Explore Module
Basic Level
Layered structure and charge collection
A typical silicon solar cell has multiple layers optimized for light absorption and charge collection:
- Anti-reflective coating (top): reduces reflection, maximizing photon entry
- N-type silicon (thin layer): electron-rich region where electrons are collected
- P-N junction (interface): where the electric field separates charge carriers
- P-type silicon (thicker base): where holes are collected
- Metal contacts (top and bottom): conduct electrons out to an external circuit
The front contact is designed as a grid pattern to minimize shading while collecting current. The back contact covers the entire rear surface for maximum conductivity.
Why is the N-layer thinner than the P-layer?
Because most photons are absorbed near the surface; a thin N-layer ensures photo-generated carriers are close to the junction's electric field for efficient separation, while the thicker P-layer absorbs longer-wavelength photons deeper in the material.