Large area, screen printed silicon solar cells with selective emitter made by laser overdoping and RTA spin-on glasses

In this paper, the authors describe their work on a new solar cells fabrication process, based on the use of rapid thermal diffusion (RTD) from spin-on techniques, laser assisted treatments to get selective emitter structures and screen-printing. The homogeneous lightly doped emitter is first made by rapid thermal diffusion from a P-doped spin-on glass (SOG) film. Laser overdoping of contact regions follows, to form the selective emitter structure, by writing the grid pattern using a laser beam. Finally, screen-printing is used to obtain the contacts; proper solutions have been developed for optical realignment to the laser pattern, with a resolution of about 10 microns. The authors have prepared several batches of small area solar cells, made by using these processes separately, with the aim of studying the influence of the main laser and dopant parameters on solar cell performances. A further step has been to use all the processes together. Large area device preparation is in progress.