Laser-induced defects in laser-grooved silicon solar cells

Abstract

Silicon laser-grooved solar cells are now replacing screen-printed solar cells in the global market. The Olympic village in Sydney will be the first such village to be powered by these solar cells with a total output of 650 kW. Burying the metal contacts allows for a reduction in shading losses and an increase in blue-light response due to lower front-surface recombination velocities. The efficiency of these cells, however, still exceeded expectations. Gettering from laser-induced damage sites was believed to enhance cell performance alhtough there was no hard evidence for this. Initial attempts to reveal these defects mistook S-pits for dislocations. This paper studies the nature of laser-induced damage revealing dislocations localized along the grooves for the first time. An understanding of these effects have improved the rear surface design of laser grooved solar cells. However, efforts to improve cell efficiency by using a bi-facial structure have been hampered by these defects. The spreading of the junction along them can also explain the much better cell performance laser-grooved solar cells.