Wenfeng Shen

Highly flexible and transparent film heaters based on polyimide films embedded with silver nanowires

Highly flexible and transparent film heaters (TFHs) with superior mechanical and thermal stability were fabricated by embedding silver nanowires (AgNWs) into transparent polyimide (PI) films using a solution coating method. The fabricated AgNW/PI hybrid TFHs exhibited higher heating temperatures (∼96 °C) with lower input voltage (∼6 V), shorter response time (T < 40 s), and lower power consumption (160.6 °C cm2 W−1) than ITO/FTO heaters, as well as stability after repeated use. The AgNW/PI hybrid TFHs also showed excellent resistance to bending. After undergoing outer bending for a 1000 times, the change of sheet resistance was less than 18%. The effective embedment of the AgNW network in the surface of the transparent PI film not only decreased the surface roughness (Rrms < 1 nm) but also enhanced the resistance against oxidation and moisture. Potential applications of the AgNW/PI TFHs in window defogging and thermochromics are demonstrated.

Highly Thermostable, Flexible, Transparent, and Conductive Films on Polyimide Substrate with an AZO/AgNW/AZO Structure

Flexible transparent conductive films (TCFs) are used in a variety of optoelectronic devices. However, their use is limited due to poor thermostability. We report hybrid TCFs incorporation in both aluminum-doped zinc oxide (AZO) and silver nanowires (AgNWs). The layered AZO/AgNWs/AZO structure was deposited onto a transparent polyimide (PI) substrate and displayed excellent thermostability. When heated to 250 °C for 1 h, the change in resistivity (Rc) was less than 10% (Rc of pure AgNW film > 500) while retaining good photoelectric properties (Rsh = 8.6 Ohm/sq and T = 74.4%). Layering the AgNW network between AZO films decreased the surface roughness (Rrms < 8 nm) and enhances the mechanical flexibility of the hybrid films. The combination of these characteristics makes the hybrid film an excellent candidate for substrates of novel flexible optoelectronic devices which require high-temperature processing.

Flexible transparent conductive films on PET substrates with an AZO/AgNW/AZO sandwich structure

Hybrid transparent conductive films (TCFs) with a sandwich structure composed of aluminum-doped zinc oxide (AZO) and Ag nanowires (AgNWs) were deposited on polyethylene terephthalate (PET) substrates. The AZO layers were prepared at room temperature by RF magnetron sputtering. The AgNWs were synthesized by a modified polyol method and inserted into the AZO layers. The optical properties and conductivity can be modified by the number of spin-coating cycles of an AgNWs suspension. Typically, an AZO/AgNW/AZO hybrid film exhibited an optical transmittance of 80.5%, a sheet resistance of 27.6 Ω sq−1 and an optical haze of 14.9%. The increase in optical haze caused by the silver nanowires may be beneficial for applications in solar cells. The hybrid films presented excellent flexible stability, showing only minor resistance changes and no surface cracks compared with pure AZO films. The AZO layers acted as the protecting layers that enhanced the adhesive and thermal stability of the hybrid films. The resulting hybrid TCFs with an AZO/AgNW/AZO sandwich structure show potential applications in flexible electronics, energy storage and photovoltaic devices.

Surfactant-free hydrothermal synthesis and sensitivity characterization of Pd-doped SnO 2 nanocrystals on multiwalled carbon nanotubes

In the present study, a simple approach has been presented to in situ deposition of Pd-doped well-crystallized SnO2 nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution of SnCl2. The morphology, microstructure and surface chemistry of the as-prepared nanocomposites were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The HRTEM and XRD results show that the well-crystallized SnO2 nanocrystals with uniform crystal size (about 5 nm) tightly and homogenously coat on the entire surface of the MWCNTs. The carboxylic function groups on the MWCNTs surface may supply nucleation sites for facilitating the in situ deposition of SnO2 nanocrystals. The XPS results reveal that the chemical states of the nanocomposites and the dopant of Pd mainly exists in two chemical states as Pd2+ and Pd4+. The response of the 2.5 at% Pd-doped SnO2/MWCNTs nanocomposites to 1000 ppm NO at the temperature of 250 °C behaviors better, whose response time is about 70 s and the sensitivity is about 4.62.

Preparation and cold welding of silver nanowire based transparent electrodes with optical transmittances >90% and sheet resistances <10 ohm/sq

In this article, silver nanowires (AgNWs) with aspect ratios of 1000 and lengths up to 200 μm are obtained by a modified polyol approach. These very long AgNWs are then utilized to prepare transparent electrodes (TEs) displaying a transmittance of 91.3% at a sheet resistance of 8.6 ohm/sq without any post-treatment. Furthermore, we also demonstrate a process for the cold welding of Ag NWs by simply dipping the AgNWs films into CTAB solutions, resulting in a further improvement for the optoelectronic performance. After the post-treatment, the AgNW-based TEs can achieve a transmittance of 93% at a sheet resistance of 9.5 ohm/sq. In addition, the electric behaviors of AgNW-based TEs are investigated. In the bulk-like regime, for the as-prepared AgNW-based TEs, the Figure of merit (FOM), DC to optical conductivity ratio reaches up to 566.8. After the cold welding process, the DC to optical conductivity ratio can reach even higher values (631.6). In the percolative regime, the as-prepared and welded AgNW-based TEs can achieve Π (FOM with percolative-like behavior) values of 166.8 and 242.1, respectively.

Fabrication of High-Haze Flexible Transparent Conductive PMMA Films Embedded with Silver Nanowires*

High-haze flexible transparent conductive polymethyl methacrylate (PMMA) films embedded with silver nanowires (AgNWs) are fabricated by a low-cost and simple process. The volatilization rate of the solvent in PMMA solution affects the surface microstructures and morphologies, which results in different haze factors of the composite films. The areal mass density of AgNW shows a significant influence on the optical and electrical properties of composite films. The AgNW/PMMA transparent conductive films with the sheet resistance of 5.5Ωsq −1 exhibit an excellent performance with a high haze factor of 81.0% at 550 nm.

Application of inkjet printing technology in solar cell fabrication

With the increasing energy demand and consumption, the development and utilization of new energy have drawn much attention. Solar cell is a device which can convert sunlight energy into electricity by the photovoltaic effect, and solar cell has become a popular research project. Various printing techniques have been adopted in the fabrication of solar cell. Due to the unique advantages such as high material utilization rate, low cost, flexible, noncontact process and digital patterning, inkjet printing is believed to be the next generation solar cell manufacturing technology. The structure of solar cell and the recent progress in the application of inkjet printing technology in solar cell fabrication is reviewed. Detailed introductions to the application in metal electrode, transparent conductors and absorber layer of solar cell are presented. The potential and promising trends of inkjet printing technology in solar cell fabrication are also proposed. Inkjet printing technology will be an extremely important tool in solar cell fabrication in the near future.