2D-Modeling and Development of Interdigitated Back Contact Solar Cells on Low-Cost Substrates

Presented at the 4th World Conference on Photovoltaic Energy Conversion; Hawaii, USA; May 7-12, 2006.Two-dimensional numerical simulations were performed to derive design rules for low-cost, high-efficiency interdigitated back contact (IBC) solar cells on a low-cost substrate. The IBC solar cells were designed to be fabricated using either the conventional screen printing or photolithography metallization processes. Bulk lifetime, bulk resistivity, contact spacing (pitch), contact opening width, recombination in the gap between the p(+) BSF and n(+) emitter, and the ratio of emitter width to pitch have been used as key variables in the simulations. It is found that short circuit current density (J(sc)) is not only a strong function of the bulk lifetime but also the emitter coverage of the rear surface. Fill factor (FF) decreases as the emitter coverage increases because the majority carriers need to travel a longer distance through the substrate for longer emitter width. The simulated IBC results were compared with those for conventional screen printed solar cells. It was found that the IBC solar cell outperforms the screen printed (SP) solar cell when the bulk lifetime is above 50 μs due to higher V(oc) and J(sc), which suggests that higher performance can be realized on low-cost substrates with the IBC structure