Solar cell encapsulation tests

I tested several encapsulation materials on properties such as weather resistance, weight and transmission loss. Measurements are done with the solar cell curve tracer. Note that the reflection is also measured because the tested solar cells are placed at an angle of 30 degree; this is the average sun angle in the summer in the Netherlands:

Bare solar cells exposed to the elements

I wondered what would happen when a solar cell is exposed outside in the rain without any protection.

After some weeks already I saw a huge degradation of the performance. The result is not surprising, protection can’t be neglected. I will divide solar cell corrosion in three types:

• Metallization corrosion, increases in RS. This is clearly visible.
• Light sensitive surface corrosion.
• Antireflection coating deterioration.

Here are some graphs of a corroded solar cell:

EVA film test

EVA film (Ethylene-vinyl acetate) is one of the most used encapsulation materials. However it is heavy, 500g/m2. Also, EVA has relatively high moisture diffusivity. The transmission loss of EVA, measured with the solar cell curve tracer and the slide projector, is 6%. Note that this is not a measurement under laboratory conditions and only used for comparison.

Anti-Reflection Coatings

Much profit can be taken from anti-reflection coating, see pveducation.

Solar cell encapsulation development

For the solar bike I have developed my own solar cell encapsulation that is weather resistant, lightweight and efficient; the total loss is less than 2% inclusive reflection loss.