David H. Meakin

Busbarless emitter wrap-through solar cells and modules

Back-contact crystalline-silicon photovoltaic solar cells and modules offer a number of advantages including the elimination of grid shadowing losses, reduced cost by use of thinner silicon substrates, simpler module assembly, and improved aesthetics. While the existing method for interconnecting and stringing edge-connected back contact cells is acceptably straight-forward and reliable, there are further gains to be exploited when you have both contact polarities on one side of the cell. In this work, we produce ‘busbarless’ emitter wrap-through (EWT) solar cells that use about 65% less gridline Ag metallization mass compared to the edge tab design. Further, series resistance power losses are reduced by extraction of current from more places on the cell rear leading to a fill factor improvement of about 6% (relative) on the module level. Series resistance and current-generation losses associated with large rear bondpads and bus bars are eliminated. Use of thin Si wafers is enabled because of the reduced Ag metallization mass and by interconnection with conductive adhesives leading to reduced bow. The busbarless cell design interconnected with conductive adhesives passes International Electrotechnical Commission damp heat and thermal cycling tests.

Development of commercial-scale photovoltaic modules using monolithic module assembly

Back-contact silicon solar cells enable new concepts for the module design and assembly. Monolithic module assembly refers to a process whereby the solar cell circuit and the module encapsulation are accomplished during the lamination step. This paper describes the advantages of MMA, progress in design and qualification of a commercial module based on MMA, and first results on pilot-scale production of MMA modules. Photovoltaic modules are expected to have 25-year lifetimes. Hence, an extensive program for reliability testing and verification was instituted in order to help accelerate fundamental understanding of long-term performance characteristics.