MATERIALS | PHOTOVOLTAICS
IMAGE: UNIVERSITY OF CORDOBA
Efficiency and stability were simultane- ously demonstrated by maintaining over 84% initial efficiency for 1,000 hours, even in an 85°C heated environment. “We have got closer to
organic solar cell commer- cialisation by proposing the core principle of a solar cell material capable of high-quali- ty, large-area solution process-
ing, said Hae Jung Son of KIST, who led the research. “Follow-up research will enable
Above: The Sunrey project aims to make perovskite solar cells more sustainable, efficient and durable
eco-friendly, self-sufficient energy generation – which is easily applicable to exterior building walls and automobiles and also utilised as an energy source for mobile and IoT devices.” The research was published in Nano Energy.
Scaling up Researchers at the University of Michigan have developed a way to scale up their semi-transparent solar cells.
“In principle, we can now scale these organic solar cells to two meters square, which brings them much closer to reality,” said Stephen Forrest, professor of electrical engineering at the university, and corre- sponding author of a study published in Joule. Silicon-based solar cells are opaque, so can be mounted on a roof but not within a structure such as a window. This is where organic solar cells could be applied. For this reason, the team has looked into how it can scale up the manufacturer of its transparent solar cells. One challenge is to create the micron-scale electrical connections between individual cells that comprise the solar module. Conventional methods using lasers to pattern the cells can easily damage the organic light absorbers. Now, the team has developed a multistep
Right: UCLA has developed transparent solar panels that can be added to a greenhouse roof
‘peel-off’ patterning method that achieves micron- scale resolution. They deposited thin films of plastic and patterned them into very thin strips. Then, they laid down the organic and metal layers. Next, they peeled off the strips – creating very fine electrical interconnections between the cells. The group connected eight semi-transparent solar cells, each 4 cm x 0.4 cm, to create a single 13 cm2
module. The power conversion effciency of
7.3% was around 10% less than for the individual solar cells in the module. With a transparency of around 50% and a greenish tint, the cells can be used in commercial windows. Higher transparencies – needed for the residential market – could also be achieved with the technology, said the researchers. Xinjing Huang, a doctoral student at the univer- sith and co-author of the published paper, said: “It is now time to get industry involved – to turn this technology into affordable applications.” Eventually, the flexible solar cell panel will be sandwiched between two window panes. The goal for these energy-generating window films is to be about 50% transparent with 10-15% efficiency. The researchers believe this can be achieved within a couple of years. The university has applied for a patent and is seeking partners to bring the technology to market.
Plant light Researchers at the University of California Los Angeles have developed solar panels that can be added to a greenhouse roof – and still allow through the light that plants need. Yang Yang, a materials scientist in the school of engineering, leads a team that designed the device. The research is published in a study in Nature Sustainability. Incorporating a layer of L-glutathione – a naturally occurring chemical that is commonly sold as an antioxidant dietary supple- ment – helped to extend solar cell lifetime, improve efficiency, and still allow sunlight to reach plants in a greenhouse prototype. “Organic materials are uniquely suitable for agrivoltaics because of their light-absorption selectivity,” said Yang. “The main drawback that has prevented their widespread use up to now is their lack of stability.” Organic solar cells tend to degrade more quickly because sunlight can cause organic materials to oxidise and lose electrons. The researchers found that an additional layer of L-glutathione prevented the other materials in the solar cell from oxidising, which resulted in the organic cells maintaining more than 80% efficiency after 1,000 hours of continuous use — as opposed
26 FILM & SHEET EXTRUSION | April 2023
www.filmandsheet.com
IMAGE: UCLA
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