Study on the influence of the Cu ribbon detachment ratio on the electrical characteristics of photovoltaic modules

Abstract Based on the carrier transport path at the welding interface of a Cu ribbon, this study proposes a theoretical model of the Cu ribbon detachment ratio (DR) and the busbar resistance, Cu ribbon resistance, and contact resistance. The relationship between the Cu ribbon DR and the resistance of each welding layer, as well as the relative contribution of the resistance of each welding layer to the series resistance, is analyzed using the designed theoretical model. The results show that with the increase in the DR value, both the busbar resistance and contact resistance increase exponentially, whereas the Cu ribbon resistance decreases linearly. The effects of the busbar resistance, Cu ribbon resistance, and contact resistance on the series resistance are 36.22%, 0.40% and 63.38%, respectively. The results also indicate that series resistance is mainly affected by the busbar resistance and contact resistance. The maximum value of the Cu ribbon detachment was quantitatively calculated, when the DR value is larger than 93%, the detachment of the Cu ribbon can make a photovoltaic (PV) module retired. In this study, PV modules with Cu ribbons having different DR values are fabricated and tested in the laboratory. The results show that the maximum relative errors of the series resistance, fill factor, and output power of the values calculated by the proposed model and experimental test values are 4.77%, 1.05% and 1.40%, respectively. This verifies the feasibility of the proposed theoretical model. Finally, based on the relative contribution of the resistance of each welding layer to the series resistance, this study designs a B-type PV module with a thick-busbar and short-welding Cu ribbon. The results show that the electrical performance of the B-type PV module with a busbar thickness of 30 μ m a welding length of the Cu ribbon of 70% performs.