Rapid metallization paste firing of crystalline silicon solar cells

Co-firing of crystalline silicon solar cell metal contacts in infrared conveyor furnaces is the standard of the industry today. Typical ramp rates of 60-80°C./s. and total firing times of approximately 16 to 20 seconds are used due to limitations inherent in currently available production equipment. We report on a novel industrial-scale process utilizing ramp rates as high as 400°C./s. and high cooling rates which result in total firing times of 1.09 to 1.72 seconds. Cells have been produced with this process with measured fill factors in excess of 80% and high shunt resistance. At the lower firing times in this experimental series, high fill factors were maintained but open circuit voltage (Voc) reduced indicating non-optimal back surface field (BSF) formation. This study addresses the requirements for aluminum BSF formation in very rapid co-firing.