By Robby Peibst, Institute for Solar Energy Research Hamelin (ISFH); Agnes Merkle, Institute for Solar Energy Research Hamelin (ISFH); Udo Römer, Institute for Solar Energy Research Hamelin (ISFH); Bianca Lim, Institute for Solar Energy Research Hamelin (ISFH); Yevgeniya Larionova, Research Scientist, Institute for Solar Energy Research Hamelin (ISFH); Rolf Brendel, Scientific Director, Institute for Solar Energy Research Hamelin (ISFH); Jan Krügener, Associate Researcher, Institute of Electronic Materials and Devices; Eberhard Bugiel, Institute of Electronic Materials and Devices; Manav Sheoran, Team Leader, Applied Materials; John Graff, Director of Solar Cell Technology, Applied Materials
Ion implantation offers significant process simplification potential for the fabrication of back-junction back-contact (BJBC) solar cells. First, the number of high-temperature steps can be reduced to one when applying a co-annealing process which includes an in situ growth of a silicon oxide passivation layer. Second, the implanted regions can be patterned in situ by utilizing shadow masks. ISFH's results from evaluating both aspects are reported in this paper. With fully ion-implanted, co-annealed and laser-structured small- area cells, efficiencies of up to 23.41% (20mm x 20mm designated area) have now been achieved. It is shown that the excellent recombination behaviour of 156mm x 156mm BJBC cells patterned in situ implies a potential for realizing efficiencies greater than 23%; however, back-end issues have so far limited the efficiency to 22.1% (full-area measurement). Ion implantation can also be utilized for the doping of BJBC cells with carrier-selective junctions based on polycrystalline silicon. The current status of ISFH's work in this direction is presented.
