Rapid thermal firing of screen printed contacts for large area crystalline silicon solar cells

Rapid thermal firing (RTF), i.e. firing of screen printed contacts using rapid thermal processing (RTP), is a promising alternative compared to infrared heated conveyor belt furnaces concerning a reduction in process time. In addition, due to flexible process design and in-situ temperature measurement, RTF is well suited for detailed studies and optimisation of the firing process and the contact formation. Exploiting the advantages of RTP such as high heating and cooling rates and short plateau times, the authors have developed an RTF process with a very short total process time of 60 s and less than 10 s above 600/spl deg/C. Applying the process to large area cells (100 cm/sup 2/) fill factors >78% have been achieved even on shallow RTP-diffused emitters with a grid shading of 7%. Contact resistivity mappings of the rapid thermal fired front contact grid confirm a laterally homogeneous contact formation.