Chapter 468: Your perovskite team’s experiment will stop and stop first

After the invigilation is over, Xu Qiu's schoolwork this semester is all over, and then he can devote all his energy to scientific research.
Xu Qiu returned to Caiyi 216 directly, and found that there were not many people in the office.
A few undergraduates have not come here, and there is a high probability that their exams have not yet been completed.
Today is Wednesday of the 19th week. The Department of General Materials will arrange the exam time for major courses such as degree courses very late.
For example, when Xu Qiu took the test of "Nanomaterials" before, the test time was scheduled on Friday of the 20th week, which is theoretically the latest test time for the school.
For some majors, all exams are completed in 19 weeks, which is equivalent to one week more vacation than the materials department.
Duan Yun and Chen Wanqing were not in the office either, they probably went to their respective companies for internships.
Wu Shengnan may be synthesizing in Jiangwan. Recently, she is synthesizing Y series materials in large quantities.
Tian Qing didn't know if she went for the exam or why she went there. In short, she didn't see her shadow either.
Han Jiaying is in the code word liver article.
Mo Wenlin was doing experiments in the Lijian laboratory and continued to prepare laminated devices.
Feifei Wu and Wo Sun, they recently mentioned the efficiency of tin-based two-dimensional perovskite devices to 2%, and they are discussing the next optimization plan.
The new prospective doctoral student, Fan Wentang, sat in Wu Shengnan's seat, reading the literature.
After scanning around, Xu Qiu first walked to Fan Wentang's side and learned about Fan Wentang's situation.
Now the senior sister is not in the laboratory for three days, so Xu Qiu and Han Jiaying often help with the handover of work.
For newcomers like Fan Wentang, the most important thing at this stage is to be familiar with the main experimental operation methods and to read the literature in the field.
As for the experimental operation, Chen Wanqing has taken Fan Wentang through the device preparation process, but because Mo Wenlin has been helping Xu Qiu to make laminated devices recently, it is not his turn to play as a newcomer.
Therefore, Fan Wentang is mainly responsible for the simple task of cleaning the substrates. The first task every day is to wash 24 clean substrates.
In terms of literature reading, because there are enough articles published in the group, Fan Wentang only needs to thoroughly understand the organic photovoltaic related literature in the group, which is enough for him to have a more in-depth understanding of the current development of the field.
After all, the work in the group is almost at the forefront in all sub-fields, and there are two reviews written by Xu Qiu, and you can also understand some history in the field of organic photovoltaics.
For a newcomer, the literature is almost done to this level in the early stage, and the rest can do experiments while reading the latest literature to supplement.
Xu Qiu is quite satisfied with Fan Wentang's recent performance. The other party's scientific research savvy is not low. In many cases, it can get through.
According to the current trend, Xu Qiu estimates that Fan Wentang can start using it as a complete combat power when the school starts next semester.
It's normal. Fan Wentang is a prospective doctoral student after all, which is equivalent to having more than two or three years of work experience.
Moreover, during his master's period, Fan Wentang was able to publish two SCI works, one of which was also a district AFM.
With these academic achievements, Fan Wentang's scientific research capabilities should have exceeded 90% of other master's students.
Of course, the reason why there are more than so many people is mainly related to the expansion of graduate students’ enrollment. As a result, the word
research
in graduate students has become more and more watery. Graduate school for research.
Xu Qiu and Fan Wentang communicated for a while, answered several questions raised by the other party, and then went to Han Jiaying to check the progress of the school girl's writing.
Han Jiaying was writing the description of the photoelectric properties of the PTQ series of materials. Seeing Xu Qiu coming over, she was a little happy and took the initiative to chat.
Then, Xu Qiu found that the school girl's work efficiency plummeted, and she misspelled several words while chatting and typing.
So Xu Qiu and the school girl greeted her, and she didn't bother her anymore.
Xu Qiu went to the Lijian laboratory again to check the progress of Mo Wenlin's experiment.
Mo Wenlin is still groping based on the ideas of Xu Qiu's group meeting. Up to now, two batches of devices have been prepared.
Although the highest efficiency of the device she prepared has surpassed the efficiency record set by the school girl before, there is still a gap of one percentage point from what Xu Qiu found out.
After all, it is reality.
Compared with the simulation laboratory, in addition to the biggest difference in the longer exploration time, there are also differences in the specific experimental sequence.
For example, the corresponding relationship between film thickness and rotation speed, do experiments in reality, do this first if you don't come up.
Instead, it will first find out the best conditions by adjusting the concentration and speed of the solution.
Then supplement the scanning electron microscope, light absorption spectrum characterization, and convert the corresponding relationship between film thickness, rotation speed and concentration.
Then the film thickness of the effective layer under the optimal conditions is obtained, and a two-dimensional map of the device efficiency varying with the film thickness of the bottom cell and the top cell is drawn.
That is to say, in reality, stacking devices are not planned according to the film thickness of the top cell and bottom cell, but according to the solution concentration and rotation speed.
When making the device, I don't know the specific film thickness, but only a rough estimate, which is more experienced.
The main thing is to do experiments in reality, which needs to be considered from the perspective of saving time, but in the simulation laboratory, there is no need for such consideration, how convenient and how to come.
Of course, this is not a very critical issue. Although the expression methods are different, the logic behind it is the same.
Xu Qiu checked Mo Wenlin's experimental plan and found that she had some problems in the optimization range of film thickness.
She made too much reference to the experience of the original ternary bottom cell and binary top cell stack devices.
In fact, the situation is very different after it has developed into a binary bottom cell and a ternary top cell stack device.
For example, in the original ternary bottom cell, the optimal conditions for the binary top cell are 110 nanometers in the top cell and 220 nanometers in the bottom cell.
For the current binary bottom battery, the optimal condition for the ternary top battery is that the thickness of the top battery is 130 nanometers and the thickness of the bottom battery is 190 nanometers.
Deviations in the film thickness of 20-30 nanometers may differ by 1%-2% in terms of device efficiency.
In addition, in reality, the concentration and rotation speed are used as experimental conditions. When the system changes, for example, the binary system is changed to a ternary system, the film thickness obtained at the same concentration and rotation speed will be different from before.
In other words, it seems that the position of PCBM has been moved a bit. In fact, the difference between the two systems before and after is already very large, so the conditions need to be explored again.
The current Karen Mok is equivalent to constantly groping around the edge of the 16% iso-efficiency line, and naturally it is difficult to make a breakthrough.
What Xu Qiu has to do is to guide her to the center of the 16% iso-efficiency line to find the opportunity to break through 17%.
Therefore, Xu Qiu thought for a moment and said,
I combined the EQE curve obtained before and analyzed it with a semi-empirical model. The final conclusion is that you can make the thickness of the top battery thicker and reduce the thickness of the bottom battery. Be thinner. Of course, don’t change the thickness too much."
"Oh, okay," Mo Wenlin nodded, "Then I will try it tomorrow. Now these devices are almost ready for spin coating, and it's almost time for evaporation."
After finishing speaking, Mo Wenlin muttered in her heart: "Semi-empirical models are so NB now, can they really guide specific experiments? I always thought they were telling stories... But since Xu Qiu said, It shouldn't be fooling me."
In fact, Xu Qiu was fooling her, but he wasn't completely fooling her. It's all about giving a more reasonable explanation to his conclusion.
This is equivalent to a known conclusion. To reverse the process, through the external quantum efficiency EQE curve and light absorption, it is indeed possible to calculate the theoretical short-circuit current density.
However, this method is rarely used in reality, because when the amount of data is not sufficient, the EQE curve of each device will be biased, so the previous data is used to estimate the subsequent data, and the results are often inaccurate.
Only people like Xu Qiu who have a lot of experimental data in their hands can make predictions.
After that, Xu Qiu made a WeChat call to Wu Shengnan, and cared about the progress of the postdoctoral sister's experiment.
Then, Xu Qiu learned that Wu Shengnan was still in the process of synthesis, but he could get the final product immediately. The synthesis cycle of Y series materials is not short, usually about ten days.
After strolling around, Xu Qiu cared about the group members, and finally returned to his desk.
These are the tasks Xu Qiu usually does. Since he is the head of the organic photovoltaic team in the group, he needs to understand the work progress of other members from time to time and provide them with guidance at any time to prevent them from going in the wrong direction.
In fact, this is also the responsibility of the instructor of the normal research group.
In the next two days, Xu Qiu continued to perfect the "Science" article.
Although this work has only 2500 words, Xu Qiu can see some points that need to be revised every time he reads it.
Moreover, the system has been changed one after another recently, and it is also necessary to reflect these changes in the article.
Otherwise, it would be embarrassing if a situation like "The efficiency of the report is based on the A system, but the other features in the article are written on the B system".
In fact, like many articles submitted in the group before, even if they are of the AM grade, because the submission is relatively fast and urgent, there are actually more or less loopholes.
At least, if you look closely, one or two language problems can always be found.
Of course, the average researcher will not care about this small problem, as long as it is not as many loopholes as holes in the sieve that affect everyone's reading.
Because everyone knows that when reading this kind of academic literature, including some books, the important thing is the opinions and ideas in the text.
In other words, what they value is the highlights and advantages of the article. As for the small shortcomings of the article, it is enough to selectively ignore it. The key point is whether they can gain from it.
Including Xu Qiu reading some articles published in the top CNS journals, there will be mistakes in the pictures.
However, the others are others, and he is himself. For his first "Science", Xu Qiu still tries to polish it to perfection.
In addition to the article, Xu Qiu also took Mo Wenlin to make a new batch of devices, and once again broke the efficiency of the stacked devices to some extent. However, the actual device performance still lags behind the simulation laboratory a lot.
Now the simulation laboratory has repeated Xu Qiu’s previous results, prepared thousands of devices, and fluctuated the efficiency slightly. At the same time, the simulation experimenters have also learned Xu Qiu’s routines and will spontaneously copy the devices in batches. Repeated experiments have further improved the exploration efficiency of the simulation laboratory.
In the past, a certain condition could be explored to the optimum in a week, but now it may be completed in three or four days.
However, Xu Qiu felt that it was the end of this system.
There is basically no room for further optimization in terms of processing technology.
Unless the material of the effective layer is changed, that is another job.
Of course, 17% is good enough.
At first, Xu Qiu set the target of 15%, and later changed it to 16%, and now it is 17%.
If you continue to sprint 18%, what if you can't make it.
Don't be too greedy. The results now have a great opportunity to publish an article in "Science". It is better to let the results fall into their pockets as soon as possible.
On Friday afternoon, Xu Qiu and Mo Wenlin were preparing devices in the Lijian laboratory.
They plan to finish the device tonight and put it in the vapor deposition chamber for a "boring" day, and wait until Saturday to come over and test the results.
Mo Wenlin said that her batch of devices feels very good, and it is worth surrendering her "virgin overtime."
At this time, Wei Xingsi walked in from the outside and glanced around. If the guided missiles were normal, after locking Xu Qiu's position, he walked quickly towards him: "Xu Qiu, how is the device doing?"
"Now the highest is 16.5%," Xu Qiu replied: "I plan to make another batch today, leave it in a vacuum for half a day, and wait for the test on Saturday."
"Thanks, hard work." After Wei Xingsi finished speaking, he glanced at Wu Feifei in the office outside and said, "Xu Qiu, come with me."
"Okay." Xu Qiu followed Wei Xingsi to the outside office with some doubts.
Wei Xingsi clapped his hands, motioned to everyone in the office to listen to him, and then said:
"That's the case. Sun Wo mentioned at the group meeting that the mixed preparation of organic and perovskite devices will affect the performance of perovskite devices. I think it makes sense."
"But if you think about it the other way around, the use of solvents such as DMF in the preparation of perovskite devices will most likely affect organic devices. After all, they are anti-solvents for each other."
"In this case, because Xu Qiu and the others are sprinting for the high efficiency of organic laminated devices, in the next period of time, Feifei Wu and your perovskite team's experiments will stop for a while and wait for Xu Qiu and the others to increase the efficiency. Besides, what do you think?"
"No problem." Wu Feifei said immediately, and Sun Wo nodded in response.
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"Yes," Wei Xingsi said with satisfaction: "The perovskite experiment will stop for a while. During this time, Feifei Wu, take Sun Wo to write a review together, and give the glove box to the organic photovoltaic team..."
Wei Xingsi turned his head and looked at Xu Qiu: "How about making a batch of devices every day to increase the efficiency by 17% as soon as possible?"
"Um... OK." Xu Qiu nodded.
In fact, Xu Qiu had not considered the idea of ​​letting the organic team monopolize the glove box before.
But as a student, it was a bit bad for him to put it forward. Now Wei Xingsi took the initiative to put it forward, and Wu Feifei and Sun Wo had no objection. Xu Qiu went along and agreed.
As for a batch of devices a day, it can also be done.
For example, the first batch of devices is prepared in the evening of the first day, and the evaporation chamber is "vacuum placed" until the day of the next day, and then the second batch of devices is prepared during the day of the second day, and the performance of the first batch of devices is tested at the same time. Then put the second batch of devices "vacuum" into the day of the third day, so as to reciprocate...
The only problem is that the shaft needs to be rotated, and the work intensity is somewhat high.
However, this is not a big problem. Xu Qiu decided to let himself, Mo Wenlin, and Han Jiaying take turns to conduct experiments.
Three batches in three days, divided, that is, each person makes a batch of devices in three days, and the work intensity is average.
In addition, since the sprint efficiency is needed, the regeneration of the glove box can also be done, and try to do the best in all aspects.
Recently, the oxygen content of the spin-coated glove box is often above 10 ppm, indicating that the internal solvent atmosphere is very strong and needs to be cleaned up.
This may also be a major reason why the performance of Mo Wenlin's devices cannot be improved.
So Xu Qiu suggested: "Let’s have another Saturday."
Wei Xingsi had no opinion: "Yes, you can arrange it."
Therefore, Xu Qiu logged onto the school’s hazardous chemicals ordering website and ordered a bottle of 95%+5% nitrogen-hydrogen mixture at the drug warehouse.
Because steel cylinders are pressure vessels and have a certain degree of danger, they should theoretically be placed in a special steel cylinder cabinet when stored in the laboratory to prevent the cylinder from toppling due to sudden events such as earthquakes, and also to slow down the explosion zone of the steel cylinder. The shock wave coming.
However, the laboratory of Handan Material No. 216 was built a few years ago. At that time, the safety requirements for pressure vessels such as steel cylinder cabinets were not so high, and they were all fixed with temporary straps.
Nowadays, newly-built laboratories basically require the use of steel cylinder cabinets.
For example, when the Jiangwan laboratory is designed, it must be equipped with a cylinder cabinet, and it is also mandatory to use a centralized gas supply method, which is all considered from the perspective of safety.
Speaking of the safety of pressure vessels, there was an undergraduate in the Department of Chemistry of the University of Magic and Technology who had broken his hands because of improper operation of the reactor.
Recently, there have been news reports that the Institute of Chemistry of the Chinese Academy of Sciences also had an accident.
It is said that there is a joint master's degree, a first-year master's degree, and a female. During the autoclave hydrogenation reaction, an explosion occurred during the cooling process, the skull shattered, and she died on the spot...
R.I.P.
Although Xu Qiu had never used an autoclave before, he knew something about it and knew that it was much more dangerous than a steel cylinder.
Cylinders have pressure gauges and pressure relief valves, and the explosion risk has been fully considered in the design, and there are also requirements for service life. Therefore, it is rarely heard that steel cylinders explode spontaneously.
The ordinary hydrothermal kettle does not have a pressure gauge. When the hydrothermal kettle is opened from the outside, it is a Schrodinger’s hydrothermal kettle, which is like a "black hole". No one knows what is inside. Happening.
Therefore, it is usually necessary to allow the hydrothermal kettle to fully cool down for a long enough time to ensure that the internal temperature and pressure return to normal before opening the kettle body.
Xu Qiu did not understand the specific circumstances of the accident that happened to this master student.
The high probability is that the operation of opening the kettle was carried out in advance. As a result, the pressure inside the kettle body was very high, and the lid was directly on the head.
Although the underlying problem may be the result of multiple superpositions, it is mainly due to the general lack of attention to laboratory safety in China.
If, by extension, it is the domestic pursuit of "fastness", or "eager for quick success and instant benefits".
For example, some research groups require that the results must be produced in as long as possible, and the synthesis reaction must be completed within a few days. If it is not done well, it means that the work attitude is not serious.
Because many students have not experienced strong winds and waves, they have committed suicide by jumping off the building after repeated PUA by their instructors. It is very possible to ignore safety in order to keep up with the progress of the experiment.
In fact, in the early days of being poor and white, it is indeed possible to pursue rapid improvement in this kind of brute force, to catch up with the forerunners.
But when domestic scientific research has developed to a certain level, effective management and safety considerations may become key barriers to progress.
Just as many industries can grow wildly at the beginning, when they grow to a certain scale, they must be restrained, otherwise there will be a phenomenon of big tails, including a company that tried to intervene in the banking business, and now it has begun to be sanctioned.
After Xu Qiu placed the order online, about half an hour later, the uncle aspirator from the drug warehouse turned the nitrogen-hydrogen mixed gas cylinder over.
The uncle broke a finger, I don't know why.
However, his method of transporting steel cylinders is very skillful. There is an angle of about 15 degrees between the sides of the cylinder. When the cylinder is rotated, the cylinder will rotate and move forward.
Uncle Aspiration arrived at the door of 216, and Sun Wo went to meet him.
Sun Wo is now the person in charge of the laboratory cylinders.
Because the temporary straps used to fix the cylinders were limited, Sun Wo took out the previously empty cylinder of nitrogen-hydrogen mixture and replaced it with a new cylinder.
In fact, if you look carefully, this method of transporting steel cylinders also has potential safety hazards.
The cylinder must go up to the second floor. It must be up by elevator.
The uncle aspirator is directly holding the cylinder and transporting it with the elevator.
A safer approach is to arrange for two people to transport the cylinder, one person is responsible for transporting the cylinder to the elevator, and then no one comes in, press the button of the corresponding floor, and the other person is upstairs to pick up the cylinder and take it out.
In other words, let the cylinder take the elevator upstairs by itself.
At the same time, during this process, the elevator is temporarily prohibited from being used by other people.
This can avoid unexpected situations.
For example, if a steel cylinder is about to explode in an elevator, there is no room for people to escape, and they can only watch themselves being blown to death.
However, in practice, if you really pay attention to safety, you need to invest a lot of additional costs.
Including the cost of publicity, cultivating the awareness of students and teachers ~EbookFREE.me~ There is also additional labor costs, and it is necessary to hire more aspiring uncles.
In fact, domestic safety education has only been vigorously implemented around 2015. Before, there was not even a compulsory "Laboratory Safety Education" course for graduate students.
Including the control of hazardous chemicals began around 2015, and the purchase of drugs before was bought casually.
Later, it is necessary to go through the school drug warehouse process. Precursor drugs such as acetone need to be reviewed by the department before they can be purchased, and the safety self-inspection form needs to be filled out on a regular basis.
Perhaps this is what China has discovered that the path of barbaric growth before the scientific research circle is no longer suitable for the current situation.
However, the process of reform is always very difficult and will encounter various resistances.
After the introduction of many policies, there is great resistance to their implementation, because they will more or less harm the interests of some people.
But as long as the direction is right, there will always be a day of success.
PS: Please guarantee the monthly pass.