By Debra Vogler, senior technical editor
February 7, 2011 -- ESI's PyroPhotonics Lasers introduced its 25-IR pulsed fiber laser for solar applications, e.g., scribing of thin film CIGS solar cells, about a year ago. In a podcast interview at Photonics West (January 22-27, 2011), Richard Murison, CTO and director of product marketing at ESI's recently acquired subsidiary, PyroPhotonics Lasers, described the laser's utility and functionality.
|Figure 1. A scribe line on a CIGS solar cell made using a mechanical scribing tool -- the standard industry process. SOURCE: ESI's PyroPhotonics|
Figure 2. A scribe line on a CIGS solar cell made using a conventional Q-switched laser that has a pulse width in the nanosecond range. The regions at the scribe edge indicate badly damaged CIGS material. SOURCE: ESI's PyroPhotonics
The pulse width can be programmed independently of the repetition rate and output power level from about 1ns to about 250ns or more; and the pulse shape can be programmed with 1ns resolution. "You can design a pulse shape that is quite distinct from a normal Q-switched pulse laser," said Murison. "For example, we can generate square temporal pulse shapes." Figures 1-4 illustrate scribe samples on CIGS material using different lasers.
|Figure 3. A scribe line on a CIGS solar cell made using a picosecond (i.e., ultra-fast; not Q-switched) laser. The CIGS region still shows some damage -- it wasn't eliminated. SOURCE: ESI's PyroPhotonics||Figure 4. A P2 scribe in CIGS using the PyroFlex 25-IR; there is no damage to the CIGS. SOURCE: SOURCE: ESI's PyroPhotonics|
In particular, the pulsed fiber laser can be used to scribe thin films. "By adjusting the pulse shape to a very precise configuration, we are able to scribe CIGS solar cells -- the P2 and the P3 processes -- that previously couldn't be done using nanosecond lasers," explained Murison. "The laser can also be used for c-Si solar cells, such as drilling holes for emitter wrap-through (EWT), selective emitter doping, laser-fired contacts, and other applications," noted Murison. The advantage of a flexible pulse laser, he notes, is that one platform can be used for many applications instead of needing a different one for each application.