Types of Solar Panels: Pros and Cons

There are three main types of solar panels commercially available: monocrystalline solar panels, polycrystalline solar panels, and thin-film solar panels. There are also several other promising technologies currently in development, including bifacial panels, organic solar cells, concentrator photovoltaics, and even nano-scale innovations like quantum dots.

Each of the different types of solar panels has a unique set of advantages and disadvantages that consumers should consider when choosing a solar panel system. 

Monocrystalline Solar Panels

Because of their many advantages, monocrystalline solar panels are the most commonly used solar panels on the market today. Approximately 95% of solar cells being sold today use silicon as the semiconductor material. Silicon is abundant, stable, non-toxic, and works well with established electric generation technologies.

Originally developed in the 1950s, monocrystalline silicon solar cells are manufactured by first creating a highly pure silicon ingot from a pure silicon seed using the Czochralski method. A single crystal is then sliced from the ingot, resulting in a silicon wafer that is approximately 0.3 millimeters (0.011 inches) in thickness.

Monocrystalline solar cells are slower and more expensive to produce than other types of solar cells due to the precise way the silicon ingots must be made. In order to grow a uniform crystal, the temperature of the materials must be kept very high. As a result, a large amount of energy must be used because of the loss of heat from the silicon seed that occurs throughout the manufacturing process. Up to 50% of the material can be wasted during the cutting process, resulting in higher production costs for the manufacturer.

But these types of solar cells maintain their popularity for a number of reasons. First, they have a higher efficiency than any other type of solar cell because they are made of a single crystal, which allows electrons to flow more easily through the cell. Because they are so efficient, they can be smaller than other solar panel systems and still generate the same amount of electricity. They also have the longest life span of any type of solar panel on the market today.

One of the biggest downsides to monocrystalline solar panels is the cost (due to the production process). In addition, they are not as efficient as other types of solar panels in situations where the light does not hit them directly. And if they get covered in dirt, snow, or leaves, or if they are operating in very high temperatures, their efficiency declines even more. While monocrystalline solar panels remain popular, the low cost and rising efficiency of other types of panels are becoming increasingly appealing to consumers.

Polycrystalline Solar Panels

As the name implies, polycrystalline solar panels are made of cells formed from multiple, non-aligned silicon crystals. These first-generation solar cells are produced by melting solar grade silicon and casting it into a mold and allowing it to solidify. The molded silicon is then sliced into wafers to be used in a solar panel.

Polycrystalline solar cells are less expensive to produce than monocrystalline cells because they do not require the time and energy needed to create and cut a single crystal. And while the boundaries created by the grains of the silicon crystals result in barriers for efficient electron flow, they are actually more efficient in low-light conditions than monocrystalline cells and can maintain output when not directly angled at the sun. They end up having about the same overall energy output because of this ability to maintain electricity production in adverse conditions.

The cells of a polycrystalline solar panel are larger than their monocrystalline counterparts, so the panels may take up more space to produce the same amount of electricity. They are also not as durable or long-lasting as other types of panels, although the differences in longevity are small.

Thin-Film Solar Panels

The high cost of producing solar-grade silicon led to the creation of several types of second- and third-generation solar cells known as thin-film semiconductors. Thin-film solar cells need a lower volume of materials, often using a layer of silicon as little as one micron thick, which is about 1/300th of the width of mono- and polycrystalline solar cells. The silicon is also of lower quality than the kind used in monocrystalline wafers.

Many solar cells are made from non-crystalline amorphous silicon. Because amorphous silicon does not have the semiconductive properties of crystalline silicon, it must be combined with hydrogen in order to conduct electricity. Amorphous silicon solar cells are the most common type of thin-film cell, and they are often found in electronics like calculators and watches.

Other commercially viable thin-film semiconductor materials include cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and gallium arsenide (GaAs). A layer of semiconductor material is deposited on an inexpensive substrate like glass, metal, or plastic, making it cheaper and more adaptable than other solar cells. The absorption rates of the semiconductor materials are high, which is one of the reasons they use less material than other cells.

Production of thin-film cells is much simpler and faster than first-generation solar cells, and there are a variety of techniques that can be used to make them, depending on the capabilities of the manufacturer. Thin-film solar cells like CIGS can be deposited on plastic, which significantly reduces its weight and increases its flexibility. CdTe holds the distinction of being the only thin film that has lower costs, higher payback time, lower carbon footprint, and lower water use over its lifetime than all other solar technologies.

However, the downsides of thin-film solar cells in their current form are numerous. The cadmium in CdTe cells is highly toxic if inhaled or ingested, and can leach into the ground or water supply if not properly handled during disposal. This could be avoided if the panels are recycled, but the technology is currently not as widely available as it needs to be. The use of rare metals like those found in CIGS, CdTe, and GaAs can also be an expensive and potentially limiting factor in producing large amounts of thin-film solar cells.           

Other Types

The variety of solar panels is much greater than what is currently on the commercial market. Many newer types of solar technology are in development, and older types are being studied for possible increases in efficiency and decreases in cost. Several of these emerging technologies are in the pilot phase of testing, while others remain proven only in laboratory settings. Here are some of the other types of solar panels that have been developed. 

Bifacial Solar Panels

Traditional solar panels only have solar cells on one side of the panel. Bifacial solar panels have solar cells built on both sides in order to allow them to collect not only incoming sunlight, but also albedo, or reflected light off the ground beneath them. They also move with the sun in order to maximize the amount of time that sunlight can be collected on either side of the panel. A study from the National Renewable Energy Laboratory showed a 9% increase in efficiency over single-sided panels.

Concentrator Photovoltaic Technology

Concentrator photovoltaic technology (CPV) uses optical equipment and techniques such as curved mirrors to concentrate solar energy in a cost-efficient way. Because these panels concentrate sunlight, they do not need as many solar cells to produce an equal amount of electricity. This means that these solar panels can use higher quality solar cells at a lower overall cost.

Organic Photovoltaics

Organic photovoltaic cells use small organic molecules or layers of organic polymers to conduct electricity. These cells are lightweight, flexible, and have a lower overall cost and environmental impact than many other types of solar cells.

Perovskite Cells

The Perovskite crystalline structure of the light-collecting material gives these cells their name. They are low cost, easy to manufacture, and have a high absorbance. They are currently too unstable for large-scale use.

Dye-Sensitized Solar Cells (DSSC)

These five-layered thin-film cells use a special sensitizing dye to help the flow of electrons which creates the current to produce electricity. DSSC have the advantage of working in low light conditions and increasing efficiency as temperatures rise, but some of the chemicals they contain will freeze at low temperatures, which makes the unit inoperable in such situations.

Quantum Dots

This technology has only been tested in laboratories, but it has shown several positive attributes. Quantum dot cells are made from different metals and work on the nano-scale, so their power production-to-weight ratio is very good. Unfortunately, they can also be highly toxic to people and the environment if not handled and disposed of properly.