In a major step toward bringing transparent solar cells to home windows, researchers at the University of Michigan have developed a method of manufacturing semi-transparent and highly efficient solar cells.
Looking through the semi-transparent solar cells, the cherries on the tree are clearly defined. The new manufacturing process could allow meters-scale electricity production windows. Image credit: Xinjing Huang, Optoelectronic Materials and Components Group, University of Michigan.
“In principle, we can now scale semi-transparently organic solar cells to two meters by two meters, bringing our windows much closer to reality,” Stephen ForrestProfessor of Electrical Engineering at Peter A. Franken University and corresponding author of a study published in the journal Joule.
Traditional silicon-based solar cells are not transparent at all, work for solar farms and rooftops but would defeat the purpose of windows. However, organic solar cells, where the light absorber is a plastic, can be transparent.
Organic solar cells have lagged behind their silicon-based cousins for power production purposes due to technical challenges such as low efficiency and short lifespan. However, recent work in Forrest’s lab has achieved a record efficiency of 10% and an estimated lifespan of up to 30 years.
So the team focused on making transparent solar cells that can be manufactured. A significant challenge is creating micrometer-scale electrical connections between the individual cells that comprise the solar module. Conventional methods that use lasers to shape cells can easily damage organic light absorbers.
Instead, the team developed a multi-step prototyping method to achieve resolution at the micrometer scale. They deposit thin plastic films and form extremely thin bands. Then they settle into organic and metallic layers. Next, they peeled off the bands, creating very fine electrical bonds between the cells.
The new manufacturing process could allow meters-scale electricity production windows. Top: Schematic illustration of the dissection prototyping process. Bottom left: Microscopic image of a light-absorbing semiconductor film on a glass substrate, imaged by peeling off a 10 μm wide polyimide (PI) strip. Bottom right: Photo of the prototype module. Image credit: Xinjing Huang, Optoelectronic Materials and Components Group, University of Michigan.
The team connected eight semi-transparent solar cells, 4 cm x 0.4 cm each and separated by connections 200µm wide, to create a single 13 cm panel2 module. The 7.3% energy conversion efficiency is about 10% lower than the individual solar cells in the module.
This small efficiency loss does not increase with the size of the module; so the same effect is expected for meter-scale plates. With almost 50% transparency and green color, the tiles are suitable for use in commercial windows. This same technology easily achieves higher transparency which can be favored for the residential market.
“The time has come for industry engagement to turn this technology into valuable applications,” said Xinjing Huang, a PhD student in applied physics at UM and first author of the published study. affordable.
Xinjing Huang, a PhD student in applied physics, demonstrates semi-transparent vision through solar cells. The new manufacturing process could allow meters-scale electricity production windows. Image credit: Silvia Cardarelli, Electrical and Computer Engineering, University of Michigan.
Finally, the flexible solar panel will be sandwiched between two window panes. These energy generating films aim to be around 50% transparent with 10%-15% efficiency. Forrest believes this can be achieved within a few years.
“The research we are doing is mocking the technology so that manufacturers can make the necessary investments to go into large-scale production,” Forrest said.
He says the technique could also be common to other organic electronics. And in fact, his team has already applied it to OLEDs for white lighting.
The University of Michigan has applied for a patent and is looking for partners to bring the technology to market.
Source: University of Michigan
