Verifying my understanding of solar cells and semiconductors

In summary, solar cells are made of semiconductors with a band gap of 1 eV. Light is absorbed by the semiconductor, creating an electron-hole pair. The electron and hole must be separated in order to contribute to the current. This is achieved through a p-n junction where an element like phosphorous can add an electron (n-type) and an element like boron can remove an electron or add a hole (p-type). When n-type and p-type semiconductors are brought together, they create an electric field that can separate the electron and hole, allowing current to flow in the solar cell.
  • #1
themadquark
22
1
My base understanding of the solar cell is as follows: Light hits metal in solar cell and emits electron via photoelectric effect. There is n-type silicon which has an overall negative charge due to excess electrons. There is also p-type silicon which has an overall positive charge due to a deficiency of electrons. A voltage is produced by this, but in order to keep current flowing the electrons being emitted via the photoelectric effect supply the n-type silicon with electrons to keep current flowing.

My understanding is that an element such as Phosphorous can be added to silicon to produce excess electrons due to it's five valence electrons and silicon's four. Whereas an n-type semiconductor and that an element such as Boron can be used to produce a deficiency in electrons as Boron only has three valence electrons.

Could somebody please check my understanding and correct me where I am incorrect?
 
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  • #2
Solar cells are not made out of metals but rather out of semiconductors, with a band gap around 1 eV to match the solar spectrum. Light from the sun hits the semiconductor and is absorbed, producing an electron-hole pair known as an exciton. Ultimately, the electron must be taken out one end of the cell to contribute to the current - it recombines with the hole after completing the circuit.

A common way to separate the electron and the hole is with a p-n junction, similar to what you describe. Exactly as you say, phosphorous can "dope" silicon and add an electron (producing n-type) and boron can dope silicon and remove an electron, or add a "hole" (producing p-type). Importantly, n-type and p-type semiconductors are still neutral! Neutral P + neutral Si must be neutral overall. However, when you bring n-type and p-type semiconductors together, the electrons from the n-type material flow into the p-type material to combine with holes (or to replace the electron deficiency). *This* leaves the n-type material positively charged (it lost electrons) and the p-type material negatively charged (it gained electrons). The two layers of charges produce an electric field (known as the built-in electric field), and that electric field can separate the electron and hole produced by an absorbed photon, thereby driving the current in the solar cell.
 

Related to Verifying my understanding of solar cells and semiconductors

1. How do solar cells work?

Solar cells are made of semiconductor materials, usually silicon, that have been specially treated to have a positive and negative charge. When sunlight hits the cell, it causes the electrons in the material to become excited and move from the negative side to the positive side, creating an electric current.

2. What is the role of semiconductors in solar cells?

Semiconductors play a crucial role in solar cells because they are responsible for converting the sun's energy into electricity. The semiconductor material used in solar cells has properties that allow it to absorb sunlight and generate an electric current.

3. How efficient are solar cells?

The efficiency of solar cells depends on various factors, such as the type of material used and the design of the cell. However, the most efficient solar cells currently on the market have an efficiency of around 22%, meaning they can convert 22% of the sunlight that hits them into electricity.

4. Can solar cells work without direct sunlight?

Solar cells do not require direct sunlight to work. They can still generate electricity on cloudy days or in shaded areas, although their efficiency will be lower compared to when they are exposed to direct sunlight.

5. How long do solar cells last?

The lifespan of solar cells can vary depending on the quality of the materials and how well they are maintained. On average, solar cells can last for 25-30 years, but some can last even longer with proper care and maintenance.

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