When evaluating photovoltaic modules, it’s essential to understand the technical features that differentiate them.
Datasheets provide plenty of information, but what are the real key differences? And which technologies deliver the highest performance?
Cell Doping: N-type vs P-type
Solar cells are made of silicon atoms, each containing four valence electrons that form stable bonds with neighboring atoms. To enable electrical conduction, instability must be introduced by adding atoms with one more or one fewer valence electron:
P-Type Cells
Some silicon atoms are replaced with atoms that have one fewer valence electron. Since electrons carry a negative charge, these cells are referred to as positively doped.
N-Type Cells
Some silicon atoms are replaced with atoms that have one extra valence electron. Since electrons are negatively charged, these cells are considered negatively doped.
N-type cells show significantly stronger potential for efficiency improvements compared to P-type cells. For this reason, many manufacturers are shifting toward N-type designs.
Cell Technologies
Another key differentiator is the cell manufacturing technology. The three main families are:
- Heterojunction (HJT)
- All Back Contact (ABC)
- TOPCon, an evolution of traditional PERC cells
Each cell type has unique characteristics, but in general:
- HJT and ABC technologies exhibit lower degradation over time and higher conversion efficiencies
- ABC cells also deliver superior performance under partial shading
Cell Assembly Methods
The most common assembly methods are:
- Half-cell: the cell is cut in half
- Shingled: the cell is cut into five strips and overlapped like roof shingles
There is no clear data showing a significant performance gap between the two. Today, these should be viewed simply as two alternative assembly approaches.
Dual-Glass vs Bifacial Technology
The terms dual glass and bifacial are often confused, but they are not the same.
Bifacial
The module can generate energy from both sides.
This can be achieved through:
- Dual-glass with transparent rear glass
- Front glass with transparent backsheet (e.g., transparent Tedlar)
A bifacial module is not necessarily dual-glass, and vice versa.
Dual Glass
- Cells are encapsulated between two sheets of glass (usually 1.6–2.0 mm).
- Benefits: higher resistance to microcracks, lower degradation.
- Trade-off: slightly lower impact resistance in drop-ball tests (-8/10%).
Hail Resistance
All photovoltaic modules certified under IEC 61215 are tested to withstand hailstones of 25 mm at 83 km/h.
Some models carry additional certifications for larger hail sizes (30/40 mm).
