# How a Solar Panel Works

How a solar panel turns sunlight into electric current, from light knocking electrons loose in silicon cells to the flow that lights a bulb\.

By vivid\-dolphin\-9ba7a786

Topic: Energy

[Open the interactive Jig](https://ask.jig.com/j/gAbD2R0PPG8K)

## Transcript

### 1. Sunlight in, electricity out

A solar panel has no moving parts, yet it makes electricity whenever light falls on it\. The bulb here is powered only by the sunshine landing on the panel\. Let's find out how\.

On a clear day, sunlight brings about 1,000 watts of power to every square metre of ground\.

### 2. A grid of silicon cells

Under a sheet of tough glass sit 60 cells, 10 across and 6 down\. Each cell is a thin slice of silicon, an element found in ordinary sand\. The fine silver lines printed on top are wires that collect the electricity\.

A cell is only about 0\.2 millimetres thick, roughly three human hairs side by side\.

### 3. A sandwich of layers

Let's magnify one cell and slice it open\. A blue coating helps it soak up light instead of reflecting it\. Below are two kinds of silicon: a thin top layer, called n\-type, with spare electrons, and a thick lower layer, called p\-type, with holes where electrons are missing\.

Not to scale: the real top layer is far thinner than shown here\.

### 4. Light knocks electrons loose

Light travels as tiny packets of energy called photons\. When a photon is absorbed by the silicon, it can knock an electron free, leaving a hole behind\. Press the button to send in a photon\.

### 5. The junction sorts the charges

Where the two layers meet, called the junction, there is a built\-in electric push\. It sends freed electrons up into the top layer and holes down into the bottom layer\. Charges pile up on each side, like water behind a dam, ready to flow\.

Each silicon cell makes only about half a volt, whatever its size\.

### 6. Close the circuit

Join the top and bottom of the panel with a wire and the electrons have somewhere to go\. They flow out through the silver lines, round through the bulb, and back into the bottom of the cell, where they fill the holes\. That steady flow is an electric current\.

Electrons are never used up\. They go round and round, carrying energy to the bulb\.

### 7. More light, more current

Slide the clouds over the sun and watch\. Fewer photons free fewer electrons, so less current flows and the bulb dims\. Panels still work on cloudy days, just with less output\.

Today's panels turn about one fifth of the sunlight that hits them into electricity\. The rest is reflected or warms the panel\.

### 8. Cells add up

One cell gives about half a volt, so all 60 are linked in a chain, one after another\. Together they push about 30 to 40 volts out of the junction box on the back\. At home, a box called an inverter changes this into the kind of electricity our sockets use\.

A panel makes direct current \(DC\)\. Homes use alternating current \(AC\)\.