Difference Between Photoelectric Effect and Photovoltaic Effect

Main Difference – Photoelectric Effect vs Photovoltaic Effect

The two concepts Photoelectric effect and Photovoltaic effect explain how substances react upon the exposure to light. Photoelectric effect describes the emission of electrons from the surface of a substance in response to incident light. Metals often show this property. Photovoltaic effect is the process in which two dissimilar materials in close contact produce an electrical voltage when struck by light. The main difference between Photoelectric Effect and Photovoltaic Effect is that the electrons in Photoelectric Effect are emitted to open space whereas the electrons in Photovoltaic Effect enter a different material.

Key Areas Covered

1. What is Photoelectric Effect
      – Definition, Explanation of the Effect
2. What is Photovoltaic Effect
      – Definition, Explanation of the Effect
3. What is the Difference Between Photoelectric Effect and Photovoltaic Effect
      – Comparison of Key Differences

Key Terms: Electron, Electron Binding Energy, Emission, Incident Light, Photo-current, Photo-electrons, Photoelectric Effect, Photon, Photovoltaic Effect

What is Photoelectric Effect

Photoelectric effect is the emission of electrons from the surface of a substance in response to incident light. Incident light is the ray of light that strikes a surface. This occurs on metal surfaces. The energy of light is absorbed by the electrons in the metal and these electrons are emitted. But, the energy of light should be exactly equal to the energy required for these electrons to be emitted this way.

Figure 1: Photoelectric Effect

The emitted electrons are known as photo-electrons. The energy of emitted light is independent of the energy of incident light. Incident light carries energy in the form of photons. The energy of photons is directly proportional to the frequency of light. If this energy is enough for an electron in the surface to overcome the electron binding energy, it is ejected. If the energy is not higher than the electron binding energy, then the electron is unable to escape. Hence the electron ejection depends on the amount of energy one photon carries.

The absorbed energy is used to release the energy from the surface by overcoming the electron binding energy and the rest is used to increase the electron’s kinetic energy. Then, the electron can be released as a free particle.

What is Photovoltaic Effect

Photovoltaic effect is the process in which two dissimilar materials in close contact produce an electrical voltage when struck by light. This results in the creation of a voltage and an electric current in the material. The produced current is known as photo-current. Here, an ejection of electrons is not going to happen. The electrons absorb energy, but are retained in the substance. This effect can be observed in semiconductors.

Figure 2: Photovoltaic solar panel is an application of photovoltaic effect

When electrons absorb energy, they obtain an excited state. The photons of the incident light should have enough energy to overcome the potential barrier for the excitation of electrons. Then the electrons become free. These free electrons can cross the barrier between two crystals of dissimilar substances. When a negative charge is given to one end of the substance, an electric current will be produced by the movement of electron away from the negatively charged end.

Difference Between Photoelectric Effect and Photovoltaic Effect

Definition

Photoelectric Effect: Photoelectric effect is the emission of electrons from the surface of a substance in response to incident light.

Photovoltaic Effect: Photovoltaic effect is the process in which two dissimilar materials in close contact produce an electrical voltage when struck by light.

Electron Emission

Photoelectric Effect: Electrons are emitted in photoelectric effect.

Photovoltaic Effect: Electrons are not emitted in photovoltaic effect.

Electric Current

Photoelectric Effect: An electric current is not generated in photoelectric effect.

Photovoltaic Effect: An electric current is generated in photovoltaic effect.

Energy Required

Photoelectric Effect:  Photoelectric effect takes place when the energy provided by photons is enough to overcome the electron binding energy.

Photovoltaic Effect: Photovoltaic effect happens when the energy provided by photons is enough to overcome the potential barrier of excitation.

Conclusion

Photoelectric effect is the emission of electrons from a metal surface when exposed to light. Photovoltaic effect is the generation of an electric current in a substance when exposed to light. The main difference between Photoelectric Effect and Photovoltaic Effect is that in Photoelectric Effect the electrons are emitted to open space whereas in Photovoltaic Effect the electrons enter a different material.

Reference:

1. “Photovoltaic effect.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 10 Apr. 2008, Available here.
2. PhysLink.com, Anton Skorucak. What is the Photoelectric Effect?, Available here.
3. “Photoelectric effect.” Wikipedia, Wikimedia Foundation, 17 Nov. 2017, Available here.

Image Courtesy:

1. “Photoelectric effect” (CC BY-SA 3.0) via Commons Wikimedia
2. “2392184” (Public Domain) via Pixabay