Traditional silicon solar cells have good efficiency and stability, but they are
expensive to make and can only be produced in stiff panels.
Perovskite solar cells, on the other hand, are an intriguing
option.
They are cheap cost, high efficiency, thin, lightweight, and flexible
since they can be printed with inks.
Solar panels may now be made with perovskite sheets that cost only $0.25
(£0.18) per square foot, making the technology commercially viable.
Perovskite solar cells have the allure of higher energy efficiency and faster
production than conventional silicon solar cells.
However, they have lagged behind silicon solar cells in terms of efficiency
and, more significantly, stability, easily degrading in normal environments.
Perovskite solar cells can be rendered inoperable by even a small amount of
extreme weather, making them essentially useless.
As a result, they are less long-lasting than silicon-based counterparts,
which can last up to 25 years or more.
Assuming they could stand up to the task, the Perovskite solar panels may
be the next big thing.
Using only a thin film laid on glass or plastic, these
solar cells convert sunlight into electricity at a rate of around 50% more
efficiently than the market-dominating silicon photovoltaic cells.
It's taken NREL scientists seven years to find the perovskite holy grail, and
the cells have overcome numerous obstacles along the way.
From 3% to 29%, they've improved dramatically.
Silicon cells are 20 percent efficient on average, whereas perovskite cells have gone
from seconds to months in durability.
As NREL's perovskite research chief Joe Berry put it: we're trying to connect
the dots between efficiency, performance, and durability.
Theoretically, yes, but in practice, it's true.
For the commercialization of this technology, NREL established the U.S. Manufacturing
of Advanced Perovskites consortium in 2020, collaborating
with three universities and six thin-film solar companies, the majority of
which are start-ups.
According to companies in those regions, perovskite products are already
being marketed in Europe and China.
An Oxford PV tandem perovskite-silicon cell is expected to go into production this
year; the British business stated this.
Perovskites have the advantage of being simple to produce right out of the
gate.
Inkjet printing or roll-to-roll methods can be used to make solar cells.
Energy Materials Corp., a consortium partner with NREL, is attempting to
retool an outdated plant in Rochester, N.Y., to manufacture perovskite solar
films where Kodak photo film was initially manufactured.
On the other hand, a silicon solar cell needs to be refined under high heat
and then infused with other materials before being cut into wafers and
assembled into a solar panel using industrial milling equipment.
But efficiency is Perovskites' main advantage.
Cadmium telluride and copper indium gallium selenide thin films have had
efficiency levels of 7-18% in the past.
Thin films were thought to be more cost-effective than silicon panels, despite
their lower output.
When silicon cell prices fell from $3.40 per watt in 2008 to
20 cents per watt in 2020, thin films lost any edge they had, and they had to
strategize again.
Perovskites have reached 29 percent efficiency in lab tests with a theoretical
ceiling of 31 percent.
A perovskite-silicon combination might achieve 45
percent efficiency, more than double that of today's solar panels.
The power of perovskites lies in their structure, as they are not an object but
rather a shape, a geometry.
It was Russian mineralogist Lev Perovski, whose study on the crystal
structure of the first perovskite – calcium titanium oxide – was credited with
giving it its name in 1839.
Perovskite is a crystal structure that resembles calcium titanium oxide and is
represented by the chemical formula ABX3.
It's like having a pizza with the crust trimmed, a wood triangle, and a cheese
triangle.
Triangles make up the majority of the shapes.
The so-called metal halide compounds, usually containing lead or tin and
iodine or bromine, are the perovskites of interest.
When the sun shines on certain perovskite compositions, they produce
electrons, according to the findings of the researchers.
To show the simplicity, Schelhas prepared a methyl ammonium lead-iodide
perovskite in an NREL lab and gave a visitor a small vial of it and an artist's
paintbrush, instructing him to apply the solution to a square of glass placed
under a bright light and connected to a voltage meter.
The voltage meter began to fluctuate as the clear solution was brushed
against the glass and dried into a black coating.
It was described as magic coming into life.
To get from high-energy violet to the lowest energy red, there are seven
wavelengths.
Perovskites can harvest a wider range of light, including high-
energy blue photons, whereas silicon can only absorb red light.
Those photons are responsible for the sky's many
shades of hue.
Heat, moisture, and even air can break down the components chemically.
Because the ions in the crystal move and the materials degrade quickly
under certain current flows, they may become electrically unstable.
Improving the packaging and encapsulating of the cell to protect the
perovskites, or developing a more durable compound, which was not a
simple process until recently, are the two main approaches to dealing with
the stability difficulties.
Iron-containing materials, or "ferrocenes," may provide a solution to these
issues.
Researchers from City University of Hong Kong (CityU) were able to
significantly increase the efficiency and stability of perovskite solar cells by
including Imperial-made ferrocenes.
According to Nicholas Long from Imperial College London's Department of
Chemistry, "Silicon cells are efficient but expensive, and we urgently need
new solar energy devices to accelerate the transition to renewable energy.
Stable and efficient perovskite cells could ultimately allow solar energy to be
used in more applications – from powering the developing world to charging
a new generation of wearable devices."
He added that: "Our collaboration with colleagues in Hong Kong was
beautifully serendipitous, arising after I gave a talk about new ferrocene
compounds and met Dr. Zonglong Zhu from CityU, who asked me to send
over some samples.
Within a few months, the CityU team told us the results
were exciting and asked us to send more samples, beginning a research
program that has resulted in perovskite devices that are both more efficient
and more stable."
The 'light-harvesting' layer of solar cell devices is made of perovskite.
Even while silicon-based solar cells have proven
more efficient at converting sunlight into electricity, these devices'
electrons are less "mobile," meaning they are unable to move as easily between
layers of collection and conversion.
In ferrocenes, the iron is sandwiched between carbon rings, which gives the
complex its name.
After Imperial's own Nobel Prize-winning chemist Geoffrey
Wilkinson recognized ferrocene's unique structure in 1952, researchers
around the world continued to study ferrocenes for their unique features.
In this situation, the electron richness of their structure allows them to
transfer electrons more easily from the perovskite layer to the following
layers in the solar cell, increasing the efficiency with which solar energy is
converted to electricity.
Efficiencies of perovskite devices with an additional ferrocene layer of up to
29% have been demonstrated in tests carried out by the CityU team and in
commercial labs, approaching efficiency greater than that of standard silicon
cells.
However, ferrocene-based materials solve more than just this issue.
The Imperial team has also been experimenting
with different chemical groups attached to ferrocene's carbon rings.
After sending various versions of these to the Hong Kong team, developed by Ph.D.
student Stephanie Sheppard, the collaborators uncovered one that considerably
increases the perovskite layers' adhesion to the remainder of the device.
More than 98 percent of their initial efficiency was maintained after 1500
hours of continuous maximum power use, thanks to the additional
attachment power.
The addition of a ferrocene layer has brought these
perovskite devices close to existing international requirements for regular
silicon cells in terms of both efficiency and stability.
For the first time ever, researchers have successfully increased the efficiency
of an inverted perovskite solar cell to 29% and passed the International
Electrotechnical Commission's (IEC) stability test.
The team has patented their invention and hopes to license it so that their
perovskite devices can be commercialized.
Currently, they are working with different ferrocene designs to increase the
devices' performance and stability.
It would be possible to reduce the cost of electricity to less than two cents
per kilowatt-hour if they could create a 30-year-long perovskite module.
We could use perovskites for utility-scale energy
production at that price.
Let's know what you think of the potential of this cheaper solar cell.