Subject number:

							Subject number:         2 – Crystalline Silicon Solar Cells and Materials Technology, 2.2 - Mono- and
                        Multicrystalline Silicon Cells and Materials, Processing Technology of Wafers,
                        Sheets and Ribbons
Full title:           Investigation of the laser diffused from spin-on glass localized point
                      contacts
Authors:              Loreta Meslinaitė, Julius Janušonis, Algirdas Galdikas, Juras Ulbikas
Corresponding author: Loreta Meslinaite, e-mail: loretoss@gmail.com
Affiliations:         a) Applied Research Institute for Prospective Technologies, Galvydzio 5,
                      LT-08236, Vilnius, Lithuania

Purpose of the work, scientific innovation and relevance
Local point contacts were introduced several decades ago in the PERL (passivated emitter rear
locally diffused) and PERC solar cell designs. They offer several advantages – the reduced
saturation current and increased voltage, low bow which is very important for the thin wafers and
also good rear side reflectivity properties.
In this work we propose a different rear local contact formation method, which is applied in our
new solar cell production scheme.

Approach
The localized point contacts with the local BSF were manufactured using the laser assisted
diffusion from the spin-on glass source. This spin-on glass also acts as the passivating layer
which is used to reduce the metal/semiconductor contact area.
The boron glass was spun-on on the rear surface of the cell. Afterwards local laser assisted
diffusion was performed together with the boron glass ablation to ensure the good local BSF
properties and low contact resistance. Thus the local point contacts with boron diffusion
underneath are formed.
Various regimes of the process were tested, the passivation properties of the layer were optimized
and the influence of the temperature treatment prior to the local contact formation was
investigated.
The theoretical optimization was performed searching for the optimal laser diffusion parameters
and point contact grid geometry.

Results and conclusions
The new type of the local point contacts with a boron local BSF was manufactured and
investigated using local laser induced diffusion and subsequent ablation. The theoretical
optimization of the process and the point contact grid was performed.