This article details the process of how solar electric cells are mixed with specific impurities to enhance their electric efficiencies. The silicon that is doped enhances the transfer of free electrons between the silicon wafers. It all relates to chemistry and physics in many ways.

In some detail, we will also describe how a solar PV cells use photons created and distributed by the sun to create solar generated electricity. For home solar power, this is the physical process, called the photoelectric effect, makes it possible to create passive solar energy simply from sunlight.

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 contain five electrons rotating around their nucleus. This is 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.

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