EPFL scientists have greatly improved the operational stability of perovskite solar cells by introducing cuprous thiocyanate protected by a thin layer of reduced graphene oxide. Devices lost less than 5% performance when subjected to a crucial accelerated aging test during which they were exposed for more than 1000 hours to full sunlight at 60°C.
Perovskite solar cells (PSCs) can offer high light-conversion efficiency with low manufacturing costs. But to be commercially viable, perovskite films must also be durable and not degrade under solar light over time. EPFL scientists have now greatly improved the operational stability of PSCs, retaining more than 95% of their initial efficiencies of over 20 % under full sunlight illumination at 60oC for more than 1000 hours. The breakthrough, which marks the highest stability for perovskite solar cells, is published in Science.
Challenges of stability
Conventional silicon solar cells have reached a point of maturation, with efficiencies plateauing around 25% and problems of high-cost manufacturing, heavyweight, and rigidity has remained largely unresolved. On the contrary, a relatively new photovoltaic technology based on perovskite solar cells has already achieved more than 22% efficiency.
Given the vast chemical versatility, and the low-cost processability of perovskite materials, the PSCs hold the promise to lead the future of photovoltaic technology by offering cheap, light weight and highly efficient solar cells. But until now, only highly expensive, prototype organic hole-transporting materials (HTMs,selectively transporting positive charges in a solar cell) have been able to achieve power-conversion efficiencies over 20%. And by virtue of their ingredients, these hole-transporting materials adversely affect the long-term operational stability of the PSC.
Therefore, investigating cheap and stable hole transporters that produce equally high efficiencies is in great demand to enable large-scale deployment of perovskite solar cells. Among various inorganic HTMs, cuprous thiocyanate (CuSCN) stands out as a stable, efficient and cheap candidate ($0.5/gr versus $500 /gr for the commonly used spiro-OMeTAD). But previous attempts to use CuSCN as a hole transporter in perovskite solar cells have yielded only moderately stabilized efficiencies and poor device stability, due to problems associated with depositing a high-quality CuSCN layer atop of the perovskite film, as wells as the chemical instability of the CuSCN layer when integrated into a perovskite solar cell.
A stable solution
Now, researchers at Michael Grätzel’s lab at EPFL, in a project led by postdocs Neha Arora and M. Ibrahim Dar, have introduced two new concepts that overcome the major shortcomings of CuSCN-based perovskite solar cells. First, they developed a simple dynamic solution-based method for depositing highly conformal, 60-nm thick CuSCN layers that allows the fabrication of perovskite solar cells with stabilized power-conversion efficiencies exceeding 20%. This is comparable to the efficiencies of the best performing, state-of-the-art spiro-OMeTAD-based perovskite solar cells.
Second, the scientists introduced a thin spacer layer of reduced graphene oxide between the CuSCN and a gold layer. This innovation allowed the perovskite solar cells to achieve excellent operational stability, retaining over 95% of their initial efficiency while operating at a maximum power point for 1000 hours under full-sun illumination at 60 °C. This surpasses even the stability of organic HTM-based perovskite solar cells that are heavily researched and have recently dominated the field.
Structure of ?-CuSCN and cross-sectional SEM micrograph of a complete solar cell (credit: M. Ibrahim Dar/EPFL)
The researchers also discovered that the instability of the perovskite devices originates from the degradation of CuSCN/gold contact during the solar cell’s operation.
“This is a major breakthrough in perovskite solar-cell research and will pave the way for large-scale commercial deployment of this very promising new photovoltaic technology,” says Michael Grätzel. “It will benefit the numerous scientists in the field that have been intensively searching for a material that could replace the currently used, prohibitively expensive organic hole-transporters,” adds M. Ibrahim Dar.
The Latest on: Perovskite solar cell
- Superhero Bacteria Produce Spider Silkon July 10, 2020 at 5:00 am
Scientists have produced spider silk using photosynthetic bacteria, creating the potential for the production of bulk amounts of the useful biomaterial.
- Spider silk made by photosynthetic bacteriaon July 8, 2020 at 4:28 am
Spiders produce amazingly strong and lightweight threads called draglines that are made from silk proteins. Although they can be used to manufacture a number of useful materials, getting enough of the ...
- How spider silk could become a medical marvelon July 8, 2020 at 4:00 am
Spider silk could be genetically modified and used to help control blood clotting, Melbourne scientists have found.
- Scientists discover new group of trapdoor spiders on Australia's eastern coaston July 8, 2020 at 12:53 am
Researchers say the new trapdoor spider group probably remained undiscovered until recently because their burrows are so well disguised by doors made of leaves, twigs and spider silk.
- New hinge-door-building spider discovered on Australia’s east coaston July 7, 2020 at 11:40 pm
A new group of trapdoor spider that builds burrows hidden by doors of leaves and other material has been discovered in Australia ...
- New trapdoor spider group found on coaston July 7, 2020 at 9:23 pm
A new group of spiders that build burrows well-hidden by camouflaged hinge-doors has been discovered in eastern Australia. Researchers say the new trapdoor ...
- Spider silk used to create lenses for imaging human tissueon July 5, 2020 at 12:00 am
In a recent study published in the Journal of Applied Physics, a team of researchers at Tamkang University and National Yang-Ming University in Taiwan have used this silk to creat ...
- New Spider Silk-Based Biocompatible Lenses for Biological Imagingon July 1, 2020 at 7:50 am
Spiders are generally good only for insect control. However, a new study has shown that they are worth more than that.
- Tiny spider silk lenses could take images inside human bodyon July 1, 2020 at 7:11 am
Researchers in Taiwan used spider silk from a daddy long legs to make miniature lenses which could one day improve medical imaging.
- Lenses made with spider silk could help take pictures inside the bodyon June 30, 2020 at 8:29 am
Tiny lenses made out of spider silk and clear resin can produce a special kind of light beam that makes them perfect for taking images of tiny objects like viruses ...
via Google News and Bing News