Renewable Energy

Monocrystalline solar panel.

Lifetime production for solar depends on the type of cell

Solar photovoltaic (PV) technologies were largely developed as a result of the need to provide power in space, and factors in space influenced the chemistry development of these technologies. P-type cells were produced because of their better resistance to cosmic radiation and they are still the leading type of solar cell available on the market today. But they are not as effective at resisting degradation from sunlight on Earth. Although most investment into solar stemmed from space travel, another configuration, the N-type cell, features better performance, but it comes at a price.

Solar PV panels utilize a semiconductor material to generate electricity when exposed to sunlight. Most solar panels, from rooftops to solar farms, utilize crystalline silicon as that semiconductor material. However, to generate electricity, these silicon wafers are modified to either attract or release electrons. Silicon has three electron shells, and its outer shell hosts four electrons. For P-type solar cells, an element with only three electrons in its outer shell, usually, boron, is added to the silicon to get electrons moving. For N-type solar cells, an element with five electrons in its outer shell, usually phosphorous, is added to the silicon for this reason.

Why does this matter? When anticipating the return on investment for a solar PV system, understanding the type of solar cells being used will help in determining the estimated level of solar production over time, and therefore, the system’s overall value. P-type solar cells are subject to a process called light-induced degradation (LID). This happens when a solar panel produces less electricity than its rated capacity as a result of boron reacting with oxygen upon illumination of the solar cell. N-type solar cells, on the other hand, do not experience this initial degradation because they do not contain the boron. Another factor that influences lifetime production of the solar PV system is temperature degradation. P-type solar cells are more susceptible to power loss the hotter it gets, whereas N-type cells perform significantly better under these conditions. In general, P-type solar panels are estimated to degrade approximately 0.5% annually, while N-type cells can maintain more electrical integrity over the life of the system.

But N-type solar cells come with added cost. These solar cells are more expensive to produce and are an added upfront cost when purchasing solar power, although long-term calculations can show N-type cells to be more cost effective over time and easier to maintain. This is particularly relevant depending upon the location of the solar installation. In hot climates, P-type solar cells have a history of performing even worse than annual degradation estimations, and in some instances, have required the reinstallation of new solar panels well before the typical lifespan. Therefore, understanding the chemistry of a solar PV system can help in evaluating the difference between a system’s cost and worth.