We present a detailed study on aluminum-boron doping profiles formed in silicon by alloying from screen-printed aluminum pastes containing boron additives. We show that an increase in the effective peak temperature T peak,eff (determined from phase diagram calculations) of the alloying process leads to higher concentrations of both Al and B atoms within the alloyed p+ region, resulting in (i) higher potential barriers for electrons, but also (ii) increased densities of recombination-active Al defects. While the improved potential barrier predominates for Tpeak,eff â‰ 770 C, the increased defect density prevails for T peak,eff â‰ 800 C, thus defining an optimal effective peak temperature. Furthermore, we show that, by increasing the amount of elemental B added to the paste, the acceptor concentration can be increased without affecting the defect density. Therefore, the optimal printing and firing conditions comprise high B amounts and low, adapted effective peak temperatures. For a B content of 0.9 wt% and Tpeak,eff = 765 C, we have achieved a saturation current density of 253 fA/cm2, corresponding to an implied open-circuit voltage of 665 mV, which demonstrates the high potential of B additives within Al pastes to further improve the efficiency of Si solar cells with Al-alloyed p+ rear. © 2013 The Authors.
Rauer, M., Schmiga, C., Tuschinsky, A., Glatthaar, M., & Glunz, S. W. (2013). Investigation of aluminum-boron doping profiles formed by coalloying from screen-printed pastes. In Energy Procedia (Vol. 43, pp. 93–99). https://doi.org/10.1016/j.egypro.2013.11.093