Although a wide variety of materials are now used in solar cell technology, silicon and its own variety of forms remains the most reliable and affordable solar cell semiconductor material. Even with the steady development of third-generation solar technology, first-generation materials such as silicon are still being developed into home and commercial solar power systems.
The reason is quite simple: silicon is abundant and efficient at its job. These factors ensure that it is not expensive or wasteful for you or me when we switch from grid-connected electricity to solar power. Of course, things have changed since the early years of commercial solar technology, when silicon wafers were twice as thick and only half as long as modern versions. Efficiencies were also much lower, with the energy used in manufacturing a cell often greater than the energy generated by the cell over its lifetime. Today, some thin-film solar cells (second generation technology), which can have a half-life of up to 30 years, can equal their energy cost in one year.
The silicon used in solar cell technology today is not pure crystalline silicon, since in its pure form silicon is a poor semiconductor of electricity. That is why some impurities are added to make it efficient in converting sunlight into electrical energy. If you know the chemistry of solar energy, you know that electrons and their movement are of paramount importance, but crystalline silicon doesn’t allow its electrons to move much. By adding impurities, such as phosphorus, the electrons begin to move and energy is created. Silicon ‘doped’ with phosphorus is called N-type silicon (it has a negative charge), while silicon doped with boron is called P-type silicon. It is to the P-type silicon that the N-type electrons move.
This is all very interesting to the scientists among us, but if you’re just starting to consider solar power as an option, you’ll want to know the best silicon solar panel to choose. Well, first generation silicon cells are wafer-based cells, which means the silicon is cut into thin wafers and layered one on top of the other. Single junction cells comprising N- and P-type silicon layers that create energy between them. These are still the most common form of solar cells, and they are usually rigid and large.
Second-generation thin-film solar cells are less cumbersome and boast higher efficiency, but are built using very different techniques. In essence, the semiconductor material used is in even thinner strips than can be achieved with wafer technology, with vapor deposition being one of the most effective ways to place the material onto a substrate. Silicon is also used here, but in other forms, such as amorphous silicon, which does not retain its crystalline form, or micromorphic silicon, which is a combination of microcrystalline and amorphous silicon. Microcrystalline silicon can absorb a wider range of light and the combination with amorphous makes it extremely flexible. Now, it is possible to use this technology to simply ‘print’ cells, which makes production costs much lower.
Third-generation silicon solar cells look poised to move away from reliance on silicon as a semiconductor, with multi-junction solar cells set to become the mainstream. However, for the moment at least, this generation is out of reach in terms of price for the commercial market. While germanium layers and gallium arsenide layers have become viable, the third indium phosphide layer is still being developed, but still the cost is too high for you or me to worry about.
It can be a bit daunting to read about the technological developments and stories of the silicon solar cell, but there is one very simple fact to remember: that is the area that scientists need to be concerned with. For us, it’s still a matter of efficiency and affordability. Realistically, silicon solar cells will continue to be the number one option on the market for us and with efficiency rates as low as around 15%, a lot of money can be saved by switching to solar power.