My Advice: Understand the Advantages, Disadvantages of Different Solar Cells and Who the Market Leaders Are

This page is designed to introduce you to the various types of solar cells, and to connect you to additional pages where you can learn about the advantages and disadvantages of each type.

Some Basic Terms

Before we start discussing the specifics of different technologies used to produce photovoltaic cells, here are some basic terms to keep in mind:

Solar cell: is a device that converts the energy of sunlight directly into electricity by the photovoltaic effect.

Solar Panel or Solar Module: Solar cells are wired in series and placed into a frame. The size of the frame can vary with manufacturers … as a result of the technology used. A protective coating on the top covers and protects (and sometimes increases the output) of the solar cells. Any number of cells can be connected in series and most commercial modules sold today incorporate 72 cells. .

If you haven't already done so, I suggest you read the background information we've provided in this site about solar energy, irradiance, insolation, peak power ratings for cells, standardized testing conditions for rating solar cells and related topics.

First Generation Solar Cells

Traditional solar cells are made from silicon, are currently the most efficient solar cells available for residential use and account for around 80+ percent of all the solar panels sold around the world. Generally silicon based solar cells are more efficient and longer lasting than non silicon based cells. However, they are more at risk to lose some of their efficiency at higher temperatures (hot sunny days), than thin-film solar cells.

There are currently four types of silicon based cells used in the production of solar panels for residential use. The types are based on the type of silicon used, specifically:

1. Monocrystalline Silicon Cells

The oldest solar cell technology and still the most popular and efficient are solar cells made from thin wafers of silicon. These are called monocrystalline solar cells because the cells are sliced from large single crystals that have been painstakingly grown under carefully controlled conditions. Typically, the cells are a few inches across, and a number of cells are laid out in a grid to create a panel.

Relative to the other types of cells, they have a higher efficiency (up to 24.2%), meaning you will obtain more electricity from a given area of panel. This is useful if you only have a limited area for mounting your panels, or want to keep the installation small for aesthetic reasons. However, growing large crystals of pure silicon is a difficult and very energy-intensive process, so the production costs for this type of panel have historically are the highest of all the solar panel types.

Production methods have improved though, and prices for raw silicon as well as to build panels from monocrystalline solar cells have fallen a great deal over the years, partly driven by competition as other types of panel have been produced.

Another issue to keep in mind about panels made from monocrystalline silicon cells is that they lose their efficiency as the temperature increases about 25˚C, so they need to be installed in such a way as to permit the air to circulate over and under the panels to improve their efficiency.

For more information about monocrystalline solar cells, a more detailed analysis of their advantages and disadvantages and information about leading panel manufacturers click here.

2. Polycrstalline Silicon Cells

It is cheaper to produce silicon wafers in molds from multiple silicon crystals rather than from a single crystal as the conditions for growth do not need to be as tightly controlled. In this form, a number of interlocking silicon crystals grow together. Panels based on these cells are cheaper per unit area than monocrystalline panels - but they are also slightly less efficient (up to 19.3%).

For more information about polycrystalline solar cells, their advantages and disadvantages, and information about leading panel manufacturers click here.

Note: Many of the leading firms make both monocrystalline and polycrystalline solar cells for their panels.

3. Amorphous Silicon Cells

You probably never thought about it before, but most solar cells used in calculators and many small electronic devices are made from amorphous silicon cells.

Instead of growing silicon crystals as is done in making the two previous types of solar cells, silicon is deposited in a very thin layer on to a backing substrate – such as metal, glass or even plastic. Sometimes several layers of silicon, doped in slightly different ways to respond to different wavelengths of light, are laid on top of one another to improve the efficiency. The production methods are complex, but less energy intensive than crystalline panels, and prices have been coming down as panels are mass-produced using this process.

One advantage of using very thin layers of silicon is that the panels can be made flexible. The disadvantage of amorphous panels is that they are much less efficient per unit area (up to 10%) and are generally not suitable for roof installations you would typically need nearly double the panel area for the same power output. Having said that, for a given power rating, they do perform better at low light levels than crystalline panels - which is worth having on a dismal winter's day, and are less likely to lose their efficiency as the temperature climbs.

However, there flexibility makes them an excellent choice for use in making building integrated PV (e.g., roofing shingles), for use on curved surfaces, or even attached to a flexible backing sheet so that they can even be rolled up and used when going camping / backpacking, or put away when they are not needed!

For more information about polycrystalline solar cells, their advantages and disadvantages, and information about leading panel manufacturers click here.

4. Hybrid Silicon Cells

One recent trend in the industry is the emergence of hybrid silicon cells and several companies are now exploring ways of combining different materials to make solar cells with better efficiency, longer life, and at reduced costs.

Recently, Sanyo introduced a hybrid HIT cell whereby a layer of amorphous silicon is deposited on top of single crystal wafers. The result is an efficient solar cell that performs well in terms of indirect light and is much less likely to lose efficiency as the temperature climbs.

Second Generation Solar Cells

Second-generation solar cells are usually called thin-film solar cells because when compared to crystalline silicon based cells they are made from layers of semiconductor materials only a few micrometers thick. The combination of using less material and lower cost manufacturing processes allow the manufacturers of solar panels made from this type of technology to produce and sell panels at a much lower cost.

There are basically three types of solar cells that are considered in this category, amorphous silicon (mentioned above), and two that are made from non-silicon materials namely cadmium telluride (CdTe), and copper indium gallium diselenide (CIGS). Together they accounted for around 16.8% of the panels sold in 2009.

First Solar, the number one producer and seller of solar panels in the world currently makes their solar cells using cadmium telluride. The big appeal of these type of solar cells is that they are inexpensive (currently below $1.00 / watt to produce and heading towards $0.70 / watt). However, as we discuss in the accompanying articles about cadmium telluride (CdTe) and First Solar – there are some concerns about this technology.

Venture capitalists love CIGS solar cells (or at least used to – as they have invested over $2.3 billion into companies developing these cells but have yet to see them be a commercial success) – as they have been able to reach efficiency levels of 20% in the laboratory. Unfortunately it has turned out to be much more difficult to produce CIGS solar cells in mass quantities at competitive prices with anywhere near than efficiency level, so the jury is still out on this technology.

To learn more read our section on CIGS solar cells, how they are made and the advantages and disadvantages of these type of solar cells,

click here.

New Recently a Company based in Idaho has come up with a thin-film monocrystalline solar cell - that uses about 20% of the crystalline silicon in current silicon based cells and has number of advantages. To learn more visit our page on Transform Solar.

Third Generation Solar Cells

Currently there is a lot of solar research going on in what is being referred to in the in the industry as Third-generation solar cells. In fact according to the number of patents filed last year in the United States – solar research ranks second only to research in the area of fuel cells.

This new generation of solar cells are being made from variety of new materials besides silicon, including nanotubes, silicon wires, solar inks using conventional printing press technologies, organic dyes, and conductive plastics. The goal of course is to improve on the solar cells already commercially available – by making solar energy more efficient over a wider band of solar energy (e.g., including infrared), less expensive so it can be used by more and more people, and to develop more and different uses.

Currently, most of the work on third generation solar cells is being done in the laboratory, and being developed by new companies and for the most part is not commercially available.

To learn more about some of the interesting developments in this area, please check our section on Solar Reserach, and the various related articles we are creating about the exciting work being done in this area.

Thank You For Visiting

Hopefully, we've been able to give you a better understanding of the advantages and disadvantages of various types of solar cell technologies in this and the related pages – as selecting the right technology is quite important when considering a roof top installation, especially when you consider how long solar cells are likely to last and keep producing power for you.

Please be sure to look for our upcoming section on Solar Panels, which will have a lot of valuable facts and advice as well.

Please keep in mind that this is a new site and we've only put up about 10% of the information we're planning on and are adding information all the time, so if there's something you were looking for that you didn't find, or if you have a comment, suggestion, or would like to contribute information – please contact us and send us a message and we'll be happy to look into it and get back to you or let you know when it is added.

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