ABSTRACT
Readers who are familiar with “photovoltaic (PV) solar cells” please move to the next chapter.This chapter is for those people who heard or read nothing or maybe just something about “photovoltaic cells” (PV cells) which are also called as “solar cells” and they think it is a very complicated subject. This chapter is to dispel the mystery about the subject and to show that it is only as complicated as sharpening a pencil.To mention the word “photovoltaic” could be understandable for scientists or experts, but it is probably meaningless and may frighten away people.The word “photo” is the Greek word for light and everybody knows the word “electricity.” So if one would use “photoelectric cells” the understanding would be easy. We would talk about a device that produces electrical energy when it is exposed to light. But to complicate matters the word “photovoltaic cells” or the expression “solar cells” is used for the devices whose function is exactly that. Why not call them simply “photoelectric” or “solarelectric” cells? The reason is very simple. Scientists
in the nineteenth century were inconsiderate to the people of twenty-first century.Edmond Becquerel, a French physicist in 1839, while studying the effect of light on “electrolytic (battery) cells” discov-ered a relationship between light and electronic properties of materials that certain material converts light directly into electrical energy. The culprit was actually Alfred Smee, who 10 years later coined the term “photovoltaic”17 from “photo” and adding the word “Volta”18 who was an Italian physicist (died more than 10 years before Becquerel discovered this effect), because the battery invented by Volta is credited as the first electrochemical cell. By working with electrolytic cells, which have a positive and a negative electrode, Smee named this device also having a positive and negative electrode, “photo-voltaic cell,” being a derivative of Volta’s “electrochemical cell,” operated not by chemicals, but by light.Heinrich Hertz in 1887 discovered another effect, namely, that when light hits a material, the electrons escape from the material. They first named this as “Hertz effect,” but it was soon renamed as “photoelectric” effect.Figure 2.1 helps us to understand that the similarity in both the inventions of Becquerel’s and Hertz’s is that light produces electrons. Hertz’s invention called “photoelectric” refers to the emission, or ejection, of electrons from the surface of a metal in response to incident light which means the electrons escape from the metal. Becquerel’s invention is in which the electrons in response to incident light escape from the material, but like in a battery cell in an existing electrical field move toward the positive electrode. The chemical battery cell was invented by Volta, so Becquerel’s invention was given the name by Alfred Smee a “photovoltaic” cell.As an interesting note, that nobody understood how the Hertz and the Becquerel effect works, until Einstein in a paper in 1905 described it. This was in importance not comparable to the special relativity theory he published in the same year, 17Palz W (2011) Power for the World, Pan Stanford Publishing, Singapore.18Count Alessandro Giuseppe Antonio Anastasio Gerolamo Umberto Volta (18 February, 1745, 5 March, 1827) was an Italian physicist known especially for the invention of the battery in the 1800s.
