Silicon is the most widely used material in photovoltaic cell technologies. However, it is not the only one capable of transforming sunlight into electricity. A team of researchers from Princeton University revealed on June 16 in an article in the journal Science that a mineral, perovskite, could be used to design photovoltaic materials. They are less expensive, but they deteriorate faster. Researchers have succeeded in slowing down their rate of degradation to make them an interesting alternative in the manufacture of solar panels.
Perovskites have a shorter lifetime than silicon
There are a wide variety of perovskites that could replace silicon in the design of photovoltaic cells. They are less expensive and simpler to process, but until now their durability was very short when exposed to sunlight. Princeton researchers succeeded in making them more stable through several experiments. The objective is to give them a lifetime similar to silicon while maintaining the efficiency of solar panels.
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For use in photovoltaic cells, perovskites are crystallized. They are combined with chemical compounds or various elements to take this form. Lead is the element most often used to crystallize perovskites. The process of crystallization is done by chemical precipitation, that is, the materials are combined in the form of a liquid solution. A method that can be easily and inexpensively carried out.
The principle of photovoltaic cells is based on the conversion of photons present in sunlight into electrical charge. Perovskites currently convert 17% of photons against 22% for silicon. There is, however, a wide variety of perovskites, including some that may have similar efficiency to silicon.
Raw perovskite often takes on the appearance of a small block with a metallic appearance. Photography: Wikimedia/Leon Hupperichs.
These materials open up the field of possibilities for photovoltaic technologies
In one year of use, perovskites lose a significant part of their performance. This reality comes from the very nature of the crystal, whose atoms are ejected away from it upon exposure to light. The researchers designed a “stopper” which prevents atoms from moving apart and therefore weakening the crystal. The cap is made up of the same atoms as the crystal, which blocks their expulsion. It must still maintain a thickness of 20 nanometers to allow the passage of electrical charges to the layer of the photovoltaic cell that creates the current.
In order to test the lifespan of perovskites, the Princeton scientists observed the deterioration over a short period of time and extrapolated it using a formula. Thus, their calculations determined the moment when the solar panel only works at 80% of its maximum capacity, called T80.
The T80 would be reached after 2100 hours of continuous use of the solar panel, exposed to an extreme temperature of 110°C. In fact, the average exposure temperature is 35°C, which would correspond to a lifespan of five years. If cold and cloudy weather is taken into account, the longevity of the panel can be doubled. This means that regions exposed to inclement weather might prefer the use of perovskites for the sake of cost efficiency.
This technological advance would make the design of solar panels less expensive, but Ars-Technica specifies that their efficiency is lower if we compare the panels individually. The low production cost of perovskite crystals remains a competitive argument. There is also a wide variety of perovskites which have not yet been discovered and whose performance may be more important than silicon. Perovskites can also be used to make energy-efficient LED lamps, reported in early June Trust My Science.
Although silicon is one of the most abundant elements on Earth, it is used in many sectors, including the design of semiconductors. In October 2021, its price had increased by 300% due to a shortage. The discovery of perovskites as alternatives for photovoltaic panels represents a boon in the development of renewable energies.