In this study, two-dimensional (2D) computer simulations of the n+pn+ emitter-wrap-through (EWT) cell structure with industrially relevant parameters is performed and a comparison is made with p-type substrate interdigitated back contact (IBC) cells.

Simulation results show that the EWT cell is particularly suited for low bulk lifetimes and thin substrates. Simulation results also indicate that achieving a lifetime of around 45 ?s will be sufficient to realize very high-efficiency EWT cells. The EWT cell shows much higher robustness to poor material lifetime as well as surface passivation compared to the IBC cell.

While a 1 ms lifetime IBC cell drops to efficiencies less than 14.5% for an intrinsic surface recombination velocity (SRV) of 10,000 cm/s, the EWT cell can maintain efficiencies above 15% at a much lower bulk lifetime of 30 ?s and higher SRV of 300,000 cm/s.

By Mohamed M. Hilali, Peter Hacke, and James M. Gee, Advent Solar, Inc.