Updated: May 29, 2019
There are mainly two types of solar panels
1. Mono crystalline
2. Poly crystalline
Mono crystalline cells (mono) are cut from a single crystal ingot are more efficient but more expensive to manufacture. The higher cost lead the way for polycrystalline technology to become the preferred cell type used; however very recently the cost of mono wafers has declined significantly and many manufacturers are shifting back to mono cells due to the higher efficiency.
Polycrystalline cells, also known as multi-crystalline or 'multi' cells, are grown from multifaceted crystalline material (grown in multiple directions) which is cheaper to produce but offers slightly lower efficiency. Both are still widely manufactured and very reliable but mono cells are considered the the superior technology in regards to efficiency. Mono cells offer slightly improved performance with a lower temperature co-efficient and a slightly lower rate light induced degradation (LID) over time.
Why mono technology is more efficient?
The inherent benefits of mono crystalline silicon are due to the uniform crystalline structure free of grain boundaries and lower impurities through the unique czochralski manufacturing process. In comparison poly or mulit crystalline cells have very small but defined crystal boundaries which can act as minute barriers and can be more susceptible to forming micro-cracks after several years due to cyclic stress and thermal expansion.