Comparative Models of Induced Thermomechanical Stress in Silicon Solar Cells Interconnected with Conventional Tabbing and Wire-Based Interconnection Methods

Induced thermomechanical stress in interconnected Si solar cells can pre-dispose cells to microcrack formation which can degrade module performance in the field. This paper reports on the results of finite element simulations of thermomechanical stress induced in Si monocrystalline wafers when solar cells are interconnected by conventional ribbon tabbing, multi-busbar (MBB) and Smartwire Connection Technology (SWCT). Simulations were performed to determine where thermomechanical stress is induced in the Si wafers and to compare the magnitude of the induced stress with the different interconnection methods. It is shown that the induced Si stress depends on the ribbon shape and cross-sectional area with Si stress decreasing with decreased cross-sectional area and increasing ribbon width (for constant cross-sectional area). Furthermore, the advantages of the smaller wire cross-sectional area used in MBB and low-temperature solder used in SWCT, compared to conventional tabbing, were offset by the reduced contact area between the wires and the solar cells.