Numerical Simulation and Modeling of Resistive and Recombination Losses in MWT Solar Cells

This study analyzes the impact of resistive and recombination losses in metal wrap through (MWT) solar cells through technology computer aided design (TCAD) numerical simulations. Two types of MWT architectures are considered in this study: “point busbar,” featuring one circular tabbing contact for each via at the back side, and “continuous busbar,” in which the rear busbar connects all the vias along a line. A comparison with conventional, H-pattern, front contact (FC) solar cells is performed by adopting the surface recombination velocity at the rear-contact isolation region as a parameter representative of possible passivation options. The differences under dark and light conditions are highlighted. Moreover, the following resistive losses in MWT cells are investigated: via resistance, shunting effect, and lateral conduction of charge carriers above rear busbar. An analytical model to account for the lateral conduction of charge carriers is proposed and validated by means of numerical simulations. While the advantage of MWT over FC cells is confirmed by simulation, we quantitatively show how the resistive and recombination losses limit the efficiency of MWT cells.