from Hacker News

Tandem solar cell achieves 32.5 percent efficiency

by quakeguy on 12/19/22, 6:51 PM with 94 comments

• by philipkglass on 12/19/22, 8:10 PM

  Very good! There are more efficient multi-junction solar cells in commercial use, but the existing ones use stacked III-V semiconductors and are very expensive, really only suitable for space applications. This record is for a thin perovskite material solar cell on top of a conventional silicon solar cell. Both materials are inexpensive.

  The main obstacle to commercialization is keeping the perovskite material stable over long periods of operation. This family of materials is more sensitive to water/oxygen/light than silicon itself, but they need to last nearly as long as silicon for cells used in solar farms and rooftop panels.

• by walrus01 on 12/19/22, 8:32 PM

  Extreme efficiencies in STC W per square cm (or meter) are primarily of interest to things where room to mount PV cells is extremely constrained. Such as on satellites. Look at triple junction GaAs based cells used in satellite applications for example.

  There are a large number of research-lab-only PV cells made in the last 10-12 years which greatly exceed 23% but are economically unfeasible or impossible to purchase for ordinary use. Some of this tech does trickle down eventually, however.

  Of more practical real world interest is $ per STC watt for a panel you can buy in a 20-panel pallet load from an ordinary PV wholesaler. Like a figure of $0.28 USD/W for nominally 380W rated 72-cell monocrystalline Si panels for rooftop or ground mount applications. Meaning that a pallet of 20 panels would be somewhere around $2100 to $2200 USD to purchase plus freight.

  In approximately the last 12 years we've seen things go from if you buy a pallet of "cheap" mass market 72-cell panels, you'd get 320W rated per panel (STC rating of about 4.44W per cell), to now being able to buy something that is 380W rated as mentioned above, approximately 5.27W per cell. All under STC measurement conditions which are only a rough approximation of real world sunlight of course. The same panels typically measure 1.99 x 0.99 meters so you can do the math on the improvement in STC W per square meter if mounting space is a limiting factor.

  https://footprinthero.com/standard-test-conditions

• by sfifs on 12/19/22, 11:56 PM

  Very interestingly, this seems similar to the strategy used by plants to absorb energy from sunlight in the red and blue parts of the spectrum with pervoskite absorbing the blue and silicon the green. However there is no indication this is intentional bio mimicry. Do we not have materials which can absorb the middle green part of the spectrum?

• by NextHendrix on 12/20/22, 8:40 AM

  These perovskites are notoriously difficult to deposit at scale in a uniform enough layer to be effective, with small variances causing dramatic drops in efficiency.

  On the cool side, it's theoretically possible to make them translucent (without the silicon substrate ofc) which could make for cool power generating windows in the future.

  On the not so cool side you really don't want the materials anywhere near you or your water table in the event of a panel being damaged. Lead halide perovskites, methylammonium lead iodide, are insanely toxic and a race to the bottom on price if they become widespread could be an environmental disaster waiting to happen.

  Not to take from the achievements described here, but there isn't any mention of it. There is some hope in taking the lead out (tin based perovskites) but that tends to result in a drop in efficiency.

• by hubraumhugo on 12/19/22, 8:52 PM

  Which solar company has the biggest technological advantage and is best positioned for another solar boom? In which one would you invest?

• by 0cf8612b2e1e on 12/19/22, 9:23 PM

  What is the highest efficiency cell used in production plants today? Is that different than used by homeowners?

  Edit: I mean widespread usage. One lone 10kw plant using 30% panels was not my intention.

• by einpoklum on 12/19/22, 8:37 PM

  So, obviously, there's a difference between efficiency in lab settings and efficiency in the field for mass-produced cells. But - this is an impressive achievement for the Silicon + Perovskite technology.

  But I have a question to the more knowledgeable here: The chart in the story shows other technologies which achieve significantly higher efficiency figures:

  https://www.helmholtz-berlin.de/pubbin/news_datei?did=15092

  specifically, multi-junction cells. Why are they faded-out? Are they not practicable to mass produce and deploy? Only usable in limited scenarios?

  ----

  Partial self-answer: According to Wikipedia,

  https://en.wikipedia.org/wiki/Multi-junction_solar_cell

  > As of 2014 multi-junction cells were expensive to produce, using techniques similar to semiconductor device fabrication, usually metalorganic vapour phase epitaxy but on "chip" sizes on the order of centimeters.

• by tinglymintyfrsh on 12/19/22, 10:42 PM

  Where does this fit in the chart and with what symbol(s)?

  https://en.wikipedia.org/wiki/Solar-cell_efficiency

  (The top is 47.1%)

• by martinpw on 12/19/22, 9:00 PM

  I'm curious how this process works. Is it that the researchers are experimenting with different ingredients and seeing what works best? Or do they have a clear idea what sort of structure they want to build and the research complexity is in how to get the various ingredients to assemble into the required structure? Basically wondering how the researchers go about planning a research program and how clear the goals and timelines are.

• by sasacocic on 12/19/22, 8:11 PM

  Anyone know the previous record? Curios how much of an improvement this is.

• by joshspankit on 12/20/22, 2:17 PM

  Can someone please make a website (a wiki?):

  canibuyoneforunderfiftyusd.com

  Personally I’d buy most of the products I upvote on HN, but it’s a gamble whether they even have a retail product at all.

• by transfire on 12/20/22, 12:23 AM

  When will we have cheap 30%+ efficiency that will last 30+ years? That seems to me the tipping point when Solar can become ubiquitous.

• by yieldcrv on 12/19/22, 11:59 PM

  Does this cross any thresholds of utility?

  Not sure what benchmark to be excited about here aside from progress for the sake of progress

• by moloch-hai on 12/20/22, 2:39 AM

  What are those greyed-out traces in the graph that approach 50%?

• by m0rissette on 12/20/22, 7:41 AM

  Wouldn’t 99% be good? Why are we celebrating shitty efficiency?

• by beaned on 12/19/22, 8:17 PM

  More solar cell types than I realized. Why is this one getting a lot of attention now?