Abstract:
This work aims at inspecting the device operation and performance of a novel flipped npn
microstructure solar cell based on low-cost heavily doped silicon wafers. The flipped structure was
designed to eliminate the shadowing effect as applied in the conventional silicon-based interdigitated
back-contact cell (IBC). Due to the disappearance of the shadowing impact, the optical performance
and short-circuit current density of the structure have been improved. Accordingly, the cell power
conversion efficiency (PCE) has been improved in comparison to the conventional npn solar cell
microstructure. A detailed analysis of the flipped npn structure was carried out in which we per-
formed TCAD simulations for the electrical and optical performance of the flipped cell. Additionally,
a comparison between the presented flipped microstructure and the conventional npn solar cell
was accomplished. The PCE of the conventional npn structure was found to be 14.5%, while it was
about 15% for the flipped structure when using the same cell physical parameters. Furthermore, the
surface recombination velocity and base bulk lifetime, which are the most important recombination
parameters, were studied to investigate their influence on the flipped microstructure performance.
An efficiency of up to 16% could be reached when some design parameters were properly fine-tuned.
Moreover, the impact of the different physical models on the performance of the proposed cell was
studied, and it was revealed that band gap narrowing effect was the most significant factor limiting
the open-circuit voltage. All the simulations accomplished in this analysis were carried out using the
SILVACO TCAD process and device simulators.
