Home Solar Power: Doping Silicon to Improve Energy Production. (Part 10)

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The following article explains in varying levels of detail how a solar cells use photons produced by the sun to create solar generated electricity. For residential solar energy systems, this is the physical process that makes it all work. This article will also explain how solar cells are doped with specific impurities to enhance the internal electric field that creates the one-way flow of free electrons bumped out of the silicon atoms and into the holes produced in others. It all relates to chemistry, really.

Doping Silicon Cells to Create Home Solar Arrays

Introducing impurities, called dopants, into the silicon making up the solar cell creates the one-way flow of electrons necessary to produce electricity more efficient. Two differently doped silicon wafers are layered together to create this flow. The next section details out the dopants that are often mixed with solar grade silicon to improve efficiencies.

Boron (p-type): Boron is an element containing three electrons within it's atomic structure, unlike silicon, which has four outer electrons. So wherever boron is introduced into the lattice, a hole is created due to the absence of an electron. This hole creates a net positive charge and is filled by a neighboring electron vibrating in to fill the hole there, and leaving a new hole. These positively charged holes move about. Boron doped silicon is also called p-type, because the freely moving charge is positive.

Phosphorus (n-type): Phosphorus atoms have 5 outer electrons, one more than silicon. Wherever a phosphorus atom is introduced into the lattice, it has a complete set of 4 electrons to share with its 4 silicon neighbors and a 5th electron with no bond to fill. The fifth external electron rotating around the core of the atom bumps free of the atom and moves throughout the silicon wafers or lattice structure. So the introduction of phosphorus provides an electron that moves within the crystal lattice. This type of doped silicon is called n-type because the freely moving charge is negative.

Solar Cells, Electricity and the P-N Junction: What?

The magical flow direction needed to provide current of positive charge in one direction and negative charge in the opposite is created where these two differently doped silicon wafers are "mashed together" as a diode. The surface where the where n-type silicon meets p-type silicon is called the p/n junction.

An interesting aspect to define, the two materials each containing an opposite charge when placed side-by-side create an electric field where electrons pass back and forth. This simple structure is called a diode; an important and necessary processing step as silicon atoms are manufactured into silicon grade solar cells often used in the creation of residential solar panel arrays.

At the p-n junction, the extra phosphorus electron breaks free and wanders until it falls into a hole near a boron atom. Because the phosphorus atom starts out neutral, neither having a negative nor a positive charge due to the loss or addition of an electron, it will have a net positive charge when it looses it's negative electron. Similarly, the boron site, which was electrically neutral, now has one more electron, which makes the net charge at the site negative.

This process continues all along the region between n-type and p-type silicon, with extra phosphorus electrons crossing over to fill boron holes. Creating two areas with opposite atomic charges, this process creates two charges within the silicon PV cell. The result is a flow of electrons from one side to the other and the production of an electric current. The electric field is produced within the silicon wafers at the p-n junction of the diode.

Understanding How Solar Energy Fits into the Mix

We are at the dawn of a solar revolution in the United States. Every aspect of the solar industry is experiencing explosive growth. Currently, there is huge demand and great expansion across the solar PV cell manufacturing industry. Specifically, the production of solar grade silicon. There is added demand for solar sales personal as well as huge demand for solar installation crews with appropriate certification. Opportunities abound everywhere.

The renting of a solar energy system for your home is a new, attractive twist to the idea of switching to renewable energy. With the adoption of a leasing or rental model for residential solar electric systems, an average homeowner can now go green at home as well as build a part-time, solar energy business.

Information about the Author: At Solargies, our goal is to spread the use of renewable solar energy as simply and as rapidly as possible. Daniel Stouffer is a freelance writer and solar energy consultant. Find out how to rent a solar energy system at: => www.reThinkingSolar.com Education and Reference Articles: http://www.article-buzz.com

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