| Dec 07, 2022 |
|
|
|
(Nanowerk News) 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.
|
|
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.
|
 |
| Solar cells created using the new mechanism displaying less degradation under long term exposure to heat and light. (Image: Oxford University)
|
|
Led by Professor Henry Snaith (Oxford University) and Professor Udo Bach (Monash University), the work has been published in the journal Nature Materials (“Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells”).
|
|
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.
|
