A simple processing sequence for selective emitters [Si solar cells]

A novel method to form selective emitters in only one diffusion step without etching or masking steps has been recently introduced for Si solar cells. A phosphorous containing doping source is applied selectively to the front side of a p-type crystalline Si substrate in the form of a paste and subsequently dried. The print is performed with advanced screen printing equipment that allows very precise positioning. In only one diffusion step, deeply diffused regions form under the printed doping source. At the same time, the adjacent regions become weaker doped by P atoms diffusing indirectly from the printed source through the gas ambient into those regions that were not covered by the P paste. The advantages of such a processing sequence over typical industrial processes are addressed. Results from an ongoing optimisation of such a sequence are given and interpreted