World Library  
Flag as Inappropriate
Email this Article

Photovoltaic effect

Article Id: WHEBN0002003406
Reproduction Date:

Title: Photovoltaic effect  
Author: World Heritage Encyclopedia
Language: English
Subject: Concentrated solar power, Photoelectric effect, Energy development, Arnprior Solar Generating Station, Community solar farm
Publisher: World Heritage Encyclopedia

Photovoltaic effect

The photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light.

The standard and obvious photovoltaic effect is directly related to the photoelectric effect, though they are different processes. When the sunlight or any other light is incident upon a material surface, the electrons present in the valence band absorb energy and, being excited, jump to the conduction band and become free. These highly excited, non-thermal electrons diffuse, and some reach a junction where they are accelerated into a different material by a built-in potential (Galvani potential). This generates an electromotive force, and thus some of the light energy is converted into electric energy. The photovoltaic effect can also occur when two photons are absorbed simultaneously in a process called two-photon photovoltaic effect.

The photovoltaic effect was first observed by French physicist A. E. Becquerel in 1839. He explained his discovery in Les Comptes Rendus de l'Academie des Sciences, "the production of an electric current when two plates of platinum or gold diving in an acid, neutral, or alkaline solution are exposed in an uneven way to solar radiation."[1]

In the photoelectric effect, by contrast, electrons are ejected from a material's surface into vacuum, upon exposure to light. This also generates some electric energy (as the ejected electron is eventually captured on another electrode), though there is typically a high photon energy threshold. The photovoltaic effect differs in that the excited electrons pass directly from one material to another, avoiding the difficult step of passing through the vacuum in between.

Besides the direct excitation of free electrons, a photovoltaic effect can also arise simply due to the heating caused by absorption of the light. The heating leads to an increase in temperature, which is accompanied by temperature gradients. These thermal gradients in turn may generate a voltage through the Seebeck effect. Whether direct excitation or thermal effects dominate the photovoltaic effect will depend on many material parameters.

In most photovoltaic applications the radiation is sunlight, and the devices are called solar cells. In the case of a p-n junction solar cell, illuminating the material creates an electric current as excited electrons and the remaining holes are swept in different directions by the built-in electric field of the depletion region.[2]

See also


  1. ^ Palz, Wolfgang (2010). Power for the World - The Emergence of Electricity from the Sun. Belgium: Pan Stanford Publishing. p. 6. 
  2. ^ The photovoltaic effect. (2006-12-01). Retrieved on 2010-12-12.
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.