Lead Free Perovskite Solar Cells Predicted.

[NNadir]

The paper to which the title of this post refers is this one: Predicted Lead-Free Perovskites for Solar Cells (Roshan Ali, Guo-Jiao Hou, Zhen-Gang Zhu, Qing-Bo Yan, Qing-Rong Zheng, and Gang Su,*Chem. Mater., 2018, 30 (3), pp 718–728) Excerpts and graphics from the paper "predicting" lead free perovskite solar cells will be below.

First though, I love the title, "...Predicted."

During my whole adult life - I'm not young - I've heard wonderful predictions about solar energy.

This one, from 1976 is my favorite:

In June 1976 the Institute considered that with a conservation program far more modest than that contemplated in this article, the likely range of U.S. primary energy demand in the year 2000 would be about 100-126 quads, with the lower end of the range more probable and end-use energy being about 60-65 quads. And, at the further end of the spectrum, projections for 2000 being considered by the "Demand Panel" of a major U.S. National Research Council study, as of mid-1976, ranged as low as about 54 quads of fuels (plus 16 of solar energy)

(Source: Amory Lovins, Energy Strategy, The Road Not Taken? Foreign Affairs,, October, 1976 pp. 65-95, excerpt on page 76.)

It's my favorite because there is no reference to the report of "The Institute," they are merely evoked. (The Institute in question was the "Institute of Energy Analysis," which I believe was headed by Alvin Weinberg, the chief developer of the Pressurized Water Nuclear Reactor that Amory Lovins has spent a career despising. Lovins has since had a wonderful career "consulting" for companies like SunCor, which is not a solar company but is rather a Canadian Oil Sands company, which (since it pays Lovins) can tout itself as a "sutainable" oil sands company and which is only one of the greasy fossil fuel companies for which the "green" anti-nuke Lovins consults.

The age of doublespeak is hardly limited to that other asshole Trump.

Lovins also predicted in 1980 that nuclear energy would die by 2000 (or else there would be a nuclear war) but that's another story.

Anyway, a "Quad" is quite nearly an exajoule (EJ) - there's 1.055 EJ to a Quad. Lovins was, without citation, claiming that a little birdie told him that he was free to imply that "by 2000" the US would be consuming 54 quads plus, 16 of solar energy, a total of 70 exajoules.

Current US energy consumption is near his predicted lower end in his first unreferenced assertion, roughly 100 exajoules. However the world as a whole, added another 126 exajoules of consumption since 2000 (it's now widely reported to be 2018) to reach a total of 576 exajoules (as of 2016, the last year for which data's been compiled by the International Energy Agency.)

On the entire planet, as of 2016, the commercial solar industry was not producing 10 exajoules of solar energy, never mind 16 in the United States. In fact, solar and wind combined did not, as of 2016 produce 10 exajoules.

The fastest growing source of energy worldwide from 2000 to 2016 was coal, which increased by more than 60 exajoules to 157 exajoules total.

As a result, the concentration of the dangerous fossil fuel waste carbon dioxide has averaged annual increases of just under 2.2 ppm all through the 21st century, after averaging less than roughly 1.3 ppm in the 20th century, beginning with measurements in 1958.

In 1976, when Lovins wrote this appalling garbage, mean carbon dioxide concentrations were 332.04 ppm; in 2017 they were 406.53 ppm.

A prediction: No one now living will ever see a value for the concentration of the dangerous fossil fuel waste carbon dioxide below 400 ppm, and the reason is that there is little hope that any of us will stop lying to ourselves.

Solar energy is the predicted future, and, regrettably, the future will be the same as the past.

So much for "predictions."

Solar energy is also "clean" and "green," except when it's not.

The most efficient solar materials - generating just tons of excitement in the primary scientific literature - is the "perovskite" structured materials.



Let's turn to the cited paper about the latest "solar breakthrough" du jour, and I'm speaking as an old man who used to get excited by "solar breakthroughs" day after day, going back to the time I was thin and had hair, back in the days when Amory Lovins was declared "a genius." - a long time ago

The authors write in the introduction:

The discovery of organic–inorganic halide perovskites, especially, methylammonium lead triiodide, CH3NH3PbI3 (MAPbI3), and formamidinium lead triiodide, HC(NH2)2PbI3 (FAPbI3), as light absorbers has brought a rapid development in photovoltaics (PV) technology.(1-11) These perovskites contain earth-abundant essential elements, making them highly promising for low-cost and large-scale PV applications. In 2009, Kojima et al.(1) for the first time investigated a MAPbI3-based solar cell with power conversion efficiency of 3.8%. Later, Lee et al.(12) and Kim et al.(3) improved the efficiencies remarkably up to 10.9% and 9.7%, respectively. These works arouse a great passion of studying these materials and the techniques to promote the performance and efficiency. The record efficiency for perovskite solar cells now stands at 22.1%,(13) which is somehow comparable to the crystalline silicon, today’s leading PV technology (25.3%)...

...MAPbI3 is a direct-gap semiconductor, with experimental bandgap of 1.55 eV.(18) It has strong and very sharp absorption, almost 25 times higher than that of Si yet better than GaAs.(19-21) They have long-lived photogenerated electrons and holes and have long charge diffusion length.(22-25) Due to the small electron–hole effective masses, the ambipolar transport is high.(26) In MAPbI3, dissipationless absorption and emission of photons were observed, which enable photons to recycle, leading to utilization of photons within the active layer.(27)

We're saved.

Or maybe not. In solar papers it's rare (though less and less unknown) to wonder about how "green" this technology really is. The authors continue:

Another important and serious issue is the presence of lead in these solar cell materials. As PV panels are normally placed in open field or on the roof of houses, their exposure to rainfall is unavoidable. In the presence of rain and moisture, PbI2 degrades as a substance that may cause severe health problems, i.e., from cardiovascular and developmental diseases to neurological and reproductive damages, increasing oxidative stress.(35) Furthermore, lead pollution has serious impacts on soil and water resources, greenhouse gas emissions, and abundance of material inputs.(36-38) To remove the toxicity of Pb in solar cells, one may either develop an effective method of encapsulation and recycling all components of the PV panels at the end of their lifetime or replace Pb by other nontoxic elements in halide perovskites. For the latter one, the Pb-free perovskites should have excellent absorption, having suitable and direct band gaps comparable to MAPbI3. Also the alternative Pb-free perovskite must exist in the range of tolerance factor (0.81–1.11)(39, 40) to ensure the structural stability of the perovskite solar cell.

The authors begin then to evaluate cogeners and other materials that might replace lead.

This is a computational paper utilizing computer modeling to predict what might replace lead, which is proposed to replace among others, the toxic element cadmium, now in use (as a compound with the toxic elements selenium or tellurium) is some "green" and "distributed" solar cells.

Some pretty pictures from the paper, beginning with the evocative opening "eye catcher" graphic:




The lead perovskite structure along with the structures of some computationally evaluated putative perovskite structures:




The caption:

Figure 1. Supercell structure of MAPbI3 is shown from a front view in (a) and a side view in (b). Supercells are shown for MA(Ca0.125Si0.875)I3 in (c), for MA(Ca0.375Si0.625)I3 in (d), and MA(Ca0.5Si0.5)I3 in (e).

One of the issue with these wonderful perovskite solar cells that will save the world someday (we predict) is that they are structurally unstable, as alluded to in the previous text. One of the powerful things that computational chemistry can do is to predict structure, based on thermodynamic parameters such as the enthalpy or free energy. This kind of data has been incorporated into a factor denoted as the "tolerance factor."

It's plotted here:




The caption:

Figure 2. Tolerance factor (t), black in color, represents the perovskite phase stability for all mono- and mixed-replaced materials. The two dotted black lines represent the tolerance factor range. The red curve represents our calculated formation enthalpy. The blue and magenta color triangles represent the previous calculated enthalpy formation values, while the green square represents the experimental formation enthalpy for MAPbI3. Materials below the horizontal red-dotted line show thermodynamic stability.

Next we have a periodic table talking about the elements in the "predicted" solar cells.



The caption:

Figure 3. Pb-replaced (12 in total), unreplaced (due to smaller ionic radii; 17 in total), metallic (30 in total), highly toxic (12 in total), and mixed (Ca/Si, Zn/Si) Pb-replaced elements are tabulated in the periodic table.

A note on this periodic table. Two of the elements identified here as "toxic" are already found in commercial solar cells; they are cadmium and arsenic. Two of the "replacement" elements are also found in solar cells, gallium (Ga) and germanium (Ge). Both of these latter elements are considered "critical elements" meaning that their long term supply is not guaranteed for future generations.

This calls into question the use of the term "renewable" to describe this stuff.

Another element included in solar cells is probably the most threatened element in the periodic table, indium.

Indium, which is an impurity in zinc (and a few other) ores is a constituent of a semiceramic material known as ITO (Indium Tin Oxide) which has the unique property of being both an electric conductor and being transparent. It is widely utilized in all touch screen devices, including (the major use, since the solar industry remains trivial) cell phones.

The following graphic shows that the perovskite solar cells as designed (and modeled here) contain ITO. So much for "renewable," at least so far as these cells are concerned.



The caption:

Figure 4. (a) Schematic structure of the simulated device, with a single layer perovskite. (b) The dielectric function ϵ2 and (c) the absorption efficiency of the simulated device with the active Pb-free perovskite layer of MAPbI3, MAGeI3, and MASnI3.

Some technical stuff, the bandgap width:

Figure 5. Bandgap values of our mixed study MA(Ca/Si)X3 and MA(Zn/Si)X3(where X= I, Br, Cl). The red dotted line (1.3 eV) shows the ideal band gap for a single-junction solar cell according to the Shockley-Queisser theory. The blue dash-dot line (1.8 eV) shows the ideal band gap for the top-cell in tandem solar cells.

Schockley, for a little bit of history, holds the record for being the most racist Nobel Laureate ever, although he is in a three way tie with Phillip Lennard and Johannes Stark for this dubious distinction, with the (dis)honorable runner up being James Watson.

Now the punchline, the "imaginary" part of the diaelectric function:



The caption:

Figure 6. (a) Imaginary part of dielectric function (?2) and (b) Total device absorption efficiencies (single layer) for methylammonium Pb-free triiodides, MACa0.125Si0.875I3, MACa0.375Si0.625I3, MACa0.5Si0.5I3, and MAZn0.5Si0.5I3 in comparison to MAPbI3. The device architecture of solar cell is the same as in Figure 3a.

The imaginary part...

This "imaginary" of course refers to the fact that the function is a complex function, a type of function that appears quite a bit in mathematical physics and mathematical physical chemistry, most notably in quantum mechanics but also in places like cubic equations of state, like for example, the very widely utilized Peng-Robinson equation for real gases. "Imaginary" here refers of course to the square root of -1, which does not exist except that it does exist as an essential mathematical construct for understanding the universe.

But in the solar case, I also insist - although this is not what people want to hear, although I think it is what they should here if they actually give a rat's ass about climate change, not that anyone, right or left actually does - the imaginary part has a deeper meaning.

The solar industry did not work to arrest climate change; it is not working; and it will not work, and the reason is energy to mass ratios.

And these ratios, the requirement for distribution in what will surely prove an irretrievable way is why so called "renewable energy" will never be as clean, as safe nor as sustainable as nuclear energy. There is not enough matter on the planet, and in particular non-toxic matter to make the solar scheme work, and I haven't even touched the other magic touchstone so often evoked with it, the chemistry of chemical batteries.

I suppose on Valentine's day evening, one should expect to hear what one wants to hear, but I'm not a good guy.

I hope you had a pleasant evening nonetheless.

[Vinnie From Indy]

1. WOW! Nice Post!

99% of people will never read this whole post. Brevity is your friend!

Cheers!

[AJT]

2. Any future in fusion rather than fission?

[NNadir]

4. I often attend lectures at the Princeton Plasma Physics lab, usually...

Last edited Thu Feb 15, 2018, 02:10 PM - Edit history (1)

...in connection with the wonderful The Ronald E. Hatcher SCIENCE ON SATURDAY Lecture Series, and occasionally other lectures open to the public.

The Science on Saturday series covers a broad range of topics, but usually every year - I've been going for close to ten years now - one or two lectures are scientific marketing on the benefits and prospects of fusion.

As a fission advocate I've been somewhat skeptical but they have convinced me and I do believe that the money spent on researching fusion is money very well spent, not just as potential source of significant energy, which it may well be someday - but certainly not soon enough to address the immediate problem of climate change - but also because of the basic science implications.

The ITER project being built in France will not produce energy for the grid, but it will show, for the first time, a net energy gain over the energy invested, a critical step that's been a holy grail for more than half a century.

Even after the accomplishment of this important milestone there are huge hurdles to address. One is materials science. The neutrons released by fusion are extremely high energy, an order of magnitude higher than fission neutrons. I was told by one of the scientists there that they have demonstrated materials that maintain integrity to 100 dpa (displacements per atom), but I believe they're tungsten carbide based.

Tungsten is a critical element, one subject to depletion. This said, fusion reactors have a very high energy to mass ratio, the highest known, orders of magnitude higher than fission reactors, and it is possible to imagine that not much tungsten would in fact be required.

Neutrons cannot be steered like charged particles, and they do, with most elements in the periodic table result in induced radioactivity. (However they can also cause long lived radioactive isotopes to be transmuted into much shorter lived radioactive isotopes that rapidly decay into stable isotopes.) Since neutrons cannot be steered, they must be shielded, and shielded in such a way to recover their energy. This is a non-trivial problem.

Much of the energy released by fusion will be, in fact, contained in these neutrons and that has its own set of difficulties. Some will be in the form of helium ions, effectively alpha particles, also at very high energy, although some heavy atoms do produce alpha particles at roughly comparable energies.

This represents the biggest hurdle to fusion to my way of thinking, heat exchange, the conversion of dense amounts of energy into electricity or other forms of energy that can provide useful work. It is an extension of the materials science problem.

Heat exchange issues are the very issues that lead to the trivial, but disastrous in a purely marketing sense, failure at Fukushima.

Although a fusion reactor cannot practically melt down in the sense that a nuclear reactor of historical design can, components can be destroyed in such a way as to incur huge expense. It's not clear how easy it will be to cross that barrier or what the economic implications will be.

The joke about fusion is that it's been twenty years away from practicality for more than half a century. Again, I think this is a reasonable investment nonetheless, the research into seeing if or when it can become a practical source of energy. It has suffered, I think, from being over hyped. Fusion is certainly superior to solar research, since any nuclear system of any type will clearly and unambiguously superior to any diffuse and material intense system, which solar, and to a slightly less, but insufficiently less, wind systems are.

Nevertheless, this is not the cultural decision that has been made worldwide. The decision has been made to sink vast sums of money into solar and wind, more than two trillion dollars in the last ten years, and the results, written in the planetary atmosphere, are trivial and have had no meaningful effect. I am sure that if just ten percent of that money had been invested in fusion energy, with the balance invested in fission, the world would be a better and safer place.

Thanks for asking. I hope you find these comments useful.

[AJT]

7. Thank you. I have been in favor of nuclear power myself.

The only issue I have is the fact that the people who would be building and running the power plants in this country care only about the immediate bottom line. I don't trust corporations to put public safety above profits and the current anti-regulation, anti-government climate in this country is very concerning.

[NNadir]

9. Well, if we don't trust a subset of corporations with nuclear we are therefore trusting them with...

Last edited Thu Feb 15, 2018, 03:51 PM - Edit history (1)

...gas, oil and coal.

It is not reasonable to pay selective attention to safety issues with nuclear while ignoring safety issues with everything else.

The bottom line in my neighboring state, Pennsylvania, is that companies are allowed to frack dangerous natural gas without regard to the future water supplies of humanity forever.

The flowback water being dumped there is more radioactive (from NORM - naturally occurring radioactive materials) than the water in the sea outside Fukushima.

Moreover the radioactivity in the flowback water primarily consists of radium, with a half-life of about 1600 years and in secular equilibrium with 5 highly radioactive daughter products including but not limited to radon gas. The water outside Fukushima, by contrast, contains low levels of Cs-137, with a half-life of 30 years.

Which is more dangerous?

No matter what circumstances in which nuclear is compared with dangerous fossil fuels, including the circumstances concerned with who is managing it, nuclear is safer.

I believe that regulation is a necessary and desirable requirement for all forms of energy, and for that matter, in pharmaceuticals, where I am privileged to work. However regulations need to be wise and well informed.

It is not reasonable to set a criteria for nuclear energy that no one ever over the next ten thousand years ever be injured or harmed when 70 million people are dying each decade from air pollution from fossil fuels and biomass combustion.

I basically support applying a standard of nuclear regulation to dangerous fossil fuels, to wit: I would like a regulation that no fossil fuel by product at a level that might potentially cause a health risk to someone in the next five centuries ever leak out anywhere at any time.

That would settle the score of climate change and air pollution deaths pretty quickly, don't you think?

[AJT]

10. Very good points.

[NeoGreen]

3. OMG...Still pushing the Great Indium Shortage (GIS) meme....

...you never disappoint:

Another element included in solar cells is probably the most threatened element in the periodic table, indium.

the most threatened element in the periodic table

really?!

https://www.democraticunderground.com/1127109508
https://www.democraticunderground.com/112790020


http://www.indium.com/metals/indium/supply/

According to the U.S. Geological Survey statistics, the worldwide output of indium metal has increased 7X since 1980. We believe that this trend will continue and supply will expand to meet demand.

The indium supply has been bolstered by continued improvement in recycling programs. In the rapidly growing LCD market, greater than 85% of non-deposited indium is reclaimed and returned to the supply chain.

https://minerals.usgs.gov/minerals/pubs/commodity/indium/

By 1992, the thin-film application had become the largest end use. The amount of indium consumed is largely a function of worldwide LCD production. Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply.

https://minerals.usgs.gov/minerals/pubs/commodity/indium/mcs-2017-indiu.pdf

The 2016 estimated average free market price of indium was $240 per kilogram. The average monthly price began the year at $255 per kilogram in January and increased slightly during the first 4 months of the year reach ing $262 per kilogram in April, after which the price decreased through September, falling to $218 per kilogram. News sources attributed low prices to an oversupply of indium and depressed demand after the collapse of the Fanya Metal Exchange Co. Ltd. in 2015. As of August 2016, Fanya’s warehouses reportedly held 3,600 metric tons of indium, and no information was available as to when the inventory would be released into the market. Recent cuts in zinc mine production were not thought to have led to similar decreases in indium production because most of the zinc mines that have closed within the past 1 to 2 years were reported to have produced clean concentrates, or concentrates with relatively low levels of minor metals.

Emphasis added.

...but never despair, the obligatory summary and conclusion is that renewable wind and solar energy are bad and that nuclear is nothing but good and beneficial, in fact nuclear is the bestest! evah! or evah! will be, so says mah authoritah!

(cue harp music)
And don't forget kids, the Nuke-Away Faeries will fly by and make all that nasty radio active waste just magically "poof" into the sun, and they will keep all the bad people away from anything nuclear too so there will be no worries what-so-ever in regards to nuclear proliferation or dirty bombs or nuclear accidents that contaminate huge swaths of farmland or water.
(cut harp music)

on) Especially since nuclear has not killed anyone, ever. off)

Oh, and have an obligatorily nice day.

[NNadir]

5. I guess all those links to pop websites invalidate the concern of thousands of scientists, who...

Last edited Thu Feb 15, 2018, 05:19 PM - Edit history (4)

...think otherwise.

If one were not a lazy fool one could simply enter the term "Indium Scarcity" on Google scholar and get more than 9000 links to papers discussing this issue. Here's just two in two seconds.

Nature Materials

[link:https://www.sciencedirect.com/science/article/pii/S0040609009011213|Thin Solid Films
Volume 518, Issue 4, 15 December 2009, Pages 1304-1308]

From the intro:

Recent indium shortages [1] and toxicity issues [2] have led to a strong demand for indium-free
transparent conductive oxides (TCO) with higher resistivity and higher transparence in the visible
light region for various industrial applications including some types of flat panel

Again, the solar industry, after half a century of mindless cheering remains trivial. The entire industry, coupled with the equally useless wind industry assembled at vast expense, doesn't produce 10 exajoules out of the 576 being generated by humanity as of 2016.

Already there is concern among educated people if not low level cheer leaders for the useless and expensive solar industry, about indium shortages. Imagine if, as these assholes keep saying will happen "by 2050" or "by 2030" or "by whenever" that the industry were required to produce 50 of the 576 exajoules.

Sarcasm requires wit, and wit requires intelligence, and the self declared "sarcasm" of anti-nukes in my view doesn't qualify but that's just my opinion.

Of course, my opinion is informed by the planetary atmosphere, since I'm not a cultist who's willing to trash anything and everything for the solar wind fantasy. By contrast, I'm an environmentalist and a humanist. I'm a humanist in the sense that I'm not on the internet handing out horseshit about Elon Musk's cars for billionaires and millionaires, I care about the 3 billion people on this planet who lack access to basic resources like food, water and sanitary facilities.

The supposition that it is necessary for nuclear power to have never killed anyone - a statement that I've never made - if it is not true, and it isn't, does not mean that nuclear energy is inferior to other systems. Deaths from nuclear energy are vastly exceeded by deaths from airline crashes, automobile crashes, heart disease, and in fact, skiing, not that anyone tries to exercise clearly intellectually inadequate self declared "sarcasm" muscles to express the same concern about any of these deaths, since in their twisted ethical system, anyone anywhere can die from anything as long as it doesn't involve radiation.

On average 41.5 deaths per year take place from skiing.

Now, the big point demonstrating the intellectual and moral hollowness of anti-nukes, as I point out continuously when confronted by the tiny intellects of anti-nukes is the seven million people who die each year from air pollution. This happens while the people, who have bet the planetary atmosphere on solar and wind generated their opinions with lazy googling, no realistic research, no education and no deeper thought, whine about Fukushima.

But the fact remains that not using nuclear power kills people.

Again. Air pollution kills seven million people a year. Apparently the shit for brains who sit around all day long posting about the big "tragedy" at Fukushima on their gas and coal powered computers, never open this link, but that's just fine with me, since I already know they don't give a shit:

A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010 (Lancet 2012, 380, 2224–60: For air pollution mortality figures see Table 3, page 2238 and the text on page 2240.)

By the way, the explosion at the Mitsubishi trichlorosilane factory killed people not that anyone in the solar hyping industry that somehow still is offered credibility, this on a planet where CO2 concentrations are now pushing 410 ppm, gives a rat's ass.

This explosion killed outright, instantly more people than Fukushima did, but again, in the twisted moral universe of anti-nukes and their primitive self described "sarcasm," nuclear power, and only nuclear power must be perfect and without risk, or much more dangerous things can kill at will, in vast amounts.

The solar industry is a failure, an expensive and toxic failure, and all the lazy linking in the world won't change that.

Have a nice, obviously obligatorily oblivious day.

[NeoGreen]

6. You should write a book...

...on how to win friends and influence people.

It would be a best seller and likely at least 1000 pages.

[NNadir]

8. There are actually a lot of people with whom I have no interest in influencing nor befriending.

These people are wholly dogmatic, devoid of original thoughts, and just parrot nonsense about the environment as the atmosphere collapses, and tens of millions people die each decade from air pollution.

Neither am I interested in popularity.

If I were interested in being popular, I could post tens of thousands of posts on the internet about how "by 2050" or "by 2075" or "by 2100" solar energy will matter somewhere, just like the tens of thousands of posts over the years that told us we'd be living in a grand renewable fantasy land "by 2020."

We won't be. We aren't. We've never been.

Or I could post some horseshit about some Tuesday in some month in some year, wind energy briefly produced 70% of the electricity in some tiny hellhole somewhere, like say, that offshore oil and gas drilling hellhole Denmark.

Of course, then if I believed this horseshit, I'd be lying to myself and probably neither too bright nor too well informed, and I would expect intelligent and honest people to be disinterested in my friendship.

Popularity is way over rated, and in general, people who seek it for its own sake are short on giving a shit about the world.

I see it all the time.

It's ethically disgusting, but happily for me, I won't have to live too much longer.

This said, I deeply regret all future generations that will suffer enormously because stupid people prattled on about how, for one example, indium supplies are unlimited and will last forever because, um, they're "renewable!!!!!!!!!"

Don't worry, we can get poor people to recycle it, probably in some country like China, or Lagos, or Nigeria where people about whose health we don't give a shit can help us be smugly "green."