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Photovoltaic cells, also known as solar cells, are the working parts of solar panels. They convert solar energy into electricity through a process known as the "photoelectric effect."

This process happens because the electrons in the silicon atoms that make up the photovoltaic cell exist in various energy states, and at the highest energy state, which is achieved after absorbing energy from sunlight, they become free of the atom and are conducted away from the solar cell as electric current.

Photovoltaic cells are the type of solar power generation that is used in rooftop solar systems and other small-scale solar power.

Types Of Photovoltaic Cells

There are four types of photovoltaic cells that are commonly manufactured and used: single-crystal, polycrystalline, ribbon, and amorphous silicon cells.

Most photovoltaic cells are single-crystal silicon cells. They are made by purifying, melting, and crystallizing silicon into ingots. These ingots are then sliced wafer-thin, each wafer becoming an individual cell.

Single-crystal silicon solar cells have a uniform color. They are normally blue or black. A metal grid conducts the electrons released by the cell in operation and a lead conducts the collected electrons away as an electric current.

Polycrystalline photovoltaic cells are made of a lower grade of silicon than single-crystal cells and are cheaper, but less efficient at producing electricity.

Ribbon silicon cells are produced by forming the molten silicon into a ribbon rather than an ingot. All three of these types of photovoltaic cell work essentially the same.

The last type of photovoltaic cell, amorphous silicon cells, is different from the other three in that it has no uniform crystalline structure. Amorphous silicon photovoltaic cells are also known as thin film silicon cells.

Amorphous silicon cells are manufactured by allowing very thin films of silicon to form from silicon vapor onto a base of plastic, glass, or metal in a vacuum.

The energy potential of amorphous silicon cells is less than half that of crystalline silicon cells. Also, the cells undergo a steep drop in efficiency within a few weeks after being first put to use, usually about a 15% decline after six weeks. However, they are potentially much cheaper to manufacture than crystalline cells, so research is in progress to improve the efficiency.

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Photovoltaic Cells

Price Of Photovoltaic Cells

Photovoltaic cells are priced per unit of peak power generation, i.e., per watt, kilowatt, etc. One goal of solar-power research is to lower the price or cost per unit of electricity to the point where it is competitive with other forms of power generation, especially fossil fuel power such as from coal or natural gas.

In fact, solar power is already very close to being competitive in price with natural gas, and can be considered competitive with coal power generation once the environmental cost of the latter is factored in.

Photovoltaic Cell Efficiency

The efficiency or conversion efficiency of a photovoltaic cell is the percentage of solar energy hitting the cell which is converted into electricity. The higher the conversion efficiency, the greater the cell's output for a given intensity of sunlight.

By increasing the conversion efficiency of solar cells, the cost per kilowatt of solar power can be reduced, given comparable manufacturing costs for the higher-efficiency cells. In fact, both conversion efficiency and manufacturing cost have been improved dramatically over the past few decades.

The earliest solar cells had a conversion efficiency of just one or two percent. Today's monocrystalline photovoltaic cells are approaching just under 40% in efficiency.

Multiple-layer solar cells have a theoretical efficiency limit of 86%. As the efficiency of solar power production improves, so does its attractiveness as a power source for both home solar power and commercial applications.