The thing on the roof looks dead. It doesn't move, it makes no noise, and there's no smoke.
But every sunny second, something is going on inside. Tiny particles are getting knocked loose and pushed through wires, and that pushing is the power your home runs on.
So how does light actually do that? This page follows one ray of light into a solar cell and out the other side as electricity. If you just want to know which panel to buy, start with Solar Panels instead.
What Is A Solar Cell?
A solar cell is the small square you see when you look closely at a panel. Each one is a thin slice of silicon that converts light directly into electricity, with no moving parts and no fuel.
One cell on its own can only generate a little power. So cells are wired together and sealed behind glass to make a panel, and panels are connected in groups to make an array. That's the whole family tree: cell, panel, array, and it works the same way whether the array powers a cabin or a whole solar farm.
Scientists call this the "photovoltaic" effect, and the cells photovoltaic (PV) cells. It sounds big, but it just means "light makes electricity".
The Trick That Started It All
A young French scientist named Edmond Becquerel noticed something strange in 1839. He was 19, working with metal plates in salty water in his father's lab in Paris. He shone light on one plate, and a meter twitched.
Nobody could explain it for a long time, but that small twitch is the reason your phone can charge from a panel today. (The longer story of how sunlight became home power is on our solar page.)
The big jump came in 1954, when Bell Labs in the US built the first practical silicon solar cell. Its efficiency was about 6%, and within a few years cells like it were powering satellites.
How Does A Solar Cell Generate Electricity?
Here is the whole process, step by step, from light to current.
- Light arrives. Light is made of tiny packets of energy that scientists call photons.
- An electron gets knocked loose. When the cell soaks up a photon with enough energy, an electron breaks free from its atom, like a ball knocked off a shelf. It leaves an empty spot behind, called a "hole".
- The electric field gives it a push. Inside the cell, two thin layers meet. Where they touch, an invisible electric field forms, a bit like a slide that only goes one way. Freed electrons roll down one side and the holes go the other.
- The electrons pile up at one side. Now one side of the cell has extra electrons and the other has too few. That imbalance works like the plus and minus ends of a battery, ready to push energy through a wire.
- A wire lets them flow. Thin metal lines on the cell catch the electrons. Connect a wire from one side to the other, and the electrons flow through it, back to the other side of the cell, to fill the holes. That flow is an electric current.
As long as light keeps arriving, the loop keeps going and the cell keeps generating electricity. That's how solar panels work too: a panel is just lots of these cells sharing the job.
The current only flows one way, so scientists call it direct current, or DC. Remember that, because it matters when the power produced by the cell reaches your house (more on AC and DC in a solar setup).
The Star Material: Silicon
Most solar cells are made of silicon. It comes from quartz, the same kind of rock that shiny beach sand is made of, and silicon minerals make up more than a quarter of the Earth's crust.
Scientists call silicon a "semiconductor". That's just a fancy word for a material that can carry electricity, but only when something gives it a push. Light is the push.
To build the one-way slide, factories mix a tiny pinch of other elements into each layer. One layer ends up with spare electrons (scientists call it n-type) and the other with spare holes (p-type). Where the two layers meet, they create an electric push all by themselves.
Why Not All Sunlight Becomes Electricity
Sunlight is a mix of colours, from blue to red to invisible infrared, and each photon carries a different amount of solar energy.
The cell needs a minimum push to free an electron. A photon with too little energy, like far infrared, passes straight through as if the cell were a window. A photon with more than enough, like blue light, does free an electron, but the extra energy is produced as heat instead.
So silicon is best at turning red and near-infrared light into power. How well a cell handles each colour is called its spectral response, and it's the main reason one silicon cell can never capture all the light. It's also why labs are now stacking a second material called perovskite on top of silicon, to capture more of the blue.
Why Panels Like Cold, Sunny Days
Heat is the other enemy. The hotter a cell gets, the lower its voltage, and the less electricity it can generate.
Every datasheet lists this as the temperature coefficient of power. In independent tests of modern panels, the average was about -0.3% per degree Celsius above 25 °C, the temperature the label numbers are measured at. A panel baking at 60 °C on a summer roof is 35 degrees over that, so it makes roughly a tenth less than its label says.
On a frosty, sunny morning the panel produces a bit more power, and its voltage rises, which matters when you wire several panels in a row. If you live somewhere hot, a temperature coefficient closer to zero is worth paying attention to.
How Solar Panels Work In A Real System
All solar panels use the same trick, but the cells come in a few different types. Monocrystalline panels are the sleek black ones cut from one big crystal, and almost every new panel is one of these now. Polycrystalline panels are the blue speckled ones that factories have nearly stopped making, while thin-film panels are so thin and bendy that some roll up like a yoga mat.
Want to see how the cells sit between the glass, the frame and the junction box? We took one apart in inside a solar panel.
Once the panels generate DC, your house still needs AC, the kind that comes out of wall sockets. An inverter is the translator box that converts one into the other. If your off-grid system stores power in batteries for the night, a charge controller sits between the panels and the batteries so they don't get overcharged on a bright day.
→ How much power would your roof make? Try the solar panel calculator
What Are The Disadvantages Of Photovoltaics?
Solar cells give you clean, renewable energy with no noise, but they're not magic.
They only make power when light hits them, so at night an off-grid system runs on batteries. They make less on cloudy days and when even part of a panel sits in shade. And as you saw above, heat and the colours silicon can't use mean most of the light still ends up as warmth instead of electricity.
Why Solar Cells Keep Getting Better
The crazy part is how far this has come. That Bell Labs cell from 1954 caught about 6% of the light. Today's best solar panels you can buy reach an efficiency close to 25%, and in the lab, cells that stack perovskite on silicon have passed 35%.
Prices fell even faster, so solar is now affordable for ordinary homes. A watt of solar panel cost about $100 in 1976, in today's money. In 2025 it was about 12 cents. That's more than 800 times cheaper, which is why panels now show up on cabins, boats and even road signs.
What sounds futuristic today might be normal in five years. Read more about where solar panels are heading next.
Sources
- U.S. EIA, Photovoltaics and electricity
- PVEducation, Solar cell structure
- PVEducation, Formation of a PN junction
- PVEducation, Absorption of light
- APS News, April 25, 1954: Bell Labs demonstrates the first practical silicon solar cell
- USGS, Silicon statistics and information
- PVEL, 2024 PV Module Reliability Scorecard, PAN performance
- Fraunhofer ISE, Photovoltaics Report
- Our World in Data, Solar (photovoltaic) panel prices
Hard Words
| Term | What it means |
|---|---|
| Photovoltaic effect | The trick where light hits a material and knocks electrons loose, creating a flow of electricity. Noticed in 1839 by Edmond Becquerel. |
| Photon | A tiny packet of light energy. Sunlight is a stream of them. |
| Electron | A tiny particle that can flow through wires. A flow of electrons is what we call electricity. |
| Hole | The empty spot an electron leaves behind when light knocks it loose. |
| Semiconductor | A material that can carry electricity, but only when something gives it a push. For a solar cell, sunlight is the push. |
| Electric field | The invisible one-way slide where the two silicon layers meet. It pushes freed electrons to one side. |
| Direct current (DC) | Electricity that flows one way only. Solar cells and batteries make DC. |
| Spectral response | How well a cell turns each colour of light into electricity. Silicon is best with red and near-infrared light. |
| Temperature coefficient | How much power a panel loses per degree of heat above 25 °C. |
| Perovskite | A crystal material being tested in labs, stacked on silicon to catch more of the blue light. |
Common Questions
How do solar cells work, in one sentence?
Light knocks electrons loose in a thin slice of silicon, an electric field inside the cell pushes them to one side, and a wire lets them flow back as electricity.
Who discovered that light can make electricity?
A 19-year-old Frenchman named Edmond Becquerel, in his father's Paris lab in 1839. A practical silicon solar cell came much later, at Bell Labs in 1954.
Why are solar cells made of silicon?
Silicon is a semiconductor, so it only carries electricity when something gives it a push, and sunlight is the right kind of push. It's also made from quartz, one of the most common materials on Earth.
Why can't a solar cell use all the sunlight?
Some colours of light have too little energy to free an electron and pass straight through. Others have more than enough, and the extra turns into heat.
Do solar panels work worse when it's hot?
Yes. Modern panels lose roughly 0.3% of their power per degree Celsius above 25 °C.
Why do I need an inverter?
Solar cells make DC, but your wall sockets use AC. An inverter converts one into the other.