Conventional Indium Tin Oxide Film Research Articles

Vanadium-doped indium tin oxide window layer in Sb2Se3 solar cell

Antimony selenide (Sb2Se3) is an emerging photovoltaic material. Indium tin oxide (ITO) is commonly used as the window layer material in Sb2Se3 solar cells; however, ITO films have poor absorption in the near-infrared spectrum. Our objective in this research was to replace conventional ITO with vanadium-doped indium tin oxide (ITO:V) to improve the near-infrared light transmittance of Sb2Se3 thin film solar cells and thereby enhance the efficiency of solar cells. The experiment parameters included vanadium doping concentration and annealing temperature. ITO films doped with 0.35 at.% V and annealed at 100 °C for 30 min outperformed conventional ITO films in terms of photovoltaic performance. The proposed scheme improved light transmittance from 80.03% to 83.02% over a wavelength range of 400–1100 nm, which led to a significant improvement in Jsc and device efficiency (from 4.5% to 5.6%). It appears that ITO films can be doped with vanadium to improve transmittance by reducing refractive index degradation in the near-infrared region.

Superior optoelectrical properties of magnetron sputter-deposited cerium-doped indium oxide thin films for solar cell applications

Indium tin oxide (ITO) is the most commonly used front contact material for a variety of photovoltaic technologies. However, the presence of a high free carrier concentration in ITO thin films results in the well-known phenomenon of free carrier absorption in the near-infrared (NIR) region of the solar spectrum. This causes optical losses especially in those solar cells where the active layer is designed to preferentially absorb NIR photons. Therefore, a combination of high carrier mobility and high NIR transparency is desired for advanced transparent conductive oxides for substituting ITO in solar cells. In this work, cerium-doped indium oxide (ICeO) thin films are deposited by pulsed DC magnetron sputtering, giving a remarkable 137% improvement of the mobility (71 cm2 V−1 s−1) compared to the previous record value of 30 cm2 V−1 s−1 for DC magnetron sputtered cerium-doped ITO films on glass. When compared to conventional ITO films prepared in this work, the highest mobility of ICeO is found to be almost four times higher and also the NIR transmission is substantially enhanced. Theoretical modelling of the experimental results indicates that neutral impurity scattering limits the carrier mobility in our films. With the recent advancements in single and multi-junction organic and perovskite solar cells, the development of ICeO/glass substrates (as possible replacements for the commonly used ITO/glass substrates) demonstrates significant potential in minimizing optical losses in the NIR region.

Highly Flexible and Transparent Ag Nanowire Electrode Encapsulated with Ultra-Thin Al2O3: Thermal, Ambient, and Mechanical Stabilities

There is an increasing demand in the flexible electronics industry for highly robust flexible/transparent conductors that can withstand high temperatures and corrosive environments. In this work, outstanding thermal and ambient stability is demonstrated for a highly transparent Ag nanowire electrode with a low electrical resistivity, by encapsulating it with an ultra-thin Al2O3 film (around 5.3 nm) via low-temperature (100 °C) atomic layer deposition. The Al2O3-encapsulated Ag nanowire (Al2O3/Ag) electrodes are stable even after annealing at 380 °C for 100 min and maintain their electrical and optical properties. The Al2O3 encapsulation layer also effectively blocks the permeation of H2O molecules and thereby enhances the ambient stability to greater than 1,080 h in an atmosphere with a relative humidity of 85% at 85 °C. Results from the cyclic bending test of up to 500,000 cycles (under an effective strain of 2.5%) confirm that the Al2O3/Ag nanowire electrode has a superior mechanical reliability to that of the conventional indium tin oxide film electrode. Moreover, the Al2O3 encapsulation significantly improves the mechanical durability of the Ag nanowire electrode, as confirmed by performing wiping tests using isopropyl alcohol.

Bendable Solar Cells from Stable, Flexible, and Transparent Conducting Electrodes Fabricated Using a Nitrogen‐Doped Ultrathin Copper Film

Copper has attracted significant interests as an abundant and low‐cost alternative material for flexible transparent conducting electrodes (FTCEs). However, Cu‐based FTCEs still present unsolved technical issues, such as their inferior light transmittance and oxidation durability compared to conventional indium tin oxide (ITO) and silver metal electrodes. This study reports a novel technique for fabricating highly efficient FTCEs composed of a copper ultrathin film sandwiched between zinc oxides, with enhanced transparency and antioxidation performances. A completely continuous and smooth copper ultrathin film is fabricated by a simple room‐temperature reactive sputtering process involving controlled nitrogen doping (<1%) due to a dramatic improvement in the wettability of copper on zinc oxide surfaces. The electrode based on the nitrogen‐doped copper film exhibits an optimized average transmittance of 84% over a spectral range of 380 −1000 nm and a sheet resistance lower than 20 Ω sq−1, with no electrical degradation after exposure to strong oxidation conditions for 760 h. Remarkably, a flexible organic solar cell based on the present Cu‐based FTCE achieves a power conversion efficiency of 7.1%, clearly exceeding that (6.6%) of solar cells utilizing the conventional ITO film, and this excellent performance is maintained even in almost completely bent configurations.

Fabrication of Large Area, High‐Performance, Transparent Conducting Electrodes Using a Spontaneously Formed Crackle Network as Template

A single micro/nanowire network of a metal deposited over a large area on a transparent substrate serves as a transparent conducting electrode with optoelectronic properties that are enhanced in many ways relative to the conventional indium tin oxide films. The wire surface is extremely smooth and the junctions are seamless, thanks to the crackle lithography process. The method is applicable to various metals and hybrid materials as well as to flexible and curved substrates.

Enhanced output power of (indium) gallium nitride light emitting diodes by a transparent current spreading-film composed of a disordered network of indium tin oxide nanorods

A thin film consisting of a disordered nanorod network of indium tin oxide (ITO) and conventional ITO films are fabricated on gallium nitride (GaN) based-light emitting diodes (LEDs) by electron beam evaporation. The surface morphologies are observed by scanning electron microscopy (SEM). The disordered nanorod network of ITO is grown in vacuum without oxygen. It can be applied directly on the LED as the current spreading film unlike other nanorods which require growth on a conductive layer. The transmittance, current–voltage characteristic, and the dependence of light output power on current are measured for disordered nanorod network ITO LEDs and conventional ITO LEDs, respectively. The measurement results indicate that the nanorod network provides a significant improvement in the light output power of GaN-based LEDs. The influence of the structure of ITO films on the light output power of GaN-based LEDs is discussed.

Formation of uniformly sized gold nanoparticles over graphene by MeV electron beam irradiation for transparent conducting films

Highly flexible, transparent, and conducting sheet was fabricated by decoration of uniformly sized gold nanoparticles (Au NPs) with high-density on large-area graphene by MeV electron beam irradiation (MEBI) at room temperature under ambient conditions. The Au NPs with an average size of 13.6 ± 3.5 nm were clearly decorated on the graphene after MEBI with an irradiation energy of 1.0 MeV. The sheet resistances of the Au NPs/graphene significantly decreased. For the Au NPs/trilayer graphene, the sheet resistance reached to ∼45 Ω/sq, and the optical transmittance was ∼90.2% which is comparable to that of conventional indium tin oxide film.

Effect of thickness and substrate temperature on the properties of transparent Ti-doped In2O3 films grown by direct current magnetron sputtering

We reported on the effect of film thickness and substrate temperature on the properties of TiO2-doped In2O3 (TIO) films deposited on a glass substrate by direct current (DC) magnetron sputtering for touch panel applications. The electrical, optical, surface and structural properties of TIO films grown at room temperature were significantly dependent on its thickness. At optimized TIO thickness (480nm), the resistivity of the TIO film decreased with increasing substrate temperature due to effective activation of Ti dopant and crystallization of the In2O3 matrix. Furthermore, the increase in substrate temperature during DC sputtering leads to increase of optical bandgap of the TIO films due to Burstein–Moss effect, which is caused by change in carrier concentration of TIO films. At optimized conditions, the TIO film shows resistivity of 1.947×10−4Ω-cm and optical transmittance of 85.3% comparable conventional indium tin oxide films.

Indium tin oxide subwavelength nanostructures with surface antireflection and superhydrophilicity for high-efficiency Si-based thin film solar cells

We fabricated the parabola-shaped subwavelength grating (SWG) nanostructures on indium tin oxide (ITO) films/Si and glass substrates using laser interference lithography, dry etching, and subsequent re-sputtering processes. The efficiency enhancement of an a-Si:H/μc-Si:H tandem thin film solar cell was demonstrated theoretically by applying the experimentally measured data of the fabricated samples to the simulation parameters. Their wetting behaviors and effective electrical properties as well as optical reflectance properties of ITO SWGs, together with theoretical prediction using a rigorous coupled-wave analysis method, were investigated. For the parabola-shaped ITO SWG/ITO film, the solar weighted reflectance (SWR) value was ~10.2% which was much lower than that (i.e., SWR~20%) of the conventional ITO film, maintaining the SWR values less than 19% up to a high incident angle of 70° over a wide wavelength range of 300-1100 nm. Also, the ITO SWG with a superhydrophilic surface property (i.e., water contact angle of 6.2°) exhibited an effective resistivity of 2.07 × 10(-3) Ω-cm. For the a-Si:H/μc-Si:H tandem thin film solar cell structure incorporated with the parabola-shaped ITO SWG/ITO film as an antireflective electrode layer, the conversion efficiency (η) of 13.7% was theoretically obtained under AM1.5g illumination, indicating an increased efficiency by 1.4% compared to the device with the conventional ITO film (i.e., η = 12.3%).

An ITO/Au/ITO Thin Film Gas Sensor for Methanol Detection at Room Temperature

Indium tin oxide (ITO) films with a 5 nm thick Au interlayer were prepared on glass substrates. The effects of the Au interlayer on the gas sensitivity for detecting methanol vapors were investigated at room temperature. The conductivity of the film sensor increased upon exposure to methanol vapor and the sensitivity also increased proportionally with the methanol vapor concentration. In terms of the sensitivity measurements, the ITO film sensor with an Au interlayer shows a higher sensitivity than that of the conventional ITO film sensor. This approach is promising in gaining improvement in the performance of ITO gas sensors used for the detection of methanol vapor at room temperature.

Characterization of a Crystallized ZnO/CuSn/ZnO Multilayer Film Deposited with Low Temperature Magnetron Sputtering

The ZnO/CuSn/ZnO (ZCSZ) multilayer films were deposited on polycarbonate substrates using reactive RF and DC magnetron sputtering. The thickness of each layer was 50 nm/5 nm/45 nm, respectively. The ZCSZ films showed a sheet resistance of <TEX>$44{\Omega}$</TEX>/Sq, which was an order of magnitude lower than that indium tin oxide (ITO) films. Although the ZCSZ films had a CuSn interlayer that absorbed visible light, both films had similar optical transmittances of 74% in the visible wavelength region. The figure of merit of the ZCSZ films was <TEX>$1.0{\times}10^{-3}{\Omega}^{-1}$</TEX> and was greater than the value of the ITO films, <TEX>$1.6{\times}10^{-4}{\Omega}^{-1}$</TEX>. From the X-ray diffraction (XRD) analysis, the ITO films did not show any diffraction peaks, whereas the ZCSZ films showed diffraction peaks for the ZnO (100) and (002) phases. The hardness of the ITO and ZCSZ films were 5.8 and 7.1 GPa, respectively, which were determined using nano-indentation. From these results, the ZCSZ films exhibited greater optoelectrical performance and hardness compared to the conventional ITO films.

Growth of Transparent Conductive Al-Doped ZnO Thin Films and Device Applications

High-purity transparent conductive Al-doped ZnO (AZO) films were grown by KrF excimer pulsed laser deposition. We used ultraviolet and X-ray photoelectron spectroscopes to directly measure the absolute values of the vacuum work function of AZO films. The structure and electrical and optical properties of the as-grown AZO films were studied using X-ray diffraction, room temperature Hall effect measurement and spectro photometer, respectively. Finally, organic light emitting diodes (OLED) were fabricated on these AZO films. OLED device measurement showed that the current of the OLED with AZO was clearly increased. Our AZO thin films showed a higher conductivity (ρ=1.33×10-4 Ω cm, Rs=10.1 Ω/sq) than conventional indium tin oxide films.