An EU-funded project has pioneered the use of an advanced form of nanotechnology in solar panel manufacturing, laying the foundations for more efficient renewable energy production.
© Ezume Images - Fotolia.com
Solar energy systems will be key to shaping Europe’s energy market in the future as societies turn towards the use of renewables as an alternative to polluting fossil fuels. As such, the need for more efficient solar cells is intense, and one emerging technology studied in the ALD4PV project – led by the Technische Universiteit Eindhoven – is demonstrating important improvements over current production processes.
Atomic layer deposition (ALD), a form of nanotechnology that has been researched most intensely for fabricating nanometre-scale features in computer chips for devices such as smart phones, has only recently emerged as a breakthrough technology for the solar industry, according to ALD4PV project coordinator Erwin Kessels who oversaw work conducted as part of an individual fellowship by researcher Diana Garcia-Alonso Garcia.
“ALD is a method that is highly suited for true interface engineering, which is of vital interest for solar cell manufacturing as the properties of interfaces between different materials play a decisive role in the performance of photovoltaic devices,” Kessels explains.
He says that the ALD4PV project contributed to the wider acceptance of atomic layer deposition by raising awareness of its potential as a relevant and important technique in the manufacturing of solar cells.
Metal-oxide films offer unlimited opportunities
The ALD4PV team explored the use of ALD-synthesised metal-oxide films for different types of solar cells, using the excellent ‘passivation properties’ of aluminium-oxide films for crystalline silicon cells as a starting point. Passivation involves the application of a light coat of a protective material to create a shell against corrosion, which can decrease solar cell efficiency.
By preventing corrosion, these films have been shown to produce efficiency gains of as much as 1 %. That may seem a small gain, but in real-world applications it is a considerable improvement given that the latest generation of commercial solar cells only converts about 20 % of solar energy to electricity despite decades of research. With that in mind, a 1 % gain in efficiency means that a solar panel could produce 5 % more power.
As a nanoscale thin-film technology that is capable of depositing uniform films on complex, three-dimensional objects with atomic precision, ALD reduces the risk of surface defects that can cause efficiency to decrease.
The ALD4PV researchers also studied other materials, such as zinc-oxide films, as a conducting material, and demonstrated a low-temperature ALD process to synthesise platinum nanoparticles that can be used for dye-sensitised solar cells, a type of thin-film solar cell that could be produced more simply and cheaply using the ALD4PV approach.
“Our work demonstrates that ALD offers many opportunities for the solar industry to improve efficiency and production processes, and, most importantly, that the technology is commercially viable,” Kessels says.
Already, after just a few years of research, large-area spatial and batch systems are being implemented that will use ALD to produce next-generation solar cells at an industrial scale, potentially leading to the creation of new companies, projects and jobs focused around applications for the technology.
While most developments are currently focused on the use of aluminium-oxide films in crystalline silicon cells, Kessels foresees many other materials being used commercially in the near future, including doped-zinc oxide, which was prepared for high-volume manufacturing using ALD for the first time as a result of the ALD4PV project.
Significantly, research conducted on ALD for photovoltaics manufacturing is also inspiring other uses of the technology within the renewable energy industry, such as applications in thin-film batteries for energy storage, that are only now starting to be studied.
Kessels expects many more results to emerge from ongoing research triggered by work conducted in ALD4PV and related projects led by the Technische Universiteit Eindhoven, which is on the verge of launching follow-up initiatives under the EU’s Horizon 2020 programme.