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Scientists Formulate New Method To Create Low-Cost High Efficiency Solar Cells (phys.org)
An anonymous reader quotes a report from Phys.Org: Scientists from the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) believe they've found a winning formula in a new method to fabricate low-cost high-efficiency solar cells. Prof. Yabing Qi and his team from OIST in collaboration with Prof. Shengzhong Liu from Shaanxi Normal University, China, developed the cells using the materials and compounds that mimic the crystalline structure of the naturally occurring mineral perovskite. They describe their technique in a study published in the journal Nature Communications. Perovskite offers a more affordable solution, Prof. Qi says. Perovskite was first used to make solar cells in 2009 by Prof. Tsutomu Miyasaka's research team at Toin University of Yokohama, Japan, and since then it has been rapidly gaining importance. The fabrication method he and his research team have developed produces perovskite solar cells with an efficiency comparable to crystalline silicon cells, but it is potentially much cheaper than making silicon solar cells.
To make the new cells, the researchers coated transparent conductive substrates with perovskite films that absorb sunlight very efficiently. They used a gas-solid reaction-based technique in which the substrate is first coated with a layer of hydrogen lead triiodide incorporated with a small amount of chlorine ions and methylamine gas -- allowing them to reproducibly make large uniform panels, each consisting of multiple solar cells. In developing the method, the scientists realized that making the perovskite layer 1 micron thick increased the working life of the solar cell significantly. In addition, a thicker coating not only boosted the stability of the solar cells but also facilitated the fabrication processes, thereby lowering its production costs. The team is now working on increasing the size of their newly designed solar cell prototype to large commercial-sized panels that can be several feet long. They have reportedly built a working model of their new perovskite solar modules, thanks to funding from OIST's Technology Development and Innovation Center, but "the process of upscaing has reduced the efficiency of the cells from 20% to 15%," reports Phys.Org. "[T]he researchers are optimistic that they will be able to improve the way they work in the coming years and successfully commercialize their use."
To make the new cells, the researchers coated transparent conductive substrates with perovskite films that absorb sunlight very efficiently. They used a gas-solid reaction-based technique in which the substrate is first coated with a layer of hydrogen lead triiodide incorporated with a small amount of chlorine ions and methylamine gas -- allowing them to reproducibly make large uniform panels, each consisting of multiple solar cells. In developing the method, the scientists realized that making the perovskite layer 1 micron thick increased the working life of the solar cell significantly. In addition, a thicker coating not only boosted the stability of the solar cells but also facilitated the fabrication processes, thereby lowering its production costs. The team is now working on increasing the size of their newly designed solar cell prototype to large commercial-sized panels that can be several feet long. They have reportedly built a working model of their new perovskite solar modules, thanks to funding from OIST's Technology Development and Innovation Center, but "the process of upscaing has reduced the efficiency of the cells from 20% to 15%," reports Phys.Org. "[T]he researchers are optimistic that they will be able to improve the way they work in the coming years and successfully commercialize their use."
In developing the method, the scientists realized that making the perovskite layer 1 micron thick increased the working life of the solar cell significantly.
Typical good quality crystalline silicon solar cells lose as much as 1% per year in efficiency, and lose as much as 15% efficiency in the first few months of deployment. This is why a 100 watt panel will typically produce as much as 120 watts for the first month or so, then taper off to 100 watts, then degrade slowly thereafter. This is one of the reason that to meet code, wiring for a solar installation must exceed the specs of the panels by around 20%. Now, my apologies if this isn't perfectly accurate, I've been intentionally hand-wavy as I've been out of the PV world for a bit.
You're still correct on the basic principles, but the figures you give for crystalline silicon cells describe low-quality cells these days. Typical warranties these days are 2-3% degradation in the first year and 0.5%/year thereafter. The vast majority of field data is not public and that that is public suggests that plenty of modules conform to this sort of warranty and plenty don't, but for what it's worth, reinsurance companies (who actually have access to the highest volumes of field data) are willing to take on the risk of underwriting such warranties.
The manufacturing technique described in this article is similar to that of amorphous silicon, and the quoted sentence above glosses over a lot of ifs in the article.
Degradation in amorphous silicon has to do with the structure of the material itself, not the manufacturing process. That said, perovskite does have its own very serious degradation problem -- much worse than amorphous silicon, in fact -- that needs to be solved (or at least improved) before it will become practical as a major energy source. Even if it can be made cheaper than crystalline silicon, it's hard to see it gaining much traction outside of consumer gadgets and specialized short-term applications if the cells die after 5 years. Someone could still make money that way, but it wouldn't address much of our energy demand.
That said, what I've seen of this work is promising because the scientists are at least making an effort to address many of the issues that have to be solved to commercialize perovskite cells. There is increasing attention paid to that, but it seems to me that many researchers still prefer to chase headline-grabbing efficiencies. I wish them luck, but I do firmly believe they will struggle to create a successful commercial product if they don't make some strides on longevity.