The new process is based on silver nanoparticle films and the use of intense pulsed light to create conductive nanoparticles. Studies carried out at Oregon State University’s College of Engineering have found there is a relationship between film temperature and densification. This is important because densification increases the density of a nanoparticle thin-film and these means improved electrical conductivity.
By modifying the technique, the researchers found that varying temperature improves performance without the need to alter the pulse energy. Speaking with Controlled Environments, the lead researcher Professor Rajiv Malhotra explains: “For some applications we want to have maximum density possible. For some we don’t. Thus, it becomes important to control the densification of the material.”
The key aspect is also with controlling the combination of fluence and pulses. The research found that a smaller number of high-fluence pulses rapidly produces high density (radiant fluence is the radiant energy received by a surface per unit area); and for greater density control, a larger number of low-fluence pulses is required.
These variations lead to improved process control and equipment design. Moreover, not only does the new process lead to improved conductivity, it also paves the way for a faster production process. The new process is also rapid; taking only a few seconds to complete and it can process a large area of material in one go.
For standard material, a temperature of 120 degrees Celsius and a time of two seconds appears optimal. The previous process required a temperature of 250 degrees Celsius and a time of 20 seconds. Importantly the lower temperature is critical for flexible electronics. Flexible electronics are printed onto paper or plastics, which allow devices to be bent or folded, and these substances cannot survive higher temperatures without damage.
The types of applications the pulsed light can be used for includes printed electronics, solar cells, gas sensing and photocatalysis. These can be used in radiofrequency identification tags, various flexible electronics, and wearable biomedical sensors.
The research is published in the journal Nanotechnology, with the paper headed “The Coupling Between Densification and Optical Heating in Intense Pulsed Light Sintering of Silver Nanoparticles.”
