Partially contacted surfaces with contact size in the 1 μm range for c-Si PERC solar cells

We examine the electrical benefits of creating contacts with sizes in the 1 μm range on partially contacted surfaces for c-Si PERC/L solar cells. In such a design, a dielectric layer that provides surface passivation is periodically opened to create contacts. Analytical models demonstrate that small contacts in the 1 μm range and separated by a few microns result in lower ohmic losses when compared to a typical contact configuration. In order to obtain a good surface passivation quality, surface recombination velocities below 10
³
cm/s are needed for the contacted area. From PC-1D simulations of a reference structure, a clear advantage for small contacts is deduced for surface recombination at the contacts in the 10
²
-10
⁵
cm/s range. Additionally, a fabrication process to achieve the desired contact configuration is described using Al
₂
O
₃
and thermally grown SiO
₂
films. This process is based on colloidal lithography using polystyrene nanoparticles. For Al
₂
O
₃
films, an incomplete contact opening is observed, while much more repeatable results are obtained for SiO
₂
films.