One researcher's interest was in the development of fabrics incorporating integrated illuminators. Unfortunately, the fabric itself does not serve as a suitable surface for the luminescent material. However, a team of scientists has found a way to solve this problem by using a new technology called illuminator fibers to integrate the illuminators directly into the fabric.
The research team from China developed polymer light-emitting electrochemical cells (PLECs). Like many other illuminating devices, PLECs have two metal electrodes that are connected to an organic thin layer that is a semiconductor. Because PLECs incorporate moving ions into the semiconductor, they have many advantages over other light-emitting diodes (LEDs): low operating voltage, high photoelectric conversion efficiency, and high power efficiency. PLECs are a good choice because they do not require the use of air sensitive metals and can be used on rough surfaces. These characteristics make it suitable for mass production.
These fibrous PLECs have a four-layer coaxial structure. The PLEC fiber is prepared by a solution method, firstly using steel wire as a matrix of the fiber, followed by dip coating a thin layer of ZnO nanoparticles. This layer has two main functions: to protect the next luminescent layer while reducing leakage current and improving current efficiency.
Next, a layer of electroluminescent polymer is deposited on the surface of the wire using a dipping process. Finally, a neatly arranged carbon nanotube layer is wrapped around the outermost layer of the wire bundle, wherein the carbon nanotubes are dry drawn spun carbon nanotubes. Since the carbon nanotube structures are highly uniform, they provide high electrical conductivity to the fibers. The photo shows a uniform fiber diameter and a smooth outer surface.
Scientists who created these fibers studied the life of these devices. They found that the fiber gradually glowed within 21 minutes and gradually dimmed within four hours; in this study, the light from the fiber was blue. When a voltage of 5.6 V was applied, the fiber was lighted; when the applied voltage was 13 V, the fiber current intensity peaked. When the fiber is pre-charged, it shows a fast turn-on response similar to a conventional LED.
The brightness of the light emitted by the fiber is almost completely unaffected by the viewing angle. Even if the fiber is bent, it can maintain a brightness higher than 90% without significant damage. Although only blue was studied in this exploration, the research team believes that other colors have similar effects.
Taken together, these luminescent fibers can be woven into the fabric without compromising its luminescent properties.
