The Photovoltaic Effect
The photovoltaic (PV) effect is the physical process through which a solar cell converts sunlight into electricity. When photons from sunlight strike a semiconductor material (typically silicon), they transfer their energy to electrons, allowing them to flow as electric current.
Solar Cell Structure
A typical crystalline silicon solar cell consists of a p-n junction formed by doping silicon with phosphorus (n-type) and boron (p-type). When light hits the cell, electron-hole pairs are created near the junction, and the built-in electric field separates them, generating a voltage.
Key Performance Metrics
- Efficiency: Modern monocrystalline cells achieve 20-24%, while PERC and TOPCon cells reach 24-27%.
- Fill Factor: The ratio of actual maximum power to theoretical power — typically 75-85% for quality cells.
- Temperature Coefficient: Power output decreases ~0.35%/°C above 25°C — critical for hot climates.
System Architecture
A complete PV system includes: solar modules → DC combiner box → charge controller/MPPT → battery bank (optional) → inverter → AC distribution panel → loads. Understanding this flow is essential for system design.