Alloying In2O3 and Ga2O3 on AlN templates for deep-ultraviolet transparent conductive films by mist chemical vapor deposition

We studied the phase diagram of (In x Ga1−x )2O3 thin films with a composition of x = 0 to 1 on Aluminum Nitride (AlN) templates grown using mist chemical vapor deposition. From X-ray diffraction results, we observed that the (In x Ga1−x )2O3 thin films exhibited three different single-phase crystal structures depending on the value of x: orthorhombic (κ)-(In x Ga1−x )2O3 for x ≤ 0.186, hexagonal (hex)-(In x Ga1−x )2O3 for 0.409 ≤ x ≤ 0.634, and body-centered cubic (bcc)-(In x Ga1−x )2O3 for x ≥ 0.772. The optical bandgap of (In x Ga1−x )2O3 was tuned from 3.27 eV (bcc-In2O3) and 4.17 eV (hex-InGaO3) to 5.00 eV (κ-Ga2O3). Moreover, hex-(In x Ga1−x )2O3 exhibited a wide bandgap (4.30 eV) and a low resistivity (7.4×10‒1 Ω·cm). Furthermore, hex-(In x Ga1−x )2O3 thin films were successfully grown on GaN and AlGaN/GaN templates. Therefore, hex-(In x Ga1−x )2O3 can be used in transparent conductive films for deep-ultraviolet LEDs.

Controlled Alignment of Nanowires for Transparent Conductive Films: Methods and Applications

Background: Nanowires (NWs) have received extensive attention as the candidate materials for transparent conductive films (TCFs) in recent years. To date, the aligned nanowire (NW)-based TCFs with the same arrangement direction have shown superior characteristics to their random counterparts in applications. Objective: To fully develop the potential of NW TCFs in devices and provide inspiration for the development of subsequent NW alignment processes, this review summarizes state-of-the-art alignment techniques and emphasizes their mechanisms in detail from multiple perspectives. Methods: According to the mechanism of NW alignment, this review divides these techniques into seven categories, i.e., the assisted assembly of fluid flow, meniscus, pressure, template, electromagnetic field, contact and strain, and analyzes the characteristics of these techniques. Moreover, by briefly enumerating the applications of aligned NW films in solar cells, organic light-emitting diodes, and touch screens, the superiority of aligned NW films over random NW films is also addressed. Results: Contact-assisted assembly exhibits the best arrangement effect, reaching a 98.6% alignment degree within ±1°. Under the same conditions, shorter NWs show better alignment in several cases. The combination of various assembly techniques is also an effective means to improve the alignment effect. Conclusion: There is still room for improvement in the precise control of NW position, density and orientation in a simple, efficient and compatible process. Therefore, follow-up research work is needed to conquer these problems. Moreover, a process that can realize NW alignment and film patterning simultaneously is also a desirable scheme for fabricating personalized devices.

Novel Insights into Inkjet Printed Silver Nanowires Flexible Transparent Conductive Films

Silver nanowire (AgNWs) inks for inkjet printing were prepared and the effects of the solvent system, wetting agent, AgNWs suspension on the viscosity, surface tension, contact angle between ink droplet and poly(ethylene) terephthalate (PET) surface, and pH value of AgNWs ink were discussed. Further, AgNWs flexible transparent conductive films were fabricated by using inkjet printing process on the PET substrate, and the effects of the number printing layer, heat treatment temperature, drop frequency, and number of nozzle on the microstructures and photoelectric properties of AgNWs films were investigated in detail. The experimental results demonstrated that the 14-layer AgNWs printed film heated at 60 °C and 70 °C had an average sheet resistance of 13 Ω∙sq−1 and 23 Ω∙sq−1 and average transparency of 81.9% and 83.1%, respectively, and displayed good photoelectric performance when the inkjet printing parameters were set to the voltage of 20 V, number of nozzles of 16, drop frequency of 7000 Hz, droplet spacing of 15 μm, PET substrate temperatures of 40 °C and nozzles of 35 °C during printing, and heat treatment at 60 °C for 20 min. The accumulation and overflow of AgNWs at the edges of the linear pattern were observed, which resulted in a decrease in printing accuracy. We successfully printed the heart-shaped pattern and then demonstrated that it could work well. This showed that the well-defined pattern with good photoelectric properties can be obtained by using an inkjet printing process with silver nanowires ink as inkjet material.