The Future of Solar Energy | Perovskite Solar Cells

the earth receives enough energy in a single hour of sunlight to power all human activity for an entire year this is an absolutely mind-blowing amount of energy freely available for us to harvest and power our planet with minimal environmental impact compared to fossil fuels however solar cells account for less than one percent of global energy production so what's holding us back from using the technology we already have [Music] the transition from fossil fuels to solar cells and other renewables has been a slow process over the last few decades with non-renewables still dominating global energy generation until there is enough political will and renewable energy sources are consistently cheaper than fossil fuel alternatives the world is very unlikely to make a significant enough transition to renewable energy since the price of energy sources varies wildly in different parts of the world it is good to compare a metric called the level of cost of electricity for a region which accounts for the cost of building operating and eventually decommissioning a power source for every kilowatt hour of energy produced in the uk natural gas is the cheapest fossil fuel source and has a levelized cost of 66 pounds per megawatt hour whereas solar cells have a cost of 80 pounds per megawatt-hour however in the us these costs are 36 dollars per megawatt hour and 32 dollars per megawatt hour respectively which is very promising the vast majority of solar cells used today are crystallized silicon these are what we're used to seeing on rooftops and solar farms the price of crystalline silicon solar cells has dropped rapidly since their inception in 1977 and is already becoming competitive with non-renewable energy sources as strong research and engineering efforts continue to drive down prices although while silicon solar cells are making great strides forward they are not without their shortfalls but before discussing these we have to quickly explain some basic solar cell physics solar cells are made from a class of materials called semiconductors in a semiconductor the electrons sit within a region called the valence band when particles of light called photons enter the solar cell some of these electrons can use this energy to jump up to a region called the conduction band the gap between these two regions is called the band gap and is very important for the solar cell's efficiency once an electron is in the conduction band it is free to move and do work on a circuit providing energy silicon solar cells can achieve power conversion efficiencies of up to 26.7 percent for a single crystal cell relatively close to the theoretical maximum of 29.3 percent however this high efficiency can drop off rapidly with small defects or blemishes in the material therefore they have to be processed at extremely high temperatures which makes them very expensive and time consuming to manufacture in fact it is estimated that it would take around 170 years to produce enough silicon solar cells to generate the energy required to power the earth another key problem with silicon solar cells is that they're an indirect bandgap material meaning that each time the material absorbs a photon it also requires a very specific kick in vibrational energy called a phonon at the same time to absorb this photon this is quite an unlikely event at the atomic level so the silicon solar cells must be made very thick to increase the chances of absorption which massively increases the overall cost an alternative to inorganic silicon are organic solar cells which are made from molecules containing different combinations of primarily carbon hydrogen oxygen and nitrogen organic soy cells can be made from liquids in a similar process to die coating or inkjet printing materials like this are known as being solution processable and can be manufactured at very high throughput and at very little cost and even on top of flexible materials further because of the different combinations of molecules we can choose from we can modify the band gap which is very important for achieving higher efficiencies unfortunately organic solar cells in their current development are inefficient and often quite unstable decomposing over time under heat excessive moisture or exposure to uv light however there is a new technology with the potential to combine the best two qualities of inorganic silicon and organic solar cells known as perovskite solar cells periscope solar cells have achieved remarkable growth since their inception a decade ago sharply increasing inefficiency from 3.8 percent to 25.2 percent these are made from a crystal of the form abx-3 where a is any single positively charged inorganic atom or organic molecule such as cesium methyl ammonium or former medinium b is a metal with a two plus charge such as lead tin or germanium and x is a halide ion that is an atom such as iodine bromine or chlorine with a single negative charge generally speaking successful perovskite cells are a combination of an organic a site and inorganic b and x sites combining the best of both worlds when it comes to their material properties perovskites like organic solar cells are solution processable and also very defect tolerant so they can be manufactured at very low temperatures very quickly and can also be printed on flexible materials the two inorganic components of perovskites give it an edge over organic solar cells in development as they allow the material to achieve very high efficiencies unlike silicon solar cells perovskites have a direct band gap behavior which doesn't require a phonon and other useful physical properties allowing solar absorber layers to be very thin due to the different combinations available these solar cells can also have an array of different band gaps this means they can be used in what is called a tandem solar cell in which different solar cells of different band gaps are stacked on top of each other the bigger band gap material sits on top catching the high energy light efficiently and allows the lower energy light to pass through to the lower band gap material silicon perovskite tandems have already achieved 29.1 percent efficiency but are still a developing technology and will likely continue towards a theoretical maximum of around 38 efficiency the combination of all these properties allow for perovskite solar cells to be a very cheap high performance solar cell which could very well drive the paradigm shift from fossil fuels to solar cells in the near future of course we are yet to see perovskites dominating the solar market with cells on our roots and in solar farms so why is this ultimately persecuted solar cells are just two newer technology to be seen in commercial applications yet the vast majority of exciting results throughout this video and in the field in general have been conducted in well-controlled lab experiments with very small solar cells the size of a postage stamp the first main challenge here is to be able to scale up these cells to be large enough for solar panels which poses both a very significant engineering and scientific task the second main challenge is to be able to have these solar cells last for a long time silicon solar cells already last reliably on rooftops for around 30 years developing perovskites that can avoid being broken down by moisture oxygen and uv light is another significant task needed before perovskites will challenge silicon and ultimately fossil fuels a third important challenge is to replace toxic lead from the system as it could be damaging to health this could be replaced by other similar metals such as tin but is also a relatively new research area perovskites are likely to play a significant role in the near future of renewable energy generation and will hopefully be a key component in bringing down the price of solar cells consistently below the price of fossil fuels transform the energy harvesting landscape of our planet massively reducing the anthropogenic contribution to climate change we'd love to explore other topics in renewable energy and climate science so please leave a comment on what topic you'd like to see next subscribe and click the bell icon to be notified of our future videos on these topics please also check out our other social media and as always look after yourselves each other and most importantly the planet around you thanks again are eden

Channel: OurEden

Views: 75,022

Keywords: perovskite solar cells, perovskite solar panels, perovskite solar, perovskite structure, perovskite solar cells 2022, perovskite solar panels 2022, perovskite crystal structure, perovskite materials, energy, perovskite, perovskite solar cell, perovskites, renewable energy, solar, solar cell, solar energy, solar energy explained, solar panels, solar power, undecided with matt ferrell

Id: KJsaQQkOlM4

Length: 7min 30sec (450 seconds)

Published: Sat Jul 18 2020