How is n-type silicon produced?

Silicon is doped with a small amount of an element such as phosphorus, which has five outer electrons. The extra electrons are free to move and carry charge.

How is p-type silicon produced?

Silicon is doped with an element such as boron, which has three outer electrons. The missing electrons leave positive holes that act as charge carriers.

What happens at the p-n junction of a PV cell?

Electrons diffuse from the n-type layer into the p-type layer, forming a depletion region with a built-in electric field. The field pushes freed electrons towards the n-side and holes towards the p-side.

CCEA A-Level Environmental Technology 3930

Fossil Fuels

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Global Action on Energy Conservation and Climate Change

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Energy From the Sun

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The Code for Sustainable Homes

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Energy From the Sun

Photovoltaic cells and semiconductor wafers

3 things to know
AS 1

Overview

The structure of a silicon cell, n-type and p-type silicon, the p-n junction, photon energy, contacts and anti-reflective coating, modules and inverters, the effect of light, temperature and shading, and standard test conditions.

What you need to know

Answer each one before you reveal it.

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Key term

What is a photovoltaic cell?

Key term

Describe the structure of a crystalline silicon PV cell.

Key term

How does the semiconductor wafer in a solar cell generate electricity?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a photovoltaic cell?
Model answer
A photovoltaic cell is a semiconductor device that converts light directly into electricity. Light releases electrons in the cell, producing a direct current.
2
Describe the structure of a crystalline silicon PV cell.
Model answer
A crystalline silicon cell is a thin wafer with a thin n-type layer on top of a thicker p-type base. Metal contacts on the front and back carry the current away.
3
How does the semiconductor wafer in a solar cell generate electricity?
Model answer
The wafer absorbs photons, which free electrons and leave positive holes behind. An electric field at the junction inside the wafer separates them, driving a current.
4
How is n-type silicon produced?
Model answer
Silicon is doped with a small amount of an element such as phosphorus, which has five outer electrons. The extra electrons are free to move and carry charge.
5
How is p-type silicon produced?
Model answer
Silicon is doped with an element such as boron, which has three outer electrons. The missing electrons leave positive holes that act as charge carriers.
6
What happens at the p-n junction of a PV cell?
Model answer
Electrons diffuse from the n-type layer into the p-type layer, forming a depletion region with a built-in electric field. The field pushes freed electrons towards the n-side and holes towards the p-side.

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Fossil Fuels

Global Action on Energy Conservation and Climate Change

Macrogeneration

Microgeneration

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