It's the ratio of actual maximum power to the theoretical Voc×Isc product; closer to 1 means a more efficient cell.

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☀️ Solar Cell — Photovoltaic Effect & IV Curve

Simulate how a p-n junction solar cell converts light to electricity. Explore the IV characteristic curve, fill factor, efficiency, and how temperature and irradiance affect output power.

Energy & Thermodynamics3DEasy60 FPS

About this simulation

This simulator plots a solar cell's full IV characteristic using the Shockley diode equation, then finds its maximum power point by scanning for where V·I peaks along the curve. Change irradiance, temperature and diode ideality factor to see exactly how a cloudy day, a hot roof, or a lower-quality cell drags down open-circuit voltage, short-circuit current, fill factor and overall efficiency — the same numbers on every real solar panel datasheet.

🔬 What it shows

The orange IV curve and cyan power curve plotted together, with the maximum power point (MPP) marked in red and a shaded rectangle showing the fill factor — how close the curve comes to the ideal Voc×Isc rectangle — alongside a diagram of the p-n junction generating electron-hole pairs from incoming photons.

🎮 How to use

Adjust irradiance G, temperature T and ideality factor n, or click a preset (Standard STC, Hot Day, Cloudy, Overcast) to see Voc, Isc, Pmax, fill factor and efficiency η update along with the curve and MPP marker.

💡 Did you know?

Solar panels actually lose efficiency as they get hotter, not gain it — raising temperature lowers the open-circuit voltage by roughly 2 mV per °C for silicon, which is why panel datasheets specify a negative "temperature coefficient" and why panels are mounted with an air gap for cooling.

Frequently asked questions

What is the maximum power point (MPP)?

It's the specific voltage and current combination on the IV curve where the product V×I is largest — real solar inverters use "maximum power point tracking" (MPPT) circuitry specifically to keep the panel operating at this point as conditions change.

What is fill factor?

It's the ratio of the actual maximum power (Pmax) to the theoretical maximum you'd get by multiplying open-circuit voltage by short-circuit current (Voc×Isc). A fill factor close to 1 means a "squarer" IV curve and a more efficient cell; real silicon cells typically achieve 0.7–0.85.

Why does higher irradiance increase output but not proportionally?

Photocurrent (IL) scales almost directly with irradiance G, boosting Isc and Pmax roughly proportionally, but open-circuit voltage only rises logarithmically with IL — so doubling sunlight roughly doubles current but barely nudges voltage, which is why cloudy conditions crater power output more than voltage.

Why does temperature hurt efficiency?

Rising temperature increases the diode's reverse saturation current, which pulls down the open-circuit voltage even as short-circuit current ticks up slightly — since voltage drops faster than current rises, overall power and efficiency fall on hot days, exactly what the "Hot Day" preset demonstrates.

What does the ideality factor n represent?

It's a correction factor in the Shockley diode equation accounting for non-ideal recombination behaviour in a real junction. A value near 1.0 indicates behaviour close to an ideal diode; higher values (up to about 2) reflect more recombination losses and produce a "softer," less efficient IV curve.

⚙ Under the hood

Adjust irradiance and temperature on a Shockley-diode solar cell and watch the IV curve, fill factor and open-circuit voltage shift.

solar cellphotovoltaicIV curvefill factorefficiencyShockley

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install