SOLARAWARDS2011 SHORTLISTED
Customer Benefits
3M Solar Mirror Film 1100 enables greater design flexibility than standard glass, allowing for larger geometry reflectors than previously possible. The lightweight, large-area assemblies possible with Solar Mirror Film 1100 have the potential to reduce the total installed cost of CSP systems by more than 15 %. Additionally, reflective film-based reflectors are up to 75 % lighter than glass mirrors, significantly reducing transportation costs while easing the installation process.
be increased significantly and the process time could be reduced, which allows a higher throughput and leads to a lower total chemical consumption. A positive side-effect is the fact that the lower consumptions cause less impact on the environment.
of the cells. Another big advantage of GP ALKA-TEX .Plus is that the number of recipes for different wafer qualities can be reduced to a basic recipe.
GP Solar GmbH Noteworthy 22
GP ALKA-TEX .Plus GP ALKA-TEX .Plus is a surface active additive for the improvement of the alkaline texturing of monocrystalline silicon wafers. The addition of this product to the standard alkaline texture process with KOH/NaOH and IPA (2- propanol) increases the optical yield of the solar cell due to a more
homogeneous surface structure. The cell efficiencies can be increased by around 0.3% absolute.
Product Challenge
One problem of the standard alkaline texture process with KOH/NaOH and IPA is a small process window. With the standard alkaline texturing process it is impossible to adjust one recipe for different wafer qualities. There are always significant differences in the texture quality from wafer to wafer. The challenge is to develop a stable, reproducible and reliable process with better optical characteristics. Another challenge is to decrease the total costs of the texturing process by increasing the throughput and minimizing the consumption of chemicals.
Problem Solved With GP ALKA-TEX .Plus one texture recipe works for different wafer qualities. The number of recipes is reduced to a basic recipe by making only small adjustments. Moreover the appearance of the texture can be improved. The wafer surface becomes more homogenous and the amount of defects can be reduced. On the other hand the bath life time can
The use of GP ALKA-TEX .Plus allows a better controlling of the texturing process. This process makes a stable run to run repeatability possible. The pyramid size which has a great impact of the optical yield and therefore of the cell efficiency is tunable with GP ALKA-TEX .Plus. Moreover, defects and contamination on the surface can be handled and removed during the texturing process.
Product In Detail
The first step in the silicon solar cell production is the texture. The two main processes are the alkaline texturing for monocrystalline wafers and the acid texturing for multicrystalline wafers. This first step removes the saw damage of the wafer and creates a homogenous surface with low reflectivity.
In the standard alkaline texturing process, KOH or NaOH and IPA are used at a process temperature of 80°C in order to etch the surface anisotropically, resulting in a pyramid-shaped surface. The lifetime of one bath is with ~4 to ~30 runs relatively low, for the most wafer qualities a different recipe is needed, and the process is not very reproducible.
The product GP ALKA-TEX .Plus is a chemical additive that improves the alkaline texturing of monocrystalline silicon wafers. Its addition to the bath mainly results in a very homogenous silicon surface with a lower reflectivity compared to the standard alkaline process. These improved optical characteristics increase the total efficiency
In addition, the process in general can be controlled more easily and with a more stable run to run repeatability when using GP ALKA-TEX .Plus. The additive also allows a tunable pyramid size and reduces the amount of chemicals required. Furthermore, the lifetime of the alkaline bath is increased significantly to approximately 30-60 runs. Together with the reduced process time the throughput increases. It is an ESH (environmental, safety and health) compliant as well as a water soluble additive.
The appearance of the additive is liquid with a boiling point of 100°C and a density of ~1.1 g/cm3. The waste disposal procedures are the same as for the alkaline texturing bath.
Innovation GP ALKA-TEX .Plus solves the main problems of the standard alkaline texturing process. These disadvantages are short bath life times, significant differences in the texture performance with different wafer qualities and visible defects on the wafer surface.
Moreover the additive has several positive side-effects which are shorter process times, less chemical consumption and most important for a higher cell efficiency an increased optical yield. There are no disadvantages of the product known, and due to the many advantages the total cost of ownership of the texturing process is better with GP ALKA-TEX .Plus than without it.
When Introduced GP ALKA-TEX .Plus was introduced to the market in March 2009.
Customer Benefits
The customers benefit from a higher efficiency of the solar module. The improved front side of the solar cells leads to a higher optical yield. The cost savings of a lower chemical consumption and a higher throughput of wafers should also be noticeable in the module price.
www.solar-pv-management.com Issue VII 2011
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