Tis report details the results a novel doping method called Laser Chemical Processing (LCP) so it can be used in the production of high efficiency, low cost cells.
In Laser Chemical Processing (LCP) technology, a liquid jet with a typical width of that of a human hair is formed by pumping liquid through specially shaped nozzles under high pressure. A laser beam is guided within the liquid jet and used to fabricate the contact regions of solar cells. This project addressed key challenges in LCP technology that created significant hurdles to its commercial application, particularly the laser beam size and uniformity when it reaches the solar cell. Typically, the beam intensity is highly non-uniform.
In addition, the beam size is equal to the size of the liquid jet. To overcome these limitations, the optics of the laser beam was studied in detail and the way in which the laser beam is introduced into the beam was radically modified. By using advanced techniques to couple the laser beam into the liquid jet, it was possible to obtain a much smaller beam size. The excellent quality of the contact regions that can be realised from the modified process were demonstrated using different measurement techniques. To demonstrate the full potential of the advanced LCP technology, solar cells were fabricated using LCP technology for both solar cell contacts. In a first attempt with not yet optimised processing parameters, a conversion efficiency of 20.4% was realised, significantly higher than the efficiency of most currently produced commercial solar cells. This result confirms the excellent properties obtained from the advanced LCP process and means that significant hurdles to the commercial application of LCP technology for solar cell fabrication have been addressed.