Page 84 - Applied Photovoltaics

x 20% efficient large area solar cells and 18% efficient modules have been
demonstrated, compared with about 14% and 11% typically achieved using
screen printing technology

Figure 4.16. Cross-section of Laser Grooved Buried Contact Solar Cell.

Additional advantages for use as concentrator cells include (Wohlgemuth &
Narayanan, 1991):
x higher efficiencies achievable on lower cost multicrystalline or single crystal
substrates
x lower cost plated nickel-copper metallisation can be used
x process is self-aligning
x deeper diffusion in grooves provides good screening of metal from emitter,
while allowing for a lightly-doped, higher efficiency emitter
x avoidance of top surface ‘dead layer’ through the use of lightly-doped emitter
that gives significantly improved response to short wavelength light
x reduced contact resistance resulting from large plated wall area and heavily
doped contact region.
The production sequence for laser grooved buried contact solar cells is as follows:
1. Texturing of surfaces.

2. Phosphorus diffusion and oxidation of the surfaces.
3. Laser scribing to form the grooves.

4. Chemical cleaning.
5. Heavy phosphorus diffusion of the groove walls.

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