A solar cell is like a sandwich: P-side and N-side, with an empty middle that can push charges. Watch the same cell with no wire and with a wire. Light does the same first job in both. The wire decides if electricity can keep flowing.
Formation. Silicon is doped: boron makes P-type (holes), phosphorus makes N-type (electrons).
A solar cell is a silicon sandwich. We add special extras (doping) so each side has a favorite traveler.
Nothing is flowing yet. These are just two doped crystals sitting side by side — the raw ingredients of a junction.
Carriers do not like being crowded. They wander from high concentration to low concentration — a random walk that becomes a net flux.
Hit reset to put every carrier back on its home side and watch the mixing start again.
An electric field shoves charge. Holes (positive) ride with the field. Electrons (negative) run against it.
Bring P and N into contact. Diffusion starts. Near the interface, electrons fall into holes and vanish as free charge. What remains are uncovered dopant ions: negative acceptors on the P side, positive donors on the N side.
Think of sunlight as a rain of tiny energy balls called photons. If a photon is strong enough, it knocks an electron loose and leaves an empty seat called a hole. That pair is born together. The empty middle of the cell (the depletion zone) has a hidden push. The push sends the electron to the N-side and the hole to the P-side.
A yellow bit of sun energy flies into the sandwich.
If the photon is strong enough: one electron + one hole appear together.
The middle push sends − to N and + to P. They are not allowed to hug again.
No wire: charges pile up. With wire: charges run around and can light a bulb.
Light still makes pairs. Charges still get sorted. They stack on the two ends, like a battery charging. Voltage goes up. Current stays almost zero because there is no road home.
Same light. Same pairs. Same sort. Now electrons can leave through the wire, pass the bulb, and keep moving. The bulb glows. That flowing river is electric current.
Sun is on. Watch the same photons on both sides. Only the right side has a road for current.
Press the steps in order. The lab will set itself so you can watch just that part.
Start at step 1. What does the cell look like before any sunlight?
After light, with NO wire, what grows?
Score: 0 / 0
This is the right-hand picture from the lab above, bigger. Sun on → pairs → sort → current through the bulb. Sun off → the river stops. Same sandwich, same push, same rule: light makes the charges, the wire lets them travel.