Researchers at Oxford University and Exciton Science have demonstrated a new way to create stable perovskite solar cells, with fewer defects and the potential to finally rival silicon's durability.
From: ARC
Centre of Excellence in Exciton Science
December 7, 2022 -- By removing the solvent
dimethyl-sulfoxide and introducing dimethylammonium chloride as a
crystallisation agent, the researchers were able to better control the
intermediate phases of the perovskite crystallisation process, leading to thin
films of greater quality, with reduced defects and enhanced stability.
Large groups of up to 138 sample devices were then
subjected to a rigorous accelerated ageing and testing process at high
temperatures and in real-world conditions.
Formamidinium-caesium perovskite solar cells created
using the new synthesis process significantly outperformed the control group
and demonstrated resistance to thermal, humidity and light degradation.
This is a strong step forward to matching commercial
silicon's stability and makes perovskite-silicon tandem devices a much more
realistic candidate for becoming the dominant next-generation solar cell.
Led by Professor Henry Snaith (Oxford University)
and Professor Udo Bach (Monash University), the work has been published in the
journal Nature Materials and is available here.
Oxford University PhD student Philippe Holzhey, a
Marie Curie Early Stage Researcher and joint first author on the work, said:
"It's really important that people start shifting to realise there is no
value in performance if it's not a stable performance.
"If the device lasts for a day or a week or
something, there's not so much value in it. It has to last for years."
During testing, the best device operated above the
T80 threshold for over 1,400 hours under simulated sunlight at 65°C. T80 is the
time it takes for a solar cell to reduce to 80% of its initial efficiency, a
common benchmark within the research field.
Beyond 1,600 hours, the control device fabricated
using the conventional dimethyl-sulfoxide approach stopped functioning, while
devices fabricated with the new, improved design retained 70% of their original
efficiency, under accelerated aging conditions.
The same degradation study was performed on a group
of devices at the very high temperature of 85°C, with the new cells again
outperforming the control group.
Extrapolating from the data, the researchers
calculated that the new cells age by a factor of 1.7 for each 10°C increase in
the temperature they are exposed to, which is close to the 2-fold increase
expected of commercial silicon devices.
Dr David McMeekin, the corresponding and joint first
author on the paper, was an Australian Centre for Advanced Photovoltaics (ACAP)
Postdoctoral Fellow at Monash University and is now a Marie Skłodowska-Curie
Postdoctoral Fellow at Oxford University.
He said: "I think what separates us from other
studies is that we've done a lot of accelerated aging. We've aged the cells at
65°C and 85°C under the whole light spectrum."
The number of devices used in the study is also
significant, with many other perovskite research projects limited to just one
or two prototypes.
"Most studies only show one curve without any
standard deviation or any kind of statistical approach to determine if this
design is more stable than the other," David added.
The researchers hope their work will encourage a
greater focus on the intermediate phase of perovskite crystallisation as an
important factor in achieving greater stability and commercial viability.
This work was supported by the Stanford Linear
Accelerator Center (SLAC) and the National Renewable Energy Laboratory (NREL).
Background: About Perovskites
Artificially synthesised in laboratory conditions,
semiconductor thin films made up of perovskite compounds are far cheaper to
make than silicon solar cells, with greater flexibility and a tunable band gap.
They emerged unexpectedly in the last decade and
have reached impressive power-conversion efficiencies of over 25%.
However, too much focus has been placed on creating
the most efficient perovskite solar cell, rather than resolving the fundamental
problems inhibiting the material from being used in widespread commercial
applications.
Compared to silicon, perovskites can degrade rapidly
in real world conditions, with exposure to heat and moisture causing damage and
negatively impacting device performance.
Solving these stability issues is the key challenge
for perovskites in their quest to take on, or "boost" silicon via a
tandem architecture and take their place in the commercial photovoltaics
landscape.
https://www.sciencedaily.com/releases/2022/12/221207100948.htm
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