Solar cell
A semiconductor device, usually a doped silicon wafer with metal contacts, that converts sunlight directly into direct-current electricity via the photovoltaic effect.
A solar cell is the basic unit of a PV module. Commercial cells are cut from silicon wafers, today mostly the M10 (182 mm) and G12 (210 mm) formats, and are typically laser-split into half or third cells to reduce resistive losses. A single silicon cell produces an open-circuit voltage of roughly 0.65–0.75 V, so 54 to 72 full-cell equivalents are wired in series inside a module.
Here G is irradiance (1,000 W/m² at STC), A the cell area and FF the fill factor, typically 0.80–0.85 for good silicon cells. Mass-produced cell efficiencies in 2024–2025 were roughly 23% for PERC, 24.5–26% for TOPCon and heterojunction, according to the ITRPV roadmap. Laboratory records for silicon exceed 27% (back-contact cells, LONGi 2024–2025), close to the theoretical silicon limit of about 29.4%.
Module efficiency is 1–3 percentage points lower than cell efficiency because of gaps between cells, frame area and optical losses at the glass and encapsulant.
Related terms
All terms →- Photovoltaic effect
The generation of a voltage and electric current in a semiconductor junction when it absorbs photons with energy above the material bandgap.
- Monocrystalline silicon
Silicon grown as a single continuous crystal, usually by the Czochralski method, giving the highest-efficiency and now dominant wafer type for PV.
- PERC (Passivated Emitter and Rear Cell)
A silicon cell design that adds a passivating dielectric layer to the rear surface, reducing recombination and reflecting light back into the cell.
- TOPCon
Tunnel Oxide Passivated Contact: an n-type silicon cell whose rear uses an ultra-thin oxide and doped polysilicon layer to extract current with minimal recombination.
- Heterojunction (HJT) solar cell
A cell that sandwiches an n-type crystalline silicon wafer between ultra-thin amorphous silicon layers, giving very high voltage and a low temperature coefficient.
- Kilowatt-peak (kWp)
The DC power rating of a PV module or array under Standard Test Conditions; the conventional unit of installed solar capacity.