Perovskite Solar Cells

The efficiency of a solar panel is a measure of the amount of incident sunlight that is converted into electricity. In other words, a solar panel module rated 25% efficient only converts 25% of the total sunlight that falls on its surface into usable electricity.


A major determinant of efficiency is the type of material and technology used in making the solar cells. Advances in solar technology has seen a continuous rise in efficiency ratings of mass-marketed solar panels from just 12% to almost 24%. Yet at the present, much of the solar industry research and development effort revolves around developing more efficient solar cells. These efforts are driven by the need to harvest more electricity from the solar cells per installation space. Supported by new technologies, sustained research and development efforts, effective business models, innovative policies and access to capital, the solar industry is a dynamic one that continues to push back on existing limitations.


The most important breakthrough in solar cell technology in recent years is the optimization of perovskite solar cells. The technology has developed rapidly from 3% in efficiency in 2006 to 25% today making it the most exciting and talked-about thing in the solar community.


What Are Perovskites?

Learn everything you need to know about how solar panels are made here. In summary, traditionally, solar cells are made from purified silicon extracted from quartz sand. The silicon is cut into wafers and doped with elements that turns the silicon into a semiconductor of electricity. Instead of silicon, this new technology depends on perovskites, a lightweight calcium titanium oxide material that was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named after Russian mineralogist L. A. Perovski.


Perovskite are one of the most abundant materials on earth though 72% of perovskites deposits are buried deep in the earth's mantle core. Perovskite has been mined in Arkansas (United States), the Urals (Russia), Switzerland, Sweden, and Germany. All the types of perovskites found in nature share similar dense crystalline structure like crystalline silicon. In 2009, it was known that they were able to interact with sunlight in a similar way as silicon.


Perovskites can also be synthesized artificially. In fact, 'perovskite' can be used to refer to a class of materials with crystal structure similar to that of the calcium titanium oxide that occurs in nature. There is a wide flexibility of elements that can be made into perovskites: 90% of the elements on the periodic table. Not only the metallic elements of nature but also inorganic materials can be made into perovskites by a process that is cheaper than mining perovskite found in nature. It was the discovery that a perovskite could be easily made from both organic and inorganic materials by Henry Snaith at the University of Oxford and the demonstration of the discovery in photovoltaic application in 2008 by Tsutomu ‘Tom’ Miyasaka from Toin University of Yokohama, Japan to Henry Snaith, that set the solar industry and solar energy researchers buzzing.


Miyasaka’s cell delivered an efficiency of just 3.8% But in just 9 years, efficiency of perovskite cells had leaped to 22%. It took traditional solar panels 40 years to cover the same distance.

How Perovskite Cells Can Change the Game

  1. Perovskite solar cells can be made in a wide range of colours. They can also be made to be either opaque or transparent. This makes possible a wide range of opportunities in architectural and exterior designs.

  2. They are very lightweight and large quantities can be easily and cheaply transported. It also makes them easy for deployment in remote areas and off-grid settings.

  3. Perovskites can be dissolved in solvents and 'printed' over a typical silicon cell with the help of liquid inks to complement its efficiency.

  4. Their greatest promise is that the manufacturing process is very cheap!

Barriers

Because of its great promise, researchers have been working to break down barriers that limited its commercialization. One of such limitations is the short lifetime of the cells. Typical perovskite devices degrade within minutes or hours to non-functional states. This is because they are easily susceptible to atmospheric moisture, oxygen, extended periods of light, or high heat. The solar community has been largely focused on increasing the operational lifetime of perovskite cells, to competitive levels with traditional solar panels that can last up to 30 years.


Oxford PV, Not Yet Really Perovskite

In 2020 Oxford PV, a company with links to Oxford University developed silicon wafers that can be coated with perovskite solution to give a world-record breaking 29.52%. By 2021, Oxford PV had raised funds and was settling plans to start manufacturing perovskite solar panels. They are yet to start offering their panels to buyers.


Though this 'dual layer solar cell' in which a layer of perovskite is laid over a silicon wafer, meets the singular most important challenge of any new innovation in solar cell technology, namely, higher efficiency, it is still an elementary solution. The solar panels Oxford PV will offer would be the traditional solar panels complemented with an extra layer of perovskite wafer. The solar community continues to invest research and development efforts into the development of an independent perovskite solar panel that would truly change the game.

A Petrovskite Solar Cell. Source: University of Baths Blog.

FUNFACT: Scientists have shown that perovskite can be used in data transfer technologies that can allow allowing transfer speeds 1,000 times faster than traditional electronic data transfer technology! [Read the Forbes article here.] Perovskites may well be the mineral discovery that will decide the future, not only of solar, but of computing and digital communications.


ALSO: Perovskites are being investigated for use as battery electrodes with a high lithium-ion storage capacity, as a type of photobattery. This means that they also have not only electricity generation capabilities but also charge storage capabilities.


ALSO: Perovskites emit light in a way that can be controlled meaning that they can spawn the next generation of LED lights with high colour quality.

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