[HN Gopher] Chemist pursues answers to why promising solar cell ...
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Chemist pursues answers to why promising solar cell material
quickly degrades
Author : Brajeshwar
Score : 33 points
Date : 2022-06-14 17:20 UTC (2 days ago)
(HTM) web link (techxplore.com)
(TXT) w3m dump (techxplore.com)
| FunnyBadger wrote:
| Here's the simple reason:
|
| First, product lifetime (aka reliability) is dependent on
| activation energy of failure modes - chemical or physical
| reaction processes that degrade the product structure from its
| functional as-designed form to a non-functional failed form. The
| higher the activation energy, the longer the "thing" will last at
| a given temperature or other energy environment.
|
| Second, the activation of failure modes are related to
| generation/formation activation energies as well - in the case of
| chemical failure reactions, it's often the exact same activation
| energy as the formation chemical activation energy. I.e. the
| activation energy of the chemical reactions used to create the
| chemical species.
|
| Perovskite PV involve organic molecules - you can't make them nor
| to they work without these organic chemicals.
|
| And the activation energy of BOTH creating ANY organic molecule
| and as well as the failure activation energy are ALWAYS lower for
| organic reactions than equivalent inorganic chemicals especially
| like silicon and silicon dioxide (silicon PV).
|
| Thus the reliability lifetime of perovskite PV will always be
| shorter than silicon PV. And this is the reliability physics -
| you can't change the laws of physics because it's politically
| correct/desirable.
|
| The very thing that makes organic semiconductors and perovskite
| PVs "exciting" - low energy to produce them - ALSO is exactly
| what causes their reliability problems. Activation energy is the
| barrier to spontaneous chemical or physical reactions and it's
| either the kT thermal tail and/or QM tunneling that cause both
| creation and failure reactions to move forward.
|
| Another way to look at "activation energy" is to look at the
| temperatures at which you manufacture the materials: silicon
| requires temperatures in the range of 400C-600C but the
| temperature ranges for organic materials such as those in the
| perovskite PVs which is closer to 200C-300C.
|
| Thus you use less energy to make them but they are also
| inherently going to have lower reliability - because physics. So
| anyone should know this even without knowing much more. This the
| trivial "back of the envelope" way of predicting that perovskite
| PV will have worse reliability than silicon PV.
|
| BTW I've been involved in semiconductor reliability for 40 years.
| This is reliability 101. Chemists generally do not attend the one
| semiconductor reliability symposium (IEEE IRPS) that deals with
| this subject so I'm guessing they simply don't know much/enough
| about reliability to see this. Or they do and they want to goose
| some funding and papers from the obvious that everyone in the
| semiconductor industry already knows.
| jhallenworld wrote:
| Maybe they need a UV blocking film? It seems to be a thing:
|
| https://onlinelibrary.wiley.com/doi/10.1002/anie.202100218
| abfan1127 wrote:
| how does UV blocking reduce efficiency?
| selimthegrim wrote:
| Takes the material out of optimum operating temperature?
| agumonkey wrote:
| Isn't there a commercial window for non long term perovskite
| films ? if they're so cheap they can be replaced every 5 years
| it could "work".
| nicoburns wrote:
| My understanding is that they are a bit cheaper, but they're
| also a lot more toxic than traditional solar panel materials.
| Perhaps they'll find a niche, or perhaps someone will find a
| game-changing development, but overall they don't seem
| particularly promising to me.
| ncmncm wrote:
| I think the amount of toxin would be much smaller than
| found in, e.g., CdTe panels (8 g/m^2 of Cd), because they
| may be very thin. But maybe less well contained?
|
| (I read claims that a house fire under CdTe panels will not
| make your neighborhood into a superfund site, but don't
| know how to evaluate them. Is the Te on one side and glass
| on the other expected keep the Cd in, even at 1200 C?)
|
| There are good reasons to want perovskite cells to be
| usable. Efficiency can go above 30%, and they are very
| light and flexible. So, it is great that so many people are
| working on the problem. I never read anything about them
| without the person mentioning attempts to improve lifetime.
|
| They might not be so useful in solar farms, but e.g. on
| high-altitude "dwell" drones that don't land, their
| advantages would be decisive. They are already favored for
| those reasons on satellites, where they are free of
| weather. A dwell drone's useful life might not be more than
| a couple of years anyway, if only because it gets obsolete,
| and anyway the motor and batteries wear out.
|
| Anyway the material does seem to have desirable properties
| besides just being cheap to make.
|
| So, thank you Lea and Sarah, and best of luck!
| thereisnospork wrote:
| >Perovskite PV involve organic molecules - you can't make them
| nor to they work without these organic chemicals.
|
| I was under the impression that perovskites were fully
| inorganic? That they may or may not use organic precursors in
| synthesis is irrelevant.
|
| The interesting question[0] is what is the specific nature and
| mechanism of the failure reactions in perovskites, so that they
| may be mitigated or eliminated by alterations to the chemical
| structure of new perovskites. There is nothing trivially
| intrinsic about the class of materials that precludes
| stability.
|
| A good comparative example where a similar problem has been
| reasonably overcome is with oleds, especially those of higher
| wavelength (higher energy photons to kick off negative
| reactions). Yes they might not last as long as an inorganic LED
| but offer other compelling advantages.
|
| [0]That the researchers appear to be at least attempting to
| answer
| Thorondor wrote:
| The most frequently discussed perovskite absorbers for solar
| cells are methylammonium lead trihalides, which are (at least
| partially) organic compounds.
| philipkglass wrote:
| There are mixed organic/inorganic perovskite solar materials
| as well as fully inorganic ones. The ones with an organic
| component were developed earlier and they show higher
| efficiency than all-inorganic ones. It's unfortunate that
| all-inorganic perovskite materials have not attained the same
| efficiency, because they do exhibit more stable performance.
|
| Here's a Department of Energy overview of organic/inorganic
| perovskite materials:
| https://www.energy.gov/eere/solar/perovskite-solar-cells
|
| Here's a recent advance in all-inorganic perovskite PV cells
| from a Korean group: https://www.pv-
| magazine.com/2021/10/22/ambient-processed-ino...
| cma wrote:
| > Thus the reliability lifetime of perovskite PV will always be
| shorter than silicon PV. And this is the reliability physics -
| you can't change the laws of physics because it's politically
| correct/desirable.
|
| The so-called politically correct scientists never claimed they
| are working on making the life longer than silicon pv did they?
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