-
This paper presents ISFH’s recent developments and advances in the field of back-contacted silicon solar cells. The efficiency potential of back-contacted solar cells is very high; nevertheless, in industrial production, back-contacted solar cells are decidedly the minority. In the field of back-contacted solar cells, ISFH has developed several cell concepts and new processing techniques, such as laser ablation for silicon structuring, contact opening through passivation layers, and hole drilling for emitter-wrap-through (EWT) solar cells. The latest results are presented regarding ISFH’s work on back-junction back-contacted solar cells and EWT solar cells, as well as on back-contacted solar cells employing an amorphous/crystalline silicon heterojunction. Also discussed are the advances in high-throughput evaporation of aluminium as a low-cost option for the metallization of back-contacted solar cells. Finally, a novel, silver-free cell interconnection technique is presented, which is based on the direct laser welding of a highly conductive, low-cost Al foil, as a cell interconnect, onto the rear side of back-contacted solar cells.
-
This paper reviews metal wrap through (MWT) solar cell and module technology. As MWT solar cells and modules have received more and more attention in recent years, many highly efficient MWT cell types have been presented by research institutes and industry and are summarized herein. The MWT cell structure benefits from a reduced silver consumption compared with a conventional H-pattern cell, and its realization can be easily combined with novel metallization technologies such as dispensing or stencil printing. The introduction of a rear-surface passivation into the MWT structure is feasible with the high-performance MWT (HIP-MWT) concept developed at Fraunhofer ISE. The resulting fabrication sequence includes only one additional process step – laser drilling of vias – compared with an H-pattern passivated emitter and rear cell (PERC). Furthermore, the synergistic effects of MWT and PERC boost the conversion efficiency gain of MWT-PERC-type cells beyond the expected sum of what could be achieved individually from these two approaches. According to the calculations made by Fraunhofer ISE, conversion efficiencies of up to 21.5% (annealed) are feasible for p-type Cz silicon MWT-PERC cells. Because via metallization is one of the challenges in the fabrication of MWT cells, different via pastes are investigated with regard to their series resistance and contact behaviour. With cell-to-module losses in conversion efficiency of only 0.9% abs., both the interconnector-based MWT module technology and the conductive backsheet concept show promising results.
-
-
-
-
