Investigation of single step Co-anneal of ion implanted boron and phosphorous to fabricate N-type front junction solar cells

This paper reports on the fabrication of n-type front junction cells by co-annealing of Boron emitter and Phosphorous back surface field (BSF) implanted with a beam line ion implantation tool. In contrast to other techniques such as BBR₃, BCL₃, or even ion implantation which generally use two separate anneals to form the emitter and the BSF, we have investigated the use of a single anneal to form ion implanted emitter and BSF simultaneously. Several anneal conditions were investigated in the experiment, and efficiency of 19.5% was obtained for N-type 239 cm² Cz front junction structure. For every condition, we also studied the bulk lifetime and dark saturation current densities, including Joe (emitter) and Job´ (BSF), to understand the enhancements and shortcomings of the device and provide guidelines for higher efficiency.