Gallium-doped Zinc Oxide Research Articles

Highly Transparent Conductive Gallium-Doped Zinc Oxide Thin Films Grown by Reactive Plasma Deposition for Silicon Heterojunction Solar Cells

Highly Transparent Conductive Gallium-Doped Zinc Oxide Thin Films Grown by Reactive Plasma Deposition for Silicon Heterojunction Solar Cells

Tuneability and optimum functionality of plasmonic transparent conducting oxide-Ag core-shell nanostructures

Tunning localized surface plasmon resonance (LSPR) in transparent conducting oxides (TCO) has a great impact on various LSPR-based technologies. In addition to the commonly reported mechanisms used for tunning LSPR in TCOs (e.g., size, shape, carrier density modifications via intrinsic and extrinsic doping), integrating them in core-shell structures provides an additional degree of freedom to expand its tunability, enhance its functionality, and widen its versatility through application-oriented core-shell geometrical optimization. In this work, we explore the tuneability and functionality of two TCO nanostructures; indium doped tin oxide (ITO) and gallium doped zinc oxide (GZO) encapsulated with silver shell within the extended theoretical Mie theory formalism. The effect of core and shell sizes on LSPR peak position and line width as well as absorption and scattering coefficients is numerically investigated. Simulations showed that LSPRs of ITO-Ag and GZO-Ag core-shell nanostructures have great tunning capabilities, spanning from VIS to IR spectral range including therapeutic window of human tissue and essential solar energy spectrum. Potential functionality as refractive index sensor (RIS) and solar energy absorber (SEA) are examined using appropriate figure of merits (FoM). Simulations indicate that a geometrically optimized core-shell architecture with exceptional FoMs for RIS and SEA can be realized. Contrary to carrier density manipulation, integrating TCO cores to metallic shells proves to be an effective approach to enhance tunability and optimize functionality for high performance TCO-based plasmonic devices, with minimum impact on the inherited physical and chemical properties of the used TCO-core materials.

Experimental analysis of free-standing and substrate-constrained Ga-doped ZnO nanostructured thermoelectric films

Developing thermoelectric films without substrates—free-standing films—eliminates substrate-induced effects on performance and meets the flexibility requirements of emerging wearable thermoelectric applications. This study investigates Gallium-doped Zinc Oxide (GZO), composed of abundant and non-toxic elements, to fabricate a substrate-free GZO film via 3D printing and compares its structural, chemical, and thermoelectric properties with those of a substrate-constrained GZO film produced through chemical deposition. Both films exhibited uniform crystal structures and phase purity; however, the substrate-constrained film displayed additional diffraction peaks, suggesting potential substrate interactions. The 3D-printed free-standing film effectively eliminated the tensile stresses observed in the substrate-constrained film. FE-STEM analysis revealed nanostructures with homogeneous elemental distribution in both films, though the substrate-constrained film showed discontinuities, such as pores, likely caused by post-deposition annealing treatment. XPS analysis highlighted differences in chemical states and elemental compositions between the films, influenced by fabrication methods, substrate-induced stresses, and surface energy mismatches. The free-standing GZO film developed through 3D printing exhibited a more balanced incorporation of Zn and O, as it was not subject to substrate or post-deposition annealing constraints. Consequently, it demonstrated a 14 % increase in electrical conductivity and a 91 % improvement in the Seebeck coefficient compared to the substrate-constrained film, resulting in a higher room-temperature power factor of 261 nW/m·K2. These findings underscore the potential of 3D-printed free-standing GZO films to advance thermoelectric applications, offering a promising alternative to overcome the challenges of substrate-constrained films and further drive innovation in the field.

Unveiling the potential: Gallium-doped zinc oxide/silver-nanoparticles/glass structure for superior anode performance in polymer light-emitting diodes

This study examines the effectiveness of gallium-doped zinc oxide (GZO) combined with silver nanoparticles (Ag-NPs) on glass substrates as anodes for polymer light-emitting diodes (PLEDs). The proposed GZO/Ag-NPs/glass structure achieved superior electrical and optical properties, with a peak luminance of 5834 cd/m2 and an average current efficiency of 1.91 cd/A, significantly outperforming the conventional GZO/Ag-NPs/GZO/glass anode. The GZO/Ag-NPs/glass anode enhanced electroluminescence intensity by 379 % compared to the GZO/glass anode, while the GZO/Ag-NPs/GZO/glass anode showed a 196 % enhancement. This highlights the potential for improved PLED performance through enhanced anode conductivity and localized surface plasmon resonance effects.

3D printing flexible Ga-doped ZnO films for wearable energy harvesting: thermoelectric and piezoelectric nanogenerators

The 3D printing of energy harvesters using earth-abundant and non-toxic elements promotes energy sustainability and market competitiveness. The semiconducting behavior and non-centrosymmetric wurtzite crystal structure of gallium-doped zinc oxide (GZO) films make them attractive for thermoelectric and piezoelectric nanogenerators. This study investigates the thermal, structural, mechanical, thermoelectric, and piezoelectric properties of 3D-printed GZO nanocomposite films. Thermal analysis demonstrates the stability of the nanocomposite film up to 230 °C, making it suitable for wearable energy harvesters. The crystalline structure of the nanocomposite film aligns with the hexagonal wurtzite structure of ZnO and displays a bulk-like microstructure with a uniform distribution of elements. The presence of Ga 2p, Zn 2p, O 1 s, and C 1 s core levels confirms the development of the nanocomposite film, characterized by a fine granular structure and a conductive domain compared to the neat resin film. The inclusion of GZO nanofillers tailors the stress–strain behavior of the nanocomposite film, enhancing flexibility. The 3D-printed GZO nanocomposite films demonstrate a promising thermoelectric power factor and piezoelectric power densities, along with mechanical flexibility and thermal stability. These advancements hold significant potential for wearable and hybrid energy generation technologies.

Retraction Note: Gallium-doped zinc oxide nanoparticles as biocompatible and promising nanocarrier for delivery of anticancer drug Adrucil

Retraction Note: Gallium-doped zinc oxide nanoparticles as biocompatible and promising nanocarrier for delivery of anticancer drug Adrucil

Optimization of electrochromic performance of WO3−x films grown by RF sputtering on gallium-doped zinc oxide

The present paper investigates the sputtered tungsten oxide thin films on gallium-doped zinc oxide-coated glass substrates concerning electrochromic behavior since the most promising candidate of smart glass in the future. Concordantly, each of the deposition parameters, including sputter power, total pressure, and O2/Ar + O2 gas ratio in the plasma, were examined in terms of electrochromic applications to enable to use of these values to be brought to large scale in commercial applications. As a result of comprehensive and systematic optimization studies, the optical modulation values were reached from 63.1 % to 70.8 % and the time needed for coloration and bleaching was observed as 7 and 5 s with final deposition values as 45 W power, 10 mTorr pressure, and 25 % O2 ratio. Additionally, whilst durability is still a problem in electrochromic coatings, reasonable durability cycling was achieved after 900 switching without encapsulation.

Gallium‐Doped Zinc Oxide/Tungsten‐Doped Indium Oxide Stacks with Enhanced Lateral Transport Capability for Efficient and Low‐Cost Silicon Heterojunction Solar Cells

To decrease the series resistance in front gallium‐doped zinc oxide (GZO) silicon heterojunction (SHJ) solar cells caused by high‐resistivity GZO films, stack films including tungsten‐doped indium oxide (IWO) films which have better lateral transport properties are used as the front transparent conductive oxide (TCO) to improve charge transport. The crystal structure and electrical and optical characteristics of GZO/IWO stacks with different thickness ratios are investigated, and the current–voltage performance of SHJ solar cells with front GZO/IWO stacks and rear GZO film are analyzed. The effective transmittance of the stacks is greater than 98% in the visible region. When the thickness of GZO/IWO is 50 nm:50 nm, the resistivity reaches 8.59 × 10−4 Ω cm, which is a significantly 70% reduction compared with that of a single GZO film. Meanwhile, the power conversion efficiency is improved to 23.8%, effectively reducing the efficiency gap by approximately 0.12% compared to a single IWO transparent electrode. More effective lateral transport lowers the series resistance of SHJ solar cells. By employing stacks with lower indium content in the front TCO of SHJ solar cells, the cost can be reduced without significantly affecting the efficiency, which is important for the large‐scale development of SHJ solar cells.

Enhanced antimicrobial and photocatalytic effects of plasma-treated gallium-doped zinc oxide

We characterize gallium-doped zinc oxide (ZnO:Ga) after exposure to hydrogen or oxygen plasma for potential use as a novel antibacterial and photocatalytic material. ZnO:Ga were composed of smooth rods with a thick central portion and tapered nanometre-sized ends alongside clusters of thin disk particles. Plasma treatment removed material from the rod surface and introduced features such as small holes or pits that increased the surface roughness and reduced the zinc ion concentration measured from colloidal suspensions. The surface charge of ZnO:Ga was influenced by plasma treatment: hydrogen plasma induced a positive surface charge whereas oxygen plasma resulted in a negative surface charge. However, electrostatic interactions with negatively charged bacteria were not the predominant mechanism underlying the antibacterial effect of ZnO:Ga. Treatment with oxygen or hydrogen plasma enhanced the antibacterial effect of ZnO:Ga against gram-positive bacteria, yet only oxygen plasma caused an enhancement against gram-negative bacteria. The photocatalytic effect of ZnO:Ga was enhanced after oxygen plasma treatment but supressed by hydrogen plasma treatment. The results indicate that plasma treatment of ZnO:Ga can successfully alter material properties to provide enhancement of the antibacterial and photocatalytic effects, however the type of feed gas used should be carefully chosen based upon the desired application.

Strain-induced photoresponsivity in gallium-doped ZnO thin film based UV photodetectors

The effect of varying Ga-doping on structural, optical, and UV detection properties of ZnO/p-Si based photodetectors is reported in this paper. Herein, the pure and gallium (Ga) (1 at%, 2 at%, and 3 at%) doped ZnO thin films are deposited on p-Si substrates by the sol–gel spin-coating method. On the basis of characteristic investigations, it is found that the varying Ga-doping affects not only the structural and optical properties of ZnO films, but also their electrical characteristics and hence significantly changes the performance of the devices employing ZnO films. Moreover, it is observed that the band gap size of the films is linearly dependent on strain values. As for the photodetector performance, it is found that the photodetector with 2 at% Ga doped ZnO demonstrates an excellent device performance, yielding a RR of 7908, PDCR of 171.7, PR of 8.15 (A/W) with D* of 5.4 × 1012 Jones, EQE of 2769.5%, and G of 27.69. The results suggest that the resulting device has a high potential for UV sensor applications.

Sensitivity enhancement of the surface plasmon resonance sensor based on gallium-doped zinc oxide and silicon for cancer detection: A wavelength interrogation approach

Surface plasmon resonance (SPR) sensors have become an essential tool for the label-free and immediate detection of biomolecular interactions. This paper presents a unique method for increasing the sensitivity of an SPR sensor designed for cancer detection. We offer a sensor design that promises improved detection capabilities using the unique characteristics of silicon (Si) and gallium-doped zinc oxide (GZO). The method uses a wavelength interrogation technique to precisely monitor biomolecular interactions by taking advantage of the spectrum changes SPR brings. The sensor's potential for detecting early-stage cancer is shown by numerical findings that support a considerable improvement in sensitivity to 1711.7 nm/RIU for Basal cancer cells. A promising route for developing biological sensing technologies is the combination of GZO and Si in the SPR sensor, wavelength interrogation, transfer matrix method (TMM)-based reflectance computation, and the attenuated total reflection principle.

High transparent conductive Ga-doped ZnO-based multilayer thin films with embedded ultrathin TiN layer deposited in oxygen-containing atmosphere.

To avoid metal layer oxidation during the deposition of transparent conductive oxide (TCO)/metal/TCO multilayer films in an oxygen-containing atmosphere, the ultra-thin (<10 nm) titanium nitride (TiN) layer has been proposed to replace metal embedding in gallium-doped zinc oxide (GZO) film for the development of indium-free transparent electrodes. The effects of TiN thickness on the structure, morphology, electrical, and optical properties of GZO/TiN/GZO multilayer thin films deposited in argon-oxygen mixtures on glass substrates by magnetron sputtering are investigated. The experimental results reveal that multilayers with the 8 nm-thick TiN layer have the optimal performance (figure of merit of 2.75 × 10-1 Ω-1): resistivity of 4.68 × 10-5 Ω cm, and optical transmittance of above 91% in the visible region, which is superior to the sandwich film with the metal embedded layer.

RETRACTED ARTICLE: Gallium-doped zinc oxide nanoparticles as biocompatible and promising nanocarrier for delivery of anticancer drug Adrucil

RETRACTED ARTICLE: Gallium-doped zinc oxide nanoparticles as biocompatible and promising nanocarrier for delivery of anticancer drug Adrucil

Effects of Post-Annealing on the Properties of ZnO:Ga Films with High Transparency (94%) and Low Sheet Resistance (29 Ω/square).

This study presents gallium-doped zinc oxide (ZnO:Ga, GZO) thin films. GZO thin films with both high transparency and low sheet resistance were prepared by RF sputtering and then post-annealed under nitrogen and hydrogen forming gas. With post-annealing at 450 °C, the proposed films with a film thickness of 100 nm showed high transparency (94%), while the sheet resistance of the films was reduced to 29 Ω/square, which was comparable with the performances of commercial indium tin oxide (ITO) samples. Post-annealing under nitrogen and hydrogen forming gas enhanced the films' conductivity while altering the thin-film composition and crystallinity. Nitrogen gas played a role in improving the crystallinity while maintaining the oxygen vacancy of the proposed films, whereas hydrogen did not dope into the thin film, thus maintaining its transparency. Furthermore, hydrogen lowered the resistance of GZO thin films during the annealing process. Then, the detailed mechanisms were discussed. Hydrogen post-annealing helped in the removal of oxygen, therefore increasing the Ga3+ content, which provided extra electrons to lower the resistivity of the films. After the preferable nitrogen/hydrogen forming gas treatment, our proposed films maintained high transparency and low sheet resistance, thus being highly useful for further opto-electronic applications.

Transparent conducting oxides (TCOs) based gratings for light absorption in near infrared spectrum

The present work examines the absorption enhancement of Transparent Conducting Oxides (e.g., Aluminum doped Zinc Oxide (AZO), Gallium doped Zinc Oxide (GZO), and Indium doped Tin Oxide (ITO) for widely used telecom spectral window around λ = 1550 nm. This is by virtue of the fact that the silica-based optical fiber exhibits minimum loss in this window. It is well established that one-dimensional metallic lamellar grating can significantly enhance light absorption through diffraction and excitation of surface plasmon polaritons (SPPs) at the metal-dielectric interface. This results in subwavelength confinement and hence, enhanced optical absorption in the absorbing layer near the grating. The absorption enhancement can be tuned in different spectral regions by controlling grating parameters, such as grating period, grating height, and grating aspect ratio. The present work focused on establishing Transparent Conducting Oxides (TCOs) as effective plasmonic materials for metallic grating to optimize optical absorption in the near-infrared (NIR) spectral region. The role of TCOs and the grating parameters in fine-tuning the optical absorption enhancement is investigated. Moreover, TCO grating-based designs optimized for absorption enhancement in and around the telecommunication wavelength are proposed.

Over 23% Efficiency Under Indoor Light in Gallium-Doped Zinc Oxide Electron-Transport-Layer-Based Inverted Organic Solar Cell to Power IoT Devices

Inverted structured organic solar cells (OSCs) have recently attracted attention due to their greater stability and performance above conventional structured OSCs. Consequently, under indoor lighting, OSCs have excellent power conversion efficiency (PCE). Indoor OSC may be a useful power source for a variety of electrical devices connected to the Internet of Things network. An inverted structured OSC, the electron transport layer (ETL) is crucial. Inverted OSCs have been constructed with variety of metal oxides based ETL. Zinc oxide (ZnO) is one of the best options among them because of its high transparency and stability, but its lower electron mobility is the key reason for the ZnO ETL-based inverted OSCs’ lower PCE. Moreover, very few studies have been conducted on the application of inverted structured OSCs for indoor light harvesting. We fabricate ZnO and gallium (Ga)-doped ZnO (GZO) ETL-based inverted structured OSCs with an poly (2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo1,2-b:4,5-b’dithiophene))-alt-(5,5-(1’,3’-di-2-thienyl-5’,7’-bis(2-ethylhexyl)benzo1’,2’-c:4’,5’-c’dithiophene-4,8-dione):6,6-phenyl-C71-butyric acid methyl ester (PBDB-T:PC70BM) active layer and evaluate them using a light-emitting diode (LED) (1000 lx). To optimize the doping concentration, we have varied the concentration of Ga in the GZO. The findings demonstrate that only by doping the ETL of the inverted structured OSC, the PCE may be significantly enhanced. Under a 1000 lx LED illumination, the device using undoped ZnO as the ETL shows a maximum of 15.56% PCE. The OSC with Ga-doped ZnO as the ETL with an optimized concentration of Ga (2 at.%) exhibits a maximum of 23.42% PCE under a 1000 lx LED.

Preparation, optimization and electrochromic properties of dual-band device with four modes

A dual-band electrochromic device with four modes was fabricated to selective modulate the transmittance from visible to near-infrared bands for the energy-saving field. The new LiClO4 + TBACl + AgNO3 electrolyte was prepared to respectively regulate the redox reactions of silver ion and lithium ion to prove the four modes of the device. The dual-band device with a sandwich structure was fabricated by the titanium dioxide electrochromic film, the gallium doped zinc oxide ion storage film and the LiClO4 + TBACl + AgNO3 electrolyte. The titanium dioxide and gallium doped zinc oxide films were prepared by a nanoparticle deposition system, which is an environmentally friendly dry deposition technique. By controlling the supplied potential, the redox reactions of silver ion and lithium ion present four modes, including transparent mode, warm mode, cold mode and full block mode. For warm mode, the localized surface plasmon resonance effect was excited by generating silver nanoparticles using two-stage potential. Moreover, the titanium dioxide film with high surface roughness shown the large light scattering effect, the transmittance of ∼0% at whole wavelengths was obtained in full block mode. The electrochromic device shown the large transmittance modulation (71%) and excellent cyclic stability (600 cycles). Therefore, it is proved that the transmittance can be adjusted at a specific wavelength by the electrochromic device, which provides an effective way for developing dual-band smart devices to reduce energy consumption.

Weak UV-Stimulated Synaptic Transistors Based on Precise Tuning of Gallium-Doped Indium Zinc Oxide Nanofibers

Weak UV-Stimulated Synaptic Transistors Based on Precise Tuning of Gallium-Doped Indium Zinc Oxide Nanofibers

Gallium-Modified Zinc Oxide Thin Films Prepared by Chemical Solution Deposition

Gallium-doped ZnO (GZO) thin films on glass, which can be used as transparent electrodes, were prepared using a spin coating technique. Thermal analysis and Fourier-transform infrared spectroscopy of the dried precursor solution of Zn acetate and Ga nitrate dissolved in ethanol with diethanolamine confirmed the decomposition of the organic components upon heating and the formation of ZnO at 450 °C. The thin films fired at 600 °C in oxygen and air, and the films annealed at 400 °C in Ar/H2, were polycrystalline, 140 nm thick, and exhibited a homogeneous microstructure with 50 nm grains and a smooth surface, as shown by X-ray powder diffraction and scanning electron and atomic force microscopy. The sheet resistance Rs measured using the 4-probe technique showed a change in Rs within 80 days for all samples. The Rs of the GZO thin films annealed in oxygen and air with values of MΩ/sq decreased over time. Rs values of 150 kΩ/sq were obtained for GZO thin films annealed in Ar/H2, but the Rs increased over time. We suggest that the degradation of Rs is related to the adsorption of water on GZO and that the responses depend on the nature of the defects in the GZO lattice.

Facile and versatile fabrication process for AgNW/GZO transparent composite electrodes for photovoltaic applications by atmospheric pressure plasma jet

Transparent conductive oxide (TCO) must have high electrical conductivity and optical transmittance. Using higher doping concentrations improves the conductivity but often at the expense of transmittance in the near-infrared regime. Using thicker film to improve the conductivity is not preferable as it significantly reduces the transmittance. Silver nanowire (AgNW)/ TCO composite film has been proposed as a viable method to address this dilemma. However, AgNWs often require additional thermal treatment to weld the nanowires to reduce the contact resistance. Also, thermal treatment apparatus, such as lasers, cannot be easily integrated into the TCO deposition setup, adding extra cost for handling samples. Here we use an atmospheric pressure plasma jet (APPJ) to fabricate AgNW/ TCO composite films—APPJ successfully welds the AgNWs and covers them with a thin gallium-doped ZnO or GZO protective layer simultaneously. The AgNW weight significantly affects the optoelectronic and morphological properties and can be tailored to fit the requirements of particular photovoltaic applications. Our perovskite solar cells with the AgNW/GZO front electrodes exhibit a ∼21% increase in power conversion efficiency. Furthermore, unlike conventional methods, our approach is vacuum-free and does not require additional processes, such as lasers, to treat the AgNW network, which may greatly reduce operational complexity.