consumption, resistive random access memory (RRAM) devices are potential for future memory and logic applications in microelectronics. In this study, a new resistive switching material structure, TiOx/silver nanoparticles/TiOx/AlTiOx, fabricated between the fluorine-doped tin oxide bottom electrode and the indium tin oxide top electrode is demonstrated. The device exhibits excellent memory performances, such as low operation voltage (<±1 V), low operation power, small variation in resistance, reliable data retention, and a large memory window. The current-voltage measurement shows that the conducting mechanism in the device at the high resistance state is via electron hopping between oxygen vacancies in the resistive switching material. When the device is switched to the low resistance state, conducting filaments are formed in the resistive switching material as a result of accumulation of oxygen vacancies. The bottom AlTiOx layer in the device structure limits the formation of conducting filaments; therefore, the current and power consumption of device operation are significantly reduced.

Improving Performance by Doping Gadolinium Into the Indium-Tin–Oxide Electrode in HfO2-Based Resistive Random Access Memory

This letter investigates the characteristics of doping gadolinium (Gd) in an indium-tin-oxide (ITO) electrode in HfO2-based resistive random access memory (RRAM). Identical bottom electrodes and insulators were made but then capped by either pure ITO or a Gd:ITO top electrode. Doping Gd in the ITO electrode produces lower operation currents in both high-resistance state (HRS) and low-resistance state (LRS) as well as enlarging the memory window. This excellent performance suggests a remarkable potential to improve RRAM applications. Schottky emission mechanism dominates both HRS and LRS according to current fitting results, and is confirmed by temperature effect experiments. The resistive switching behavior of the Gd:ITO device is explained by our model and is also confirmed by material analysis and electrical measurements. Furthermore, reliability tests verify the Gd:ITO device’s capability to perform data storage as a nonvolatile memory.

A high performance transparent resistive switching memory made from ZrO2/AlON bilayer structure

In this study, the switching properties of an indium tin oxide (ITO)/zirconium oxide (ZrO2)/ITO single layer device and those of a device with an aluminum oxynitride (AlON) layer were investigated. The devices with highly transparent characteristics were fabricated. Compared with the ITO/ZrO2/ITO single layer device, the ITO/ZrO2/AlON/ITO bilayer device exhibited a larger ON/OFF ratio, higher endurance performance, and superior retention properties by using a simple two-step forming process. These substantial improvements in the resistive switching properties were attributed to the minimized influence of oxygen migration through the ITO top electrode (TE), which can be realized by forming an asymmetrical conductive filament with the weakest part at the ZrO2/AlON interface. Therefore, in the ITO/ZrO2/AlON/ITO bilayer device, the regions where conductive filament formation and rupture occur can be effectively moved from the TE interface to the interior of the device.

ペロブスカイト太陽電池へのITO透明電極スパッタリング直接堆積の影響

Thin film solar cells using perovskite materials are very intensively studied since the perovskite materials such as CH3NH3PbI3 crystal have been found to show sensitizing effects on a TiO2 electron transport layer. This class of solar cell has made tremendous progress during the last few years, leading to a recently certified record power conversion efficiency (PCE) of 21.02%. In the perovskite /crystalline-Si (c-Si) tandem solar cell, furthermore, the theoretical value of PCE is expected as large as 35 %. Toward this application, the perovskite solar cell must be highly transparent at near-infrared wavelengths so that sufficient light is transmitted to the narrow-bandgap bottom cell. In this study, we fabricated the organic-lead halide perovskite solar cells comprising a transparent sputtered indium tin oxide (ITO) top electrode. We observed the PCE of 1.5% in transparent perovskite solar cells with a thin molybdenum oxide buffer layer and ITO electrode. Moreover, we obtained the PCE of 2% even in solar cells with ITO electrode sputtered directly on the organic charge transport layer. The photovoltaic property could be confirmed under the light irradiation from the ITO top electrode side.

Highly Transparent and Flexible Triboelectric Nanogenerators with Subwavelength-Architectured Polydimethylsiloxane by a Nanoporous Anodic Aluminum Oxide Template.

Highly transparent and flexible triboelectric nanogenerators (TENGs) were fabricated using the subwavelength-architectured (SWA) polydimethylsiloxane (PDMS) with a nanoporous anodic aluminum oxide (AAO) template as a replica mold. The SWA PDMS could be utilized as a multifunctional film for a triboelectric layer, an antireflection coating, and a self-cleaning surface. The nanopore arrays of AAO were formed by a simple, fast, and cost-effective electrochemical oxidation process of aluminum, which is relatively impressive for fabrication of the TENG device. For electrical contacts, the SWA PDMS was laminated on the indium tin oxide (ITO)-coated polyethylene terephthalate (PET) as a bottom electrode, and the bare ITO-coated PET (i.e., ITO/PET) was used for the top electrode. Compared to the ITO/PET, the SWA PDMS on the ITO/PET improved the transmittance from 80.5 to 83% in the visible wavelength region and also had high transmittances of >85% at wavelengths of 430-455 nm. The SWA PDMS also exhibited the hydrophobic surface with a water contact angle (θCA) of ∼115°, which can be useful for self-cleaning applications. The average transmittance (Tavg) of the entire TENG device was observed to be ∼70% over a broad wavelength range. At an external pushing frequency of 0.5 Hz, for the TENG device with the ITO top electrode, open-circuit voltage (VOC) and short-circuit current (ISC) values of ∼3.8 V and ∼0.8 μA were obtained instantaneously, respectively, which were higher than those (i.e., VOC ≈ 2.2 V, and ISC ≈ 0.4 μA) of the TENG device with a gold top electrode. The effect of external pushing force and frequency on the output device performance of the TENGs was investigated, including the device robustness. A theoretical optical analysis of SWA PDMS was also performed.

Facile fabrication and characterization of arch-shaped triboelectric nanogenerator with a graphite top electrode

We fabricated and characterized the polydimethylsiloxane (PDMS)-based triboelectric nanogenerators (TENGs) by employing a top electrode made of graphite. For a flexible electrode, the graphite was prepared on aluminum (Al) tape by a simple rolling process. By pressing a roller on the Al tape attached to a graphite substrate, the graphite flakes were entirely coated on its glue side for the graphite top electrode. For fabricating the TENG, the micro-pillar patterned PDMS as a triboelectric material was laminated on an indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrate as a bottom electrode. Under the external pushing forces of 0.1–0.3 kgf, the measured open-circuit voltage (Voc) and short-circuit current (Isc) of the TENG with the graphite top electrode were improved compared to the TENG with the ITO top electrode due to the superior electrical property. For the TENG with the graphite top electrode, the averaged Voc and Isc values were ∼1.80 V and 120.4 nA, respectively, at a frequency of 1 Hz (cf. Voc ∼0.97 V and Isc ∼69.3 nA for the TENG with the ITO top electrode). The effect of pushing frequency on the output performance of the fabricated TENG was also investigated.

Photovoltaic effect of lead-free (Na0.82K0.18)0.5Bi4.5Ti4O15 ferroelectric thin film using Pt and indium tin oxide top electrodes

We have grown a Bi-layer structure (Na0.82K0.18)0.5Bi4.5Ti4O15 (NKBiT) ferroelectric thin film on Pt(111)/TiO2/SiO2/Si(100) substrate by using the chemical solution deposition method and deposited two kinds of thin Pt and indium tin oxide (ITO) top electrodes. The photovoltaic behaviors of Pt/NKBiT/Pt and ITO/NKBit/Pt capacitors were investigated over the wavelength range of 300–500 nm. When NKBiT thin film is illuminated by the corresponding wavelength of the film's energy band gap (Eg), a photocurrent is generated due to the Schottky barrier between electrode and film, and an internal electric field is originated by the depolarization field. The maximum photocurrent density and power conversion efficiency of the ITO/NKBiT/Pt capacitor in the poled-up state are obtained as 45.75 nA/cm2 and 0.035%, respectively, at 352 nm. The photocurrent density and power conversion efficiency of the ITO/NKBiT/Pt capacitor increased to 3.5 times higher than that of the Pt/NKBiT/Pt capacitor.

Electrical Properties of Sol-Gel Derived PbLaZrTiOx Capacitors with Nonnoble Metal Oxide Top Electrodes

PbLaZrTiOx(PLZT) thin films were fabricated on Pt(111) substrateby the sol-gel method for ferroelectric capacitors. Pt top electrodeswere deposited by sputtering, aluminum-doped zinc oxide (AZO)or indium tin oxide (ITO) top electrodes were deposited by pulsedlaser deposition (PLD) on PLZT capacitors. We compared bothdegradation characteristics by annealing in 200°C, 1Torr, 3%hydrogen atmosphere and fatigue properties, exhibited the PLZTcapacitors with AZO and ITO top electrodes has better propertiescompared to the PLZT capacitors with Pt top electrodes.

Direct Formation of Transparent ITO Top Electrodes on High-Density ZnO Nanowires by Magnetron Sputtering

Transparent indium tin oxide (ITO) was directly deposited by magnetron sputtering to form two-dimensional top electrodes on vertically arrayed one-dimensional ZnO nanowires. Deposition at 5 mTorr resulted in almost complete coverage and interconnection of the nanowires, which maintained high transmittance. The use of lower pressure reduced ITO coverage over large areas of the nanowiresduetotheretardationoflateralcoalescence.ThesputteredITOlayersdidnotcovertheentirelengthsoftheZnOnanowires, although thin ITO coating was observed along the sidewalls of the nanowires for some distance from the surface. The ITO layers on the nanowire arrays had high conductivity, comparable to conventional In metal, because of the use of a plasma atmosphere and high temperature during deposition. This resulted in improved Ohmic contact and photodiode properties, which allowed direct electrical connection of the active nanowires without filling the spaces between them with insulating materials.

Electroluminescence from silicon nanoparticles fabricated from the gas phase

Electroluminescence from as-prepared silicon nanoparticles, fabricated by gasphase synthesis, is demonstrated. The particles are embedded between an n-dopedGaAs substrate and a semitransparent indium tin oxide top electrode. The totalelectroluminescence intensity of the Si nanoparticles is more than a factor of three higherthan the corresponding signal from the epitaxial III–V semiconductor. This, together withthe low threshold voltage for electroluminescence, shows the good optical properties ofthese untreated particles and the efficient electrical injection into the device. Impactionization by electrons emitted from the top electrode is identified as the origin of theelectrically driven light emission.

Capacitance and Interface Analysis of Transparent Analog Capacitor Using Indium Tin Oxide Electrodes and High-k Dielectrics

Transparent analog capacitors using indium tin oxide (ITO) electrodes and (and ) high- dielectrics were examined for optical device applications. The adoption of ITO bottom and top electrodes for the capacitors did not degrade the electrical properties of the capacitors compared to titanium nitride (TiN) and Pt electrodes. Compared to conventional analog capacitors using TiN electrodes, capacitors using ITO electrodes show a larger capacitance at the negative voltages in the capacitance–voltage curve. This suggests the presence of a thicker depletion layer at the top electrode, which is probably due to the high resistivity of the Sn-rich top ITO initial layer on the dielectric film. Before and after a subsequent thermal annealing, the curve of was barely changed, while that of showed significant variations. This was attributed to the change in the composition at the interface (i.e., Hf diffusion and oxygen deficiency) rather than to the change in the crystallinity of ITO and .