Metallization optimization for high efficiency silicon heterojunction solar cells using low-temperature paste screen printing

An efficiency over 21% for silicon heterojunction solar cells has been successfully achieved in the RD line at AU Optronics (AUO). The performance improvement is stemmed from good passivation quality of thin film amorphous silicon layers, refined TCO formation, together with the optimized metallization process. In this paper, we focus on the progress of the screen printing technology using low-temperature conductive paste. Extensive efforts have been taken to reduce the serial resistance of the metallization. The trade off between front metal grid shading and resistance is also taken care of. We applied power loss calculation to optimize the metal contacts for a given TCO sheet resistance. AUO's new test run shows more than 2.8% reduction of power loss, which equals 0.64% absolute efficiency gain compared to our old test run.