Crystal arrangement results in more power from ferroelectric solar cells

From the underlying paper[1], I found this excerpt:

“The photocurrent or the short-circuit current density (JSC) extracted from BTO is around 0.415 μA/cm2. … The JSC value from SBC555 is around 11.03 μA/cm2 and is about 25 times higher than measured in BTO. The open-circuit voltage (VOC) in the case of BTO was found to be around −0.007 V, as opposed to −0.058 V in SBC555.”

Here, BTO is the existing material and SBC555 is the new material from the paper. Multiplying JSC by VOC to get power density , we see that BTO yields 2.9 nW/cm^2, while SBC555 yields 639.74 nW/cm^2.

For reference, according to [2], we have that “typical external parameters of a crystalline silicon solar cell as shown are; Jsc ≈ 35 mA/cm2, Voc up to 0.65 V.” Notice the unit difference of mA/cm^2 here vs uA/cm^2 above. Multiplying these parameters yields 22,750,000 nW/cm^2. So we see that these cells are still approximately 100,000x worse at producing power than the current crystalline silicon cells.

[1] https://advances.sciencemag.org/content/7/23/eabe4206

[2] https://ocw.tudelft.nl/wp-content/uploads/solar_energy_secti...

That is true. The research is good. But the headline, the article itself, and especially this comment by the author

> Our apologies for not making this clear. The photovoltaic effect was increased by 1000 times compared to previous output achieved from cells made of ferroelectric crystals, not from prevailing solar cells made of silicon or other conventional materials.

misleadingly make it seem like they made 1000x progress from the current best.

Even if the bakery employee yelled "What?" at me, I would not hear snark in that. I would probably hear rude, but not snark. I would also be a little less surprised if it was a very busy place and the employee was visibly harried by the commotion. Or if I was just in any store in NYC.

There's a difference between terse and to the point vs being rude. It's not the terse response's fault the recipient cannot tell the difference.

Also, are we using snark as a synonym for rude nowadays? I'm going to need to update my definitions as I was always understanding snark to be sarcasm. I just want to be using the same words as everyone else on the internet so I don't offend. (that was snark).

Edit: actually, if I went to a store and someone asked "how can I help you today dear gentleperson?", I would immediately assume they themselves were being snarky. That's like saying "bless your heart". It's just dripping with snark.

The 1000x efficiency headline is from Figure 4 of the source PDF:

https://advances.sciencemag.org/content/advances/7/23/eabe42...

Units are Amps per miliwatt on the Y axis and electron volts on the X axis. The black BTO line has a minimum of around 1x10^-10 at 2.8 eV, which is the energy of a photon in 450 nm blue light, and the red SBC222 line has a minimum of around 1x10^-7. Yes, the difference between 10^-10 and 10^-7 is 1000x; good job, headline! But no, that's not the key takeaway from the article.

Solar cells have an efficiency curve based on their bandgap and the energy in the incident light. It's theoretically a straight line, and regular silicon cells get pretty close to it, see the figure here:

https://www.pveducation.org/pvcdrom/solar-cell-operation/spe...

Note the units in A/W, not A/mW, also, the research is at a temperature of 77k, the boiling point of liquid nitrogen, while the above plot is close to room temperature. At 450 nm = 2.a silicon cell produces about 0.35 x 10^-3 A/mW, which represents an efficiency of something like 30% in the real world.

This research and that figure 4 plot fundamentally show that conventional barium titanate = BaTiO3 = BTO, produces very little energy from 450 nm light. The researchers fixed this problem with a multilayer cell using strontium titanate, SrTiO3, or STO, then BTO, then calcium titanate, CaTiO3 or CTO, in an STO_2/BTO_2/CTO_2 crystal lattice stack. That's the breakthrough result; they were able to bridge this gap in energy output and take in more wavelengths of visible light.

The actual efficiency of the starting point was about a million times worse than a good silicon cell. There's plenty of room for improvement when you start that low! The end result is still on the order of a thousand times worse than a silicon cell. A production dye-sensitized solar cell today reaches about 10% efficiency, a monocrystaline silicon cell gets about 22%, but the DSSC has potential to be much cheaper to produce, can be flexible, and is not as well understood. This research may help to close that efficiency gap.

From what the article stated, it seems the longest term testing they did was firing a laser at the red widget for 6 months straight and it maintained constant current the entire time