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Awards vFinal DR 18/12/09 09:36 Page 33
Thin Film Innovation Award
TCO 1200 System
The Oerlikon Solar TCO 1200 is a fully
automated high volume system for the
deposition of a novel and adjustable
Transparent Conductive Oxide (TCO) film. The
TCO 1200 process technology allows
adjustment of film morphology and conductivity
to match ideal parameters for the PV absorber
stack while utilizing an innovative ZnOx film
composition with superior light trapping versus
standard SnOx films.
TCO films have been used within thin film PV doping gas delivery. These features allow the
panels since the beginning of the technology. film to be adjusted to optimize panel power
The TCO film needs to: allow full spectrum light output.
onto the panel for generation of energy by the
PV absorber, act as a current collector and act In order to develop the next generation thin film
as a light scattering and trapping layer which silicon PV cells, light trapping by advanced TCO
forces key wavelengths to traverse the PV is essential. The new LPCVD process from
absorber stack for multiple reflections, Oerlikon Solar has demonstrated higher light
increasing the chance for the light to create trapping abilities. This is especially important for
electricity. The standard technology for micromorph solar cells where the absorber
deposition of TCO films has been sputtering. layers are engineered to be as thin as possible
Issue VI 2009
Unfortunately the sputtering process allows only while keeping the efficiency high. In addition,
a small window of process adjustment and no amorphous silicon single junction cells have an
optimization of material composition or light enhanced susceptibility to Staebler-Wronski
scattering. Another popular approach to TCO degradation, so efficient light management
fabrication, especially by glass manufacturers, allows a reduction in layer thickness,
is Atmospheric Pressure CVD (APCVD). APCVD fundamental for high performance in these
techniques typically require very high material systems.
deposition temperatures, >500° C, and so
forces the films to be applied to the glass The output current of an Oerlikon Solar TCO
directly without any PV absorber films present. film is significantly higher than a high quality
commercial APCVD film, accounting for an
This is possible only for the first film on glass at additional 0.5% improvement in stabilized
the beginning of module manufacture, however, efficiency. The TCO 1200 LPCVD manufacturing
the back contact TCO film cannot be deposited system allows in a single layer to optimize a
by APCVD. The TCO 1200 LPCVD (Low tandem absorber stack with very high haze light
Pressure Chemical Vapor Deposition) reactor scattering, very low sheet resistance and
has several new hardware and chemistry excellent transmission characteristics. Also, the
innovations, allowing a fast and highly uniform low temperature nature of the deposition allows
IR camera controlled heating, a low temperature this same TCO layer to be used successfully for
process (›200° C) and controllable conductivity the TCO back contact, again increasing light
and crystal morphology through adjustable trapping within the cell.
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