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Solar panels are a critical technology in our move towards net zero. Even though we're
seeing a decrease in silicon-based solar panel costs, we haven't seen significant efficiency
improvements ... yet. But what if we could build panels using materials that aren't supply-limited
and with a more straightforward, lower carbon process? As well as achieving higher efficiencies
at the same time? Perovskite solar panels have been promising that future for some time
now, but where are they? And are they the future of solar panel technology? Let's explore
Perovskite solar panels and how they might energize our future. I'm Matt Ferrell ... welcome to Undecided. Solar power is one of the most promising power
sources to reduce carbon emissions. Electricity from photovoltaics into the grid jumped from
597 GWh in 2005 to about 545 TWh in 2018, and with many policies being rolled out to
try and achieve net-zero in the next few decades, solar panel use continues to grow around the
world. Crystalline silicon has been the go-to choice
for decades, and although other materials like copper indium gallium selenide (CIGS)
and cadmium telluride (CdTe) have popped up, they only cover a small piece of the market
-- about 5%. The main reason for that small marketshare is because it's hard to make them
as efficiently and cheaply as traditional silicon-based solar panels. But silicon isn't perfect. It still has issues
regarding cost as well as efficiency, which typically doesn't go above 21% to 22% for
the top selling panels. It's also no secret that making solar panels is a dirty business
due to the intense heat required to remove impurities from silicon, so researchers and
companies have been looking for alternatives. One promising technology that provides simple
manufacturing and highly efficient photovoltaics are perovskite solar cells. Perovskites are a family of materials with
a particular crystal structure discovered by a German scientist, Gustav Rose, when he
was traveling to Russia in 1839. Any type of material that has the same crystal structure
as calcium titanium oxide (CaTiO3) is considered a perovskite. It wasn't until the 1950s that research and
development on oxide perovskites grew up, which included its use in fuel cells, glass-ceramics,
superconducting devices, and more. But it was only in 1999 that perovskites started
being applied to solar cells. Researchers from the National Institute of Advanced Industrial
Science & Technology from Tokyo announced that they've manufactured an optical absorption
layer for a solar cell using a rare-earth-based perovskite compound. After that, the new millennium
came with extensive research on perovskite solar cells, and new fabrication methods and
materials. Perovskites are easy-to-synthetize materials,
and are considered the future of solar cells since their distinctive structure has shown
a great potential for high performance and low production costs. These solar cells have
been improved considerably in a short time frame, with a boom in conversion efficiency
-- from reports of about 3% in 2006 to over 29% today -- going over the maximum efficiency
achieved in traditional mono- and poly-crystalline silicon cells. In laboratories, perovskite cells are manufactured
by spin-coating, spraying or “painting” them onto a substrate, which is a material
that provides the surface for the chemicals to crystalize on. These cells work much like a traditional solar
panel, but for a quick recap... The part of a solar panel that absorbs sunlight
and converts it into electricity is a wafer made of a semiconductor material -- usually
silicon. A semiconductor is a material that usually doesn't conduct electricity well,
unless it's under the right conditions. This is oversimplified, but the cell basically
has two silicon layers. The top layer has a tiny amount of phosphorus, which has more
electrons than silicon. This excess of electrons makes it more negatively charged, so it's
referred to as the N-Type layer. And the bottom layer has a tiny amount of boron, which has
fewer electrons than silicon, to make it more positively charged and known as the P-Type
layer. When a photon of visible spectrum sunlight
hits the panel and is absorbed, it knocks loose an electron while leaving a hole, which
is positively charged. The free electron is attracted to the negatively charged top layer,
while the hole moves down to the positively charged bottom layer. Wires connecting the
top and bottom layers create a circuit for the electrons to reconnect with the holes
... generating electric current. So why does this matter when we're talking
about Perovskites? Today, the mainstream solar technology – silicon
– is reaching its practical efficiency limit when used alone. The physicists William Shockley
and Hans-Joachim Queisser calculated the theoretical maximum efficiency of silicon single junction
solar cells at around 30%. It's known as the Shockley–Queisser limit. Although there
are gains made by multi-junction cells that combine multiple layers and techniques together
as I explained in a previous [video](https://undecidedmf.com/episodes/exploring-solar-panel-efficiency-breakthroughs-in-2020). Another challenge is that silicon also has
to be fairly thick and manufactured with very high heat. But when it comes to Perovskite solar cells,
they don't require the heat and can be manufactured with much thinner layers. They can also work
with almost all visible wavelengths, resulting in a more efficient transport, recombination,
and extraction of charges than silicon cells. Perovskites can be tuned to absorb different
colors in the solar spectrum. This bandgap flexibility opens up another useful application
for these solar cells in high-performance tandem device configurations that achieve
efficiencies above 30%. They can be combined with other materials, like silicon for example,
to form hybrid structures ... those multi-junction cells I mentioned earlier. Each junction,
or group of layers, can be tuned to different wavelengths of light, increasing the over-all
range of wavelengths the entire cell can absorb, which helps with the efficiency. Perovskite can be produced utilizing simple
solutions that don't require expensive, complex equipment and facilities. Its thin-film structure
uses 20-times less materials, and also doesn't require materials that are uncommon or supply
limited. Perovskites are only about half a micron thick while a silicon layer is roughly
200 microns. A life-cycle analysis involving several PV
technologies concluded that producing silicon cells or perovskite-on-silicon tandem cells
results in both a higher carbon footprint and cost compared to multilayer perovskite
cells. Stanford scientists, for example, manufactured
thin films of perovskite with a robotic device with two nozzles. This technique may be able
to produce perovskite modules for $0.25 per square foot, while the cost of traditional
solar panels range from $4 to $10 per square foot. With better efficiencies, cheaper and easier
manufacturing, why aren't we seeing this take over the solar industry? But before I get to that, I’d like to thank
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out for yourself. Link is in the description below. Thanks to Surfshark and to all of you
for supporting the channel. Now back to why we aren't seeing perovskite take over the
industry... The main hurdle for perovskites is whether
they can last as long as silicon panels, which generally come with a 25-year warranty and
last for much longer than that. Perovskites are very sensitive to oxygen,
moisture, and heat, requiring heavy encapsulation to protect the cells, which increases cost
and weight. The most common electrode material in perovskite solar cells right now is gold,
which obviously jacks up the price a little bit, and cheaper alternatives don't last as
long. At warm temperatures, the structures of perovskite cells shift, and although this
change is reversible, it degrades the performance of the cell. Although high efficiencies have been achieved,
like Oxford PV's perovskite-silicon cell, which reached a 29.52% conversion efficiency,
most perovskite firms haven’t published their stability results. They all say that
they follow a certification standard established for silicon solar panels, set by the International
Electrotechnical Commission (IEC). The IEC 61215 standard that the modules are
subjected is composed of a series of accelerated tests to simulate their operation over years.
In one of these tests, the modules are heated up to 85 °C for 1,000 hours at a humidity
level of 85% ... and even bombarded with hailstones. After this heavy and hard series of tests,
if a silicon panel still works, it's assumed that they have a good chance of lasting 25
years. But, in the case of perovskites, even though they could pass these tests, there's
still doubts if in practical conditions they can last all those years due to their instabilities
compared to silicon. We have decades of silicon use in the real world vs. nothing for perovskite
... yet. Microquanta’s perovskite modules, for example,
got the IEC 61215 approval, but it turns out that the modules have their generation capacity
reduced to 80% of their initial performance in 1–2 years on average, according to field
trials in Hangzhou, China. Another small but questionable problem with
perovskite cells is their toxicity. Lead is used in the most common cell structures, and
since it's a toxic metal substance, it needs to be carefully controlled from its manufacturing
to its recycling. While these challenges still exist, a lot
of research and development is being put into making perovskite solar cells a reality. Scientists
and companies are working towards increasing efficiency and stability, as well as increasing
lifespan and replacing toxic materials with safer ones. Researchers from the School of Engineering
at Brown University have recently published advancements to make perovskite solar cells
more durable. First of all, the scientists found which was the weakest interface of perovskites.
Then, they figured out how improve their resistance, which was done with a “molecular glue.” Utilizing this "molecular glue" to glue the
cells together, they increased adherence between the layers of the cells compared to traditional
laboratory adhesives that would have destroyed the cell’s properties. Compared to the commercial perovskite cells
used in this study, which could last about 700 hours, the technology developed by the
researchers boosted the lifespan to 4,000 hours (that’s roughly equivalent to two
years at five peak-sun-hours per day). That's a massive improvement, but the researchers
have identified other areas for improvement, so there's still more to come. Today we have only estimates for perovskite
solar cells, and not too much real world use data. Estimates show that perovskite solar
panels could cost just 10 to 20 cents per Watt, but we still need to wait for this technology
to be commercialized, and mature a little bit, to have a more precise grasp on its true
cost and benefits. And regarding toxicity due to lead, which
is very low by the way, scientists at the Central University of Jharkhand, in India,
have simulated a methylammonium tin iodide perovskite solar cell optimized with a hole
transport layer made of copper oxide (Cu2O). That's a whole bunch of random words ... what
does that even mean? Well, the structure they've created is a lead-free perovskite cell. I
should have probably just ... lead ... with that. Their simulations showed that is has the potential
to reach a power conversion efficiency of 27.43%. And one of the researchers, Basudev
Pradhan, pointed out that costs estimates are about 8-10 times cheaper than standard
silicon-based solar panels. Saule Technologies, one of the leaders in
the perovskite solar cells market, has some really interesting products in the works.
They have a perovskite photovoltaic glass that can be integrated with buildings. It's
a semi-transparent, perovskite solar cell printed onto flexible foils and overlayed
with layers of glass, making it a window that generates electricity. Saule is also producing energy-harvesting
sun-blinds that can block intense summer sunlight, but in the mornings and evenings allow sunlight
to enter the building to provide natural light and passive heating. These blinds can be adjusted
manually or automatically. And the biggest news, in May 2021, Saule launched
the world's first industrial production line of perovskite solar panels in Poland. Jinko Solar, another leader in the solar panel
market, is also working on rolling out perovskite technology. In 2017, the company signed a
non-exclusive deal with Australia-based Greatcell to explore options for commercializing Greatcell's
perovskite cell technology. At its financial statement for the first quarter of 2021 the
Chinese manufacturer pointed out: “We have also completed the construction
of a high-efficiency laminated perovskite cell technology platform that is expected
to reach a breakthrough cell conversion efficiency of over 30% within the year.” So things look like they're finally starting
to heat up. The perovskite solar cell market is estimated to grow at 34.0% CAGR between
2020-2027, but factors such as instabilities and the use of toxic materials could slow
down the growth of the market. Even though companies such as Saule and Jinko
Solar have been investing in this tech, perovskite still has issues to be addressed. But given
that the material’s efficiency has increased from less than 4 percent to over 25 percent
within a decade, it's kind of easy to see why so many people are optimistic about perovskite's
future. Even though efficiency can be a great driver, it'll never spur adoption on its own.
For that it's all going to come down the cost and value ... even if it might not last as
long as silicon. What do you think? Is perovskite going to
take over the market? Jump into the comments and let me know. If you liked this video be
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