Processing sequence of the cells. Eight solar cell batches are prepared. Gra. denotes the cells on graphite substrate and Waf. denotes the cells on wafers as reference. Laser edge isolation (LEI), laser single side contact (LSSC) and hydrogen bulk passivation (H⁺ pass.) were applied in the cell process. Batches Gra. A–C on graphite substrates, reference batches Waf. A–C on Si wafers with the same processing after ZMR as Gra. A–C.