Turn I–V measurements into clear performance insights fast. See Voc, Isc, Pmax, and efficiency together. Use it for design checks, classes, and reports daily.
Fill factor describes how “square” the I–V curve is near the maximum power point.
Pmax = Vmp × ImpFF = Pmax / (Voc × Isc)η = Pmax / (G × A)v = qVoc/(n k T):FF₀ ≈ (v − ln(v + 0.72)) / (v + 1)| Voc (V) | Isc (A) | Vmp (V) | Imp (A) | Pmax (W) | FF |
|---|---|---|---|---|---|
| 0.62 | 0.038 | 0.50 | 0.035 | 0.0175 | 0.74 |
| 0.58 | 0.032 | 0.46 | 0.028 | 0.0129 | 0.69 |
| 0.70 | 0.041 | 0.58 | 0.038 | 0.0220 | 0.77 |
These examples are illustrative. Always use your measured test conditions.
Fill factor (FF) summarizes how “square” a solar cell I–V curve is near its power-producing region. It is defined by the ratio between maximum electrical power and the ideal product Voc × Isc. Two devices can share the same Voc and Isc, yet show different FF because losses reshape the curve.
This tool uses the standard test points: open-circuit voltage Voc (current is zero), short-circuit current Isc (voltage is zero), and the maximum power point Vmp and Imp. It computes Pmax as Vmp × Imp (or accepts Pmax directly), then evaluates FF = Pmax/(Voc × Isc).
Measured FF depends on technology and quality. Many crystalline-silicon cells often report FF in the ~0.70–0.85 range under standard irradiance, while thin-film devices may be lower depending on series resistance and recombination. A consistent FF drop across samples is often an early sign of contact or metallization issues.
Power output scales as Pmax = Voc × Isc × FF. If you also provide cell area and irradiance, the calculator estimates efficiency using η = Pmax/(G × A). Under a common reference of G = 1000 W/m², a higher FF directly increases Pmax and therefore raises η, even when Voc and Isc stay constant.
Series resistance (contacts, bulk resistance, interconnects) bends the I–V curve downward near Vmp by creating voltage loss under load. Practically, Rs lowers Vmp and can also reduce Imp at high current. The FF penalty can be substantial because the “top-right corner” of the curve collapses first, shrinking the usable rectangle.
Low shunt resistance (leakage paths) increases current loss near Voc and rounds the curve, lowering FF even if Isc looks normal. Recombination and poor junction quality can also soften the knee of the curve. When you see FF loss alongside reduced Voc, the issue may be junction-related rather than purely resistive.
The optional ideal estimate uses normalized voltage v = qVoc/(n k T). Higher temperature increases T, usually reducing v for the same Voc and lowering the estimated ideal FF. The ideality factor n (often between 1 and 2) captures diode behavior; higher n reduces v and typically predicts a lower ideal FF, helping benchmark measured losses.
Use consistent illumination, stable temperature, and verified units. Record Voc and Isc under the same conditions as Vmp/Imp. Check that V and A prefixes (mV, mA, mW) are correctly selected. If results show FF above 1, it usually indicates a unit mismatch or a Pmax value taken from a different irradiance level.
Fill factor is the ratio of maximum power to the product of open-circuit voltage and short-circuit current: FF = Pmax/(Voc × Isc). It indicates how square the I–V curve is near the knee.
You need Voc and Isc plus either Vmp and Imp (so Pmax = Vmp × Imp) or a direct Pmax value. Units must be consistent for voltage, current, and power.
It depends on technology and conditions. Many good crystalline-silicon cells often fall around 0.70–0.85 at standard irradiance. Lower values can indicate resistive loss, leakage, or measurement issues.
Series resistance causes voltage drop under load, flattening the curve near the maximum power region. This reduces Vmp and sometimes Imp, shrinking Pmax while Voc and Isc may change less.
Yes. Provide cell area and irradiance to estimate η = Pmax/(G × A). The tool converts common area and irradiance units, then reports efficiency as a fraction in the results list.
It is a benchmark predicted from normalized voltage v = qVoc/(n k T) using an approximation. Comparing FF to FF₀ helps quantify losses from resistive effects, leakage, and non-ideal diode behavior.
FF above 1 is not physically valid and almost always indicates unit or input mismatch. Common causes include mixing mA with A, mV with V, or entering Pmax from a different test condition.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.