Chapter 476: A big breakthrough in Y series receptors!

Xu Qiu continued to read the documents sent by Wei Xingsi.
The third area one article comes from Li Dan from the National Center for Nano Science and Technology. Their research team published another "short newsletter" article that also contains only one picture.
Speaking of which, Xu Qiu told Wei Xingsi that this journal was not in Wei's journal search database before.
In addition, if the name of this journal is abbreviated to two letters, it can compete with the abbreviation NC of "Nature Communications"...
Li Dan's research group reported a ternary conjugated copolymer donor material named S1.
The molecular structure of this material is modified on the basis of the PBDB-T reference donor. PBDB-T is a D-A binary copolymer, the D unit is BDT, and the A unit is BDD.
In the case of S1, a second type of A unit is additionally introduced, that is, a thiophene unit substituted with fluorine atoms and ethyl acetate. This thiophene unit connected with two electron withdrawing groups can reduce the HOMO energy level of the donor material.
By changing the ratio of the two A units in the ternary conjugated copolymer molecule, the energy level structure of the donor material can be fine-tuned.
The results show that the introduction of 10% mole fraction of the second type A unit, the obtained donor material has the best device performance.
At this time, the S1 material is combined with the COi8DFIC receptor they previously developed, and the battery device prepared can reach the highest efficiency. This is the binary single junction organic photovoltaic device reported so far, and the efficiency is the closest to Xu Qiu's "Nature· A system of energy articles.
Therefore, Xu Qiu also included the S1 material in his donor material library.
In fact, Xu Qiu's impression of Li Dan's research group is quite deep.
The articles published by the other party are basically on the top, most of which are short "short newsletters" articles, and they are all relatively efficient systems.
In addition, Xu Qiu had never heard of Li Dan in the field of organic photovoltaics before. He speculated that the other party might have transferred from other photovoltaic fields, and then just caught the vent of non-fullerenes and took off directly.
Of course, it may also be because the journals submitted by the other party are relatively "biased", and they cannot be seen by Xu Qiu if they are not in Wei Xingsi's journal library.
The fourth work is an AM article from Ma Weiwei's group.
What they are doing is polymer acceptor materials based on ITIC. The main idea is Xu Qiu's previous review of "Joule" and the idea that they informed them during the exchange conference.
However, the performance of the device they reported is not high, and the efficiency has just exceeded 10%.
Perhaps it is that their device optimization is not very good. Xu Qiu's results of the same system in the simulation laboratory can achieve more than 11% efficiency.
This work can be published on AM. On the one hand, they may have better luck. On the other hand, it may also be because the work is more innovative. After all, it can be regarded as a small subdivision.
In addition, it may also be related to the names Xu Qiu and Wei Xingsi hanging in this article.
There are four authors in this AM article. Ma Weiwei is a four-author plus communication, her master's student is a first-author, Xu Qiu is a second-author, and Wei Xingsi is a third-author.
Among them, Xu Qiu did not participate in the specific experiments of this work, but only helped to make changes before the other party submitted the paper.
However, the experimental idea was put forward by Xu Qiu, and it is not too much for him to make a second work.
Moreover, this is also the rule of the game in the scientific research circle.
Like academics, there are hundreds of articles at every turn, and nearly a thousand articles, many of which are posted by name. It is difficult to publish so many articles on my own research group.
Even for a large research group, it is very rare to be able to stably publish 20 large and small articles a year.
In most cases, the boss actively or passively cooperates with other people, the boss proposes an idea, puts a name, and other people help realize the idea, and finally achieve a win-win situation.
The fifth part of the work, Yan Hu from the University of Hong Kong, they published an AM sub-issue AEM.
Based on the derivative of PCE11 donor, Yan Hu's group synthesized a PBT3T donor molecule similar to Xu Qiu's previous work, and named it PffBX-T3.
After that, they combined the PffBX-T3 donor material with the ITIC2 acceptor material to prepare an organic photovoltaic device with an efficiency of 11.3%.
There is not much highlight of this work, it is based on the modification of the donor material, so it was only published on AEM.
Now the threshold of organic photovoltaic field has been very high by Xu Qiula.
Originally, the 8% efficiency was able to reach the second and the weak one. Now if the novelty is not enough, 10% of the efficiency is needed to get the weak one, and the 11% efficiency can only be published in AM sub-journals.
Of course, this is the standard for purely efficient work.
If there are other highlights, such as Ma Weiwei's article, although the efficiency is lower, it can also be used for AM.
For the sixth work, the Lu Changjun research group of the Institute of Chemistry of the Chinese Academy of Sciences published a JACS.
They reported an organic photovoltaic stacked device with an efficiency of 13.8%.
Most of the materials used are old materials, the bottom battery is the top battery, and the transmission layer material uses zinc oxide. The book is compiled and produced by the public account. Follow VX [Book Friends Base Camp] Reading books and getting cash red envelopes!
Previously, the Forrest research group of the beautiful country also published an article on laminated devices in the field of organic photovoltaics, but on "Nature Photoelectric", the efficiency can reach more than 14%.
In fact, just discussing the level of these two stacked device articles, the JACS of Lu Changjun's group is not much different from the previous Forrest group's "Nature Optoelectronics".
But Lu Changjun and the others only published one JACS, which is still a pity.
There may be many reasons. For example, Lu Changjun's shot speed is a bit slow, and the submission time is later than that of the beautiful country Forrest group; the efficiency has not been broken, and the value of 13.8% is slightly lower than the Forrest group's 14%+; plus Lu Changjun is in The influence in the field of organic photovoltaics is not as good as that of Forrest.
In summary, only one JACS was published.
In addition, it may also be because there is no transitional period between the top journals of a district like JACS and the big journals of
Nature
like
Nature Photoelectric
.
If you can't make it to the big magazines of Nature, you can only fall back to JACS, AM, NC, EES....
Therefore, if some research groups feel that they can't make it up, they won't submit to the "Nature" major journal, because the review of the "Nature" major journal is relatively slow, which is too time-consuming.
In the seventh work, the Choi research group of Kimchi Country published an ACSEL.
They synthesized a donor material called 3MT-Th. The molecular structure of this binary DA copolymer donor material is very simple. The D unit is BDT and the A unit is thiophene substituted with ethyl acetate. It is easier and the cost may be lower.
They combined 3MT-Th donor and IDIC acceptor materials, and used non-halogen solvent toluene for device processing, with an efficiency of up to 10%.
In general, the design idea of ​​this 3MT-Th material is somewhat similar to the PTQ series material that Xu Qiu gave to the school girl before.
It is mainly to highlight the highlight of "simple synthesis and cost saving". In addition, this work also introduces the concept of "non-halogen solvent".
Inspired by this article, Xu Qiu intends to let the school girls try non-halogen solvents in the future. Although the efficiency of the device may not be improved, it can be regarded as a bright spot for nothing.
Seeing this, Xu Qiu found that most of the latest reported articles are based on the synthesis and development of donor materials.
He speculated that it might be because he made too many receptor materials, which made the path other people can walk almost, causing others to choose the path of donor materials one after another.
Of course, it is also possible that the dominant direction of many research groups is the donor direction.
After all, in the previous era under the rule of the fullerene system, the development of acceptor-based materials was thankless, making most researchers engaged in the development of donor materials.
In addition, from a utilitarian point of view, Xu Qiu has now developed very complete receptor materials.
However, donor materials are relatively scarce, and there are many opportunities.
As long as a similar donor material is synthesized by the way and mixed with the benchmark acceptor materials such as ITIC, it is not difficult to get a 10% efficiency.
Once the efficiency can reach 10%, you can basically post an article that is weaker than one area, or even one area.
Articles of this level are very attractive even for full professors.
At the same time, Xu Qiu also found that the scientific sense of smell and reaction speed of domestic colleagues are relatively fast.
Looking around, more than half of the organic photovoltaic field is occupied by domestic researchers.
Of course, this may also be related to the reduction of research funding in the field of organic photovoltaics by the beautiful country.
Including Wei Xingsi's return from the beautiful country, he was actually affected by the beautiful country policy. He had some problems with the operation of the NREL research group.
There are only these seven articles in the first area, and the rest are small articles that are weak in the first or second area.
Now when Xu Qiu reads these small articles with weak zone 1 or zone 2, as long as they are not purely mechanism-related documents, most of the articles can be read in less than a minute.
Just look at the title, summary, and glance at the chart, and you can basically know what kind of work the other party has done.
There are just a few things going back and forth: based on the modification of the donor, the modification of the receptor, the modification of the transmission layer, or playing with some other concepts.
It seems that there is some water, but Xu Qiu, as a practitioner, also knows that this is actually impossible.
At this stage, there is really not much new stuff to explore in the field of organic photovoltaics.
To put it bluntly, the field of organic photovoltaics is still in the development stage. We can only compete purely for efficiency, go to the top journals with high efficiency, and go to the worse journals with low efficiency and not too bright spots.
Only by rushing to a certain level of efficiency can we consider more far-reaching issues.
It's like, people will pursue spiritual satisfaction when they are full.
The field of organic photovoltaics is still in a hungry state. If the efficiency has not been able to break through, the final result is to die, that is, to starve to death.
Only when you are full, for example, when the efficiency exceeds 18% and 20%, you can break your hands with perovskite and silicon-based solar cells. Then, you can consider establishing theoretical models to solve various problems that may be encountered in industrialization.
This is a gradual process.
It is almost impossible to achieve a breakthrough in one fell swoop.
This is not only the case in the field of organic photovoltaics, but other scientific research fields are the same today, even in popular scientific research fields.
Because of the development of science and technology, the areas where breakthroughs are easy to achieve have basically been breakthroughs long ago, and most of the rest are hard-to-eat bones.
Someone said: "Perovskite and graphene, the two major fields feed many researchers", "bird droppings doped with graphene can make its performance better."
The implication is to say: "These two fields are easy to write articles, but also a lot of articles."
What they said does have some truth.
What can be seen is that there are many CNS articles published in these two fields every year, and there are countless top publications such as AM and JACS.
For example, Cao has published 7 articles on "Nature" since he has studied graphene.
But at present, whether it is perovskite or graphene, they are still at the laboratory stage and cannot be industrialized.
In this sense, it is indeed quite watery.
So many top journals have been published, so many scientific research resources have been taken up, but there is no real output at all.
But conversely, if people don't go to the water article, then these two very potential fields will not be able to develop.
Behind the "water" is actually the era of the big bang of science and technology has passed, and the technological progress of human civilization has stagnated, or in other words, the situation of low-speed development.
The technology tree that originally required 100 points to light up may now require 100W points to light up.
Under this circumstance, even if the total ability value of scientific research personnel has been improved with the development of civilization, for example, it has been increased by 100 times, the time taken to light up the science and technology tree is still 100 times the original.
In other words, "water" is just an external manifestation of slow development.
In fact, if you think about it in another way, you can know that whether it is domestic or international, scientists who are standing at the head are most likely to pursue scientific research. If they are really capable of making key breakthroughs, who will Want to go to the water article.
After reading the documents sent by Teacher Wei, Xu Qiu went to the wos website to check some of his own work. It is now February, and the article information should be updated once.
It turns out that the AM article given by PCE11, which is Xu Qiu's first Grand Slam article, has now lost the small flame mark of the hot article, but still retains the highly cited small crown.
This is also normal. After all, the crystallinity of the PCE11 material is too strong, and the compatibility with the fullerene acceptor is not bad, but the compatibility with most non-fullerene systems is not high.
Now the times have changed. The nearly 20-year dominance of fullerenes in the field of organic photovoltaics has ended, and PCE11 has become "the tears of the times."
The AM articles, hot articles and highly cited logos of ITIC receptors all exist, and the number of citations has successfully exceeded 100 times, reaching 168 times, and the number of citations has increased very fast.
This is mainly because the recent non-fullerene-related articles are showing a blowout trend. Just about 30 articles in the first and second areas of SCI were published in this month. If you count the SCI third and fourth areas that Wei Xingsi did not retrieve. The number of articles will only be higher, and may exceed 50 articles.
Most of the articles published in the field of organic photovoltaics are related to ITIC, so I will basically quote Xu Qiu's first ITIC article.
In addition, the ITIC-related "Joule" review and the IDIC-4F receptor "Nature·Energy" article were rated as hot articles and highly cited articles, and received the small flame and small crown logos.
At the same time, the number of real-time citations of these two articles has exceeded double digits, and the growth rate is also very fast.
This is all expected. Now Xu Qiu and Wei Xingsi have become leaders in the field of organic photovoltaics. The published articles are highly likely to be followed and cited by other research groups.
Even if other authors only consider from the perspective of utilitarianism, if they don’t quote Xu Qiu’s article when publishing the article, if the article is sent to Wei Xingsi when the article is reviewed, it will not be embarrassing...
After all, the opinions of different reviewers are different on the journal editor's side. For example, the current Wei Xingsi research group reviews manuscripts in the field of organic photovoltaics. If a rejection opinion is given, the article will basically be cold.
After saving a few new screenshots of Little Flames and Little Crown, Xu Qiu closed the wos web page.
A few days later, a very good news came from the simulation laboratory.
That is, after a series of side chain adjustments, three binary single-knot systems with efficiencies exceeding 17% were finally born.
The corresponding acceptor material names are Y15, Y18, and Y20. The devices prepared by combining them with J4 donor materials have the highest efficiency and the best system efficiency, and even exceed the previous "Science" article stacked devices Specifically, Y15, Y18, and Y20 are all materials obtained by regulating the side chain of Y14.
In the initial Y14 material, the side chain on the TT unit is a linear undecyl group (C11), which is a linear saturated alkane with eleven carbon atoms, and the side chain on the nitrogen atom is 2-ethylhexyl ( EH), which is a branched saturated alkane with 8 carbon atoms.
First of all, Y15 material.
Compared with the Y14 material, it only changes the side chain on the TT unit to a linear nonyl (C9), which is a saturated alkane with nine carbon atoms, and the side chain on the nitrogen atom remains unchanged EH.
The performance of the Y15 system device has been improved slightly. After a simple analysis by Xu Qiu, it was attributed to "shortening the side chain to make the stacking of acceptor molecules easier to achieve, thereby increasing the charge mobility of the material."
Of course, the actual influencing factors are more complicated, and this is a balanced result under the common influence of multiple factors.
For example, Xu Qiu also synthesized Y16 material. Compared with Y15 material, it further reduced the side chain on the TT unit and changed it to a linear heptyl group (C7), which is a saturated alkane with seven carbon atoms. The side chain of EH remains unchanged.
The performance of the device after blending Y16 and J4 materials is only compared with the 16% efficiency of the Y14 system and the 17% efficiency of the Y15 system. The efficiency of the Y16 system has a very large drop.
The reason for the performance shrinkage of Y16 may be that the side chain is too short, which makes it difficult to ensure the solubility of the material. For example, Y14 and Y15 can prepare 15 mg/ml chlorobenzene solution at room temperature, while Y16 needs to be heated to 80 degrees Celsius. Only above can a solution of the same concentration be prepared;
On the other hand, it may be that the side chain is too short, which makes it too easy to stack the molecules. In the GIWAXS results, the crystallization signal of Y16 material is significantly stronger than that of Y14 and Y15. The bulk material achieves effective blending, and the blending morphology is poor.
Secondly, Y18 material.
Compared with the Y14 material, it only changes the side chain on the nitrogen atom, changing it to 2-butyloctyl (BO), which is a branched saturated alkane with 12 carbon atoms, and the side chain on the TT unit Keep C11 unchanged.
DFT simulation analysis results show that the molecular framework of Y14 material has a torsion angle of 15 degrees, and the coplanarity is poor, while the torsion angle of the molecular framework of Y18 material is only 5 degrees.
Therefore, Xu Qiu attributed the improvement of Y18 material performance to "the steric hindrance of the EH side chain on the Y14 material TT unit is relatively large, which makes the Y14 molecular framework poor coplanarity, which affects its charge transport performance."
Finally, Y20 material.
It combines the advantages of Y15 and Y18, changing the side chain on the TT unit to linear nonyl (C9), and the side chain on the nitrogen atom to 2-butyloctyl (BO).
In the end, Y20 material showed a breakthrough in device performance, and a result of 1+1>1.
In addition to Y15, Y18 and Y20, which have successfully entered the 17% club, there are other "failed" Y series materials. For example, the Y16 material just now is an example, directly hitting the street at 12%.
This also shows that the fine control of the side chain is still very critical to the effect of the final device performance of Y series materials.
From this point of view, the control process of Y series materials is very similar to the original control of PCE11 materials, and they are mainly aimed at side chain control.
Xu Qiu immediately found a reason to cite the AM article of PCE11 reasonably.
To be honest, Xu Qiu was a little surprised that the exploration of Y series receptor materials was so smooth during the Chinese New Year.
Think about it when he developed the Y3 material, the efficiency was 14.8%, but he wanted to break through to 15%, just like constipation, he couldn't get up after a long time.
Now, since the Y12 was developed, the efficiency has been directly increased from 15% to 17% in just half a month.
However, it is actually understandable.
Scientific research is the same as diarrhea. As long as you find the key points, it will come out at the beginning, and then it will be much smoother afterwards, like "inspiration gushing out".
Of course, just like Rare always pulls it out, there are limits to improvement.
For example, how to continue this upward breakthrough to 18%, or even higher, is relatively difficult.
Fortunately, Xu Qiu still has a lot of cards in his hand.
In the process of exploring Y series materials, he always locked the donor material to J4 for the convenience of comparison.
Now, he has enriched his donor library through literature reading, and there are many other donor materials to choose from.
Including L2, L6, and S1 materials previously obtained from Zang Chaojun of Qingbei University, Lu Changjun of the Institute of Chemistry of the Chinese Academy of Sciences, and Li Dan of the National Center for Nano Science and Technology, Xu Qiu has developed their current materials and newer materials simultaneously. version.
This approach is a bit like Nanshan Pizza Hut's approach.
For example, the Happy Farm developed by Happy.com at the time, UU Read www.uukanshu.com seemed to be profitable. As a result, Nanshan Pizza Hut also developed a Nanshan Farm for free, and then killed Happy Farm.
However, in scientific research, everyone is for the progress of the entire field, and it is normal to learn from each other's achievements.
The paper is sent out for the reference of others. Otherwise, why should it be published?
Moreover, although Xu Qiu made some modifications on the basis of L2, L6, and S1, such as introducing fluorine atoms, chlorine atoms, etc., but did not change the name of the material, but directly called it L2-Cl, L6 -F Wait, it's better to give the original author face.
Therefore, the next step is to use these new materials to permutate and combine Y15, Y18, and Y20.
In addition, regarding the processing technology, Xu Qiu also has various fine optimization methods, including solvent additives, thermal annealing, solvent annealing, vacuum placement, thermal spin coating, spraying...
After developing so many methods, there is always one that can be used now.
In short, the goal is to hit 18%!