Solar cell conversion efficiency calculator
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KEY POINTS
Solar cell efficiency is η = Jsc × Voc × FF / incident irradiance, with 100 mW/cm² under standard test conditions. Single-junction efficiency has a ceiling of about 33% for band gaps near 1.1 to 1.4 eV (the Shockley–Queisser limit). Silicon has reached about 27%, and going further means tandem structures with perovskites.
Efficiency from measured values
Standard test conditions (STC) are AM1.5G, 100 mW/cm² (1000 W/m²) and 25 °C. The default cell area of 244 cm² approximates a 156 mm square (M2) cell.
Open-circuit voltage and fill factor from dark saturation current
Jsc is taken from the field above. Each tenfold reduction in J0 raises Voc by about 60 mV (n = 1).
Band gap and theoretical efficiency limit (detailed balance)
Sunlight is approximated as 5778 K blackbody radiation, so results come out a few percent below values calculated with the real AM1.5G spectrum, which includes atmospheric absorption bands (about 33% for Si). Use it to see the trend with band gap.
Main solar cell materials
| Material | Band gap | Theoretical limit (this tool) | Approximate best reported cell efficiency |
|---|---|---|---|
| Crystalline silicon (c-Si) | 1.12 eV | 29.8 % | About 27% |
| Gallium arsenide (GaAs) | 1.42 eV | 29.9 % | About 29% |
| Cadmium telluride (CdTe) | 1.45 eV | 29.7 % | About 23% |
| CIGS | 1.15 eV | 30.0 % | About 24% |
| Perovskite | 1.55 eV | 28.9 % | About 27% |
| Amorphous silicon | 1.7 eV | 27.2 % | About 14% |
Why single-junction efficiency has a ceiling
A solar cell absorbs only photons with energy above its band gap, and any energy beyond the band gap is lost as heat. A small band gap absorbs more light but gives a low voltage; a large one gives a high voltage but absorbs less light. This trade-off caps single-junction efficiency at about 33% for band gaps around 1.1 to 1.4 eV (the Shockley–Queisser limit).
Going beyond the limit requires tandem (multijunction) structures that stack layers with different band gaps. III-V multijunction cells for space and perovskite-on-silicon tandems have reported efficiencies above 30%. Silicon cells have reached about 27%, close to their theoretical limit, with thinner wafers and passivation at the center of further gains.
FAQ
What are standard test conditions?
AM1.5G spectrum, 100 mW/cm² (1000 W/m²) irradiance and a cell temperature of 25 °C.
Why is single-junction efficiency limited?
Photons below the band gap are not absorbed, and energy above it is lost as heat. Balancing the two caps efficiency at about 33%.
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Last updated: October 23, 2026