Chapter 467: Achieve 17% efficiency, win glory for the country!

In the simulation laboratory, Xu Qiu found that combining the two strategies of "vacuum for a period of time" and "top cell ternary" can indeed achieve the effect of 1+1>1.
However, the highest device efficiency at this stage still has not broken through 17%, only the sum of the increase is not high compared to the previous value.
Xu Qiu guessed it was because of the relatively short groping time.
This kind of groundbreaking exploration work can only be carried out by the Simulation Laboratory III.
In Simulation Lab III, there are only two senior simulation experimenters. Even if they work 24 hours a day, the combined work efficiency is only about ten times that in reality.
For the system of ordinary devices, the simulation laboratory III takes a day or two, which is equivalent to more than ten or twenty days of continuous work in reality, which is enough to explore the conditions more perfect.
However, the exploration of laminated devices is very cumbersome, and it is obviously not enough to give the simulation laboratory a few days.
Having said that, the simulation laboratory has actually done a lot of work, and initially obtained a two-dimensional map of the device efficiency with the thickness of the top cell and the bottom cell.
It's just that the accuracy of this two-dimensional map is not enough, and further experiments are needed to find out the best conditions.
Xu Qiu found two main iso-efficiency lines from the two-dimensional map.
14% iso-efficiency line: Under the condition that the thickness of the top cell is in the range of 90-180 nanometers and the thickness of the bottom cell is in the range of 120-300 nanometers, the efficiency of the laminated device obtained can reach more than 14% in most cases.
16% iso-efficiency line: When the thickness of the top cell is in the range of 120-150 nanometers and the thickness of the bottom cell is in the range of 180-210 nanometers, the efficiency of the device can reach more than 16% in most cases.
In most cases, it is because the iso-efficiency line obtained is not a rectangle, but a shape similar to a triangle.
It is also easy to understand. For example, under the condition of the first 14% iso-efficiency line, two boundary conditions are selected, the thickness of the top cell is 90 nanometers, and the thickness of the bottom cell is 300 nanometers, so the performance of the obtained device will certainly not be very high.
Because the bottom cell is made very thick, it will absorb more light and the short-circuit current density is high, while the top cell is thinner, and the short-circuit current density obtained is small, which is difficult to match the bottom cell, which will cause the device Performance loss.
Therefore, what Xu Qiu has to do now is to find the highest efficiency point in the 16% iso-efficiency line.
He intends to go to battle himself and conduct experiments.
When the simulation experimenters fumbled before, they fumbled with the thickness of 30 nanometers as the interval.
Xu Qiu plans to use 10 nanometers as the precision, so there are 4 grades in the range of 120-150 nanometers for the top cell thickness, and 4 grades for the bottom cell thickness in the range of 180-210 nanometers, which means a total of 44. =16 conditions.
If 3 batches of devices are made under each condition, and each batch is repeated for 3 pieces, a total of 1633=144 pieces, this is too much, and it will never be finished in an hour and a half.
If two batches of devices are made under each condition, and each batch of devices is repeated 2 pieces, a total of 64 pieces, it seems that there are still quite a few.
After thinking for a moment, Xu Qiu decided to continue to lower the standard:
One batch is made for each condition, and each batch of devices is repeated 1 piece, then the total number of devices is reduced to only 16 pieces.
Generally, photovoltaic devices have to be repeated more than 10 batches, but now Xu Qiu doesn't have so much time, so he can only hope that he will be more European, and he will be able to release more than 17%!
Considering that the next experimental work may consume more time, Xu Qiu first returned to reality.
He looked around and found that there was nothing unusual, then adjusted a more comfortable sitting posture and returned to the simulation laboratory.
Then, Xu Qiu opened the simulation laboratory I, which had been sealed for a long time.
With the continuous upgrading of the system, the simulation laboratory I can now open up to 64 times the acceleration function.
However, because the simulation laboratory II and III can automatically hang up, Xu Qiu rarely uses the simulation laboratory I.
But in fact, this function is still very powerful with 64 times acceleration.
For the evaporation operation, it would take one hour of vacuum, but under the condition of 64 times speed, it only takes one minute.
After evaporation, it takes 12 hours, and it only takes 10 minutes to convert at 64 times the speed.
Of course, the consumption of points is also very exaggerated. It takes 6400 points to use for one hour at 64x speed.
Fortunately, Xu Qiu now has a lot of remaining points, with more than 20 W, which is enough for him to squander.
In addition to speeding up in Simulation Lab I, there are many other additional benefits.
On the one hand, the substrate does not need to be cleaned.
Moreover, recently, because of the production of laminated devices, the current substrates have been spin-coated with the two transfer layers for laminated devices, zinc oxide and PFN-Br, in accordance with the best conditions.
Therefore, spin coating can be started directly from the effective layer of the bottom cell, thereby saving a lot of time.
On the other hand, simulation experimenters have passed several spin-coating experiments, combined with light absorption spectrometer, scanning electron microscope and other means, to obtain the corresponding relationship between spin-coating speed and film thickness.
Xu Qiu can spin coating directly at the specified speed to get the corresponding film thickness, without repeating explorations by himself, which also saves a lot of time.
Ready to start the experiment.
Xu Qiu took the substrate with the two-layer transmission layer spin-coated, and first started spin-coating different thicknesses as the effective layer of the bottom battery.
In the process of spin coating, it cannot be accelerated 64 times in the whole process.
For example, the process of picking up the substrate must be accelerated at a normal speed or at a low power.
However, when the substrate rotates, it can still be accelerated.
In terms of conversion, it usually takes 2 minutes to spin-coat a piece, but now it takes about 10-15 seconds at 64x speed.
It took less than 5 minutes of real time to finish painting 16 pieces.
Next, Xu Qiu continued to spin-coated M-PEDOT as the third transfer layer, and spin-coated zinc oxide as the fourth transfer layer.
After the two layers are spin-coated, they need to be wiped and annealed.
Although the annealing takes ten to fifteen minutes, because all the substrates can be annealed together, the actual time consumption is negligible under the 64-fold acceleration.
Two-step spin coating, plus wiping and annealing, the total time is about 30 seconds per substrate, and the total consumption is less than 10 minutes.
Xu Qiu continues to spin-coat the effective layer of the top battery. This step is similar to that of the effective layer of the bottom battery, which is also less than 5 minutes.
The last step is vapor deposition of molybdenum trioxide and silver electrodes.
Before the evaporation, Xu Qiu suddenly had an idea. He copied the 16 spin-coated substrates into 10 copies each, and prepared to evaporate 10 times at the same time, so that 10 batches of devices can be obtained.
Although the effective layers of these 10 batches of devices are all the same, because of the differences in the evaporation operation, the effect of the evaporation operation on the performance of the device can be approximately excluded.
Including the subsequent vacuum placement operation, Xu Qiu also plans to replicate multiple devices at the same time, and then explore the impact of different placement times on the performance of the devices.
In this way, although he only made a batch of devices, he has actually completed the repetitive experiments including evaporation and vacuum placement at the same time. There is a greater probability that his device efficiency will fluctuate higher.
This can be regarded as a human advantage. If the simulators in the simulation laboratory operate, they cannot play Xu Qiu's routine. They will only prepare batches of devices step by step.
I just don't know if Xu Qiu has developed this method, whether they will learn it synchronously, it remains to be seen.
Next, Xu Qiu evaporated 10 batches of devices and placed them in a vacuum. Under the acceleration of 64 times, the total time was less than 30 minutes.
All 10 batches of devices were prepared, which took about 45 minutes in total.
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It seems that Xu Qiu made only 16 devices under the initial conditions, but after two replications, the total number of devices has expanded to more than 1,000.
Finally came the exciting test session.
Because of the acceleration, the test is relatively fast.
Basically, after the connection is completed, the result can be obtained in seconds.
Almost an average of 15 seconds can be tested to get a result.
Xu Qiu chose the batch of devices with the best feel during evaporation, and uniformly chose the vacuum storage time condition to be 12 hours.
Open the cabin and test it.
Xu Qiu's strategy is to directly discard the devices whose initial test efficiency is lower than 16.5%.
If it can reach 16.5% for the first time, then give it three scan opportunities, if the performance does not reach 17%, just discard it.
In this way, Xu Qiu successively tested 1# to 12#, a total of 12 devices.
Among them, the best system is 7#, and the highest efficiency is very close to 17%.
At that time, Xu Qiu made an extra exception and gave it a few more opportunities. As a result, the more he tested the lower, he had to give up in the end.
Until the 13th device, Xu Qiu finally got the data with the initial efficiency exceeding 17% for the first time, reaching the position where he replaced the baffle plate, scanning ten data continuously, the highest efficiency was for Xu Qiu to think about it first. 14#, 15#, 16# tested it again and found that there was no other device with an initial efficiency of more than 17%, and then began to specialize in 13#.
The processing condition corresponding to 13# is that the thickness of the top cell is about 130 nanometers and the thickness of the bottom cell is about 190 nanometers.
Xu Qiu found hundreds of "brothers and sisters" on the 13# device for testing.
First of all, it is different evaporation batches, and the other 9 13# devices under the same 12-hour vacuum storage time. After the test, the highest efficiency is increased to the next, which is for the 13# device under the best batch of efficiency. The device under the storage time was tested, and the results showed that the device with the storage time of 16 hours had the best performance, and the final result could be obtained. Xu Qiu took a long breath.
After more than an hour of tossing, he basically did not have a moment to rest, and he focused on high-intensity operations throughout the process.
Xu Qiu's body was hollowed out and entered the state of "sage time".
Fortunately, the results were very good, and a breakthrough was finally made.
Moreover, it is only the result of preliminary exploration. If the amount of data can be increased before, there is still room for further improvement in device performance.
Therefore, the probability of repeating more than 17% efficiency in reality is very high.
Xu Qiu glanced at the time, and there was about 20 minutes before the end of the exam, so he didn't rush out.
He first handed the best conditions of the moment to the simulation experimenters for batch repetition, and then began to take stock of the course of the stacked devices step by step.
In the beginning, the simpler "four-terminal method" laminated device was prepared based on semi-transparent devices. At that time, semi-transparent devices were used in the bottom cell. As a result, it was found that even with thin-layer metal electrodes, the light loss was still very high. The final device The efficiency is always less than 10%, which shows that the "four-terminal method" is not suitable for organic photovoltaic systems.
Therefore, Xu Qiu chose the "two-terminal method" and started to try again. As a result, several systems were tried, and finally the efficiency reached 10%.
Later, after a period of process exploration, Xu Qiu chose two high-efficiency systems. The device efficiency of the bottom cell and the top cell finally exceeded 12%, breaking the world record for laminated devices at that time.
Later, Xu Qiu optimized the device structure of the "two-terminal method" laminated device. Instead of using the middle thin-layer electrode as the charge recombination layer, it was directly replaced by two almost transparent transport layers, which can significantly reduce The light loss of the small top cell device greatly increases the current density of the top cell, and the efficiency jumps to 14%.
Next, Xu Qiu introduced PCBM in China to regulate the light absorption between the top cell and the bottom cell, so that the short-circuit current density of the two can be more easily matched, and the efficiency was successfully rushed to 15%, breaking through the recognition in the field of organic photovoltaics. Of a threshold.
Then, Xu Qiu saw the Y-series receptors in the stacked device, and felt that when designing the stacked device structure, we should not just take the efficiency of the original single junction device as the benchmark, but should take more consideration into it. The fit between the battery and the top cell, so he replaced IDIC-4F with IDIC-M whose light absorption range is biased towards the short-wavelength range, further pushing the device efficiency up a bit, reaching 15.5%.
Then, Xu Qiu tried to find the near-infrared non-fullerene receptor developed by other research groups to replace the -4F used in the original group. As a result, he found that the COi8DFIC developed by the Li Dan research group of the National Nanoscience and Technology Center was different from his own. The system is the best match, and the final efficiency exceeds 16%.
A few days ago, the school girl made a batch of devices on a whim. As a result, the efficiency of the actual devices surpassed the results of the simulation laboratory. After research, it was found that "vacuum placement" can improve the performance of some system devices. Through this strategy, the efficiency was successfully improved. To over 16.5%.
At the same time, Xu Qiu also got inspiration from the ternary article of Li Dan's research group. The PCBM was taken out of the effective layer of the bottom cell and placed in the top cell. Finally, the efficiency of the device was also increased to more than 16.5%.
Now, Xu Qiu has integrated the two strategies of "vacuum placement" and "top cell ternary", and with his own hands, he has finally completed the inventory of the device efficiency. Xu Qiu is very emotional. It is indeed very good to get the current result. not easy.
Even with the system as a big killer, it took more than two months to optimize the stacked device step by step from scratch.
This is Xu Qiu's longest time-consuming job so far.
Calculated based on the work efficiency of the simulation laboratory being ten times that of reality, if converted into real time, the process of exploration may take as long as one or two years.
In fact, this is also CNS-level work, a workload that is generally required.
Unless it is the kind of discovery that opens up new areas, such as "tear graphene with tape" and the like.
But at this stage, it is very difficult to open up this new field.
Even a Nobel-level scientific research leader cannot guarantee that he will be able to open up a new field in his lifetime. This is very lucky.
Therefore, at this stage, they are fighting in the existing field, trying to make a breakthrough in a certain dimension.
The time required for a breakthrough is usually calculated in years.
This is also the difference between CNS and AM. Xu Qiu’s step-by-step optimization process for laminated devices. If you disassemble the development table article, you can send an AM for every step of optimization, and even some can reach the "Nature" Dazi magazine. level.
Now Xu Qiu puts them together, just to impact a CNS.
In addition to the article, Xu Qiu set the world record for organic photovoltaics once again, and was significantly ahead of other international researchers. This is a very milestone event.
Xu Qiu can be regarded as winning glory for the country.
In fact, before 2015, domestic research on photovoltaic energy was very backward.
According to NREL, the National Renewable Energy Laboratory of the beautiful country, various types of photovoltaic efficiency progress maps are issued, including silicon, copper indium gallium selenium, gallium arsenide, cadmium telluride, organic photovoltaics, perovskite and other types of efficiency worlds According to records, less than 10% of the domestic rankings.
Less than 10%, they are all good-sounding terms. If they are not good-sounding, they are almost 0. The names of domestic universities or research institutes are almost invisible on the list...
The majority is NREL itself. They are beautiful country research institutes specializing in photovoltaics and energy. There are a number of departments in them that deal with different fields. Wei Xingsi came out from there before.
In addition, organizations that have been on the list very often include the University of California, Los Angeles, the beautiful country; the University of New South Wales, the Kangaroo Country, UNSW; the Swiss Federal Institute of Technology, Lausanne, EPFL, and so on.
Of course, the statistics of this chart began in 1975, and there are almost no domestic rankings. It is also related to the fact that the domestic scientific research circle has only started to exert force in the past ten years.
At this stage, in addition to organic photovoltaics, including perovskite photovoltaics, the domestic development is also very good, and many breakthroughs have been made, which can be regarded as a two-pronged approach with organic photovoltaics.
At this time, in reality.
Wang Jizeng on the podium has been observing Xu Qiu, and he has naturally heard of Xu Qiu's name.
Not only that, but he often goes to the website of Wei Xingsi's research group to check if Xu Qiu has published any new work recently.
As a result, there are almost new articles coming out every time I read them, and they are all articles above the AM level that I can't ask for.
Therefore, Wang Jizeng is very curious about how this legendary man can publish articles like drinking water?
As a green pepper scholar, the article is a big mountain on their heads.
Especially the green pepper associate professor who has no background like him, whether he can be promoted to professor depends almost entirely on his academic achievements.
I saw Xu Qiu on the list of proctor assistants before, and Wang Jizeng still had a hint of inexplicable feeling.
I wondered if I could take this opportunity to get acquainted with each other and ask about the secret of posting articles, but found that Xu Qiu was very "cold" and sat in the back seat after sending the test papers.
Then, he didn't move.
It's really that kind of motionless.
Wang Jizeng sighed, and sure enough, the success of others is not accidental.
This kind of concentration is not something you can do by yourself.
At this moment, Wang Jizeng suddenly saw Xu Qiu moving, as if he was about to get up.
Then I got up halfway, didn't get up, and sat down again, still making a slight impact.
What are you doing, a special cultivation method?
Sure enough, the big brother's world is different from mortals like me.
On the other hand, Xu Qiu returned to reality from the simulation laboratory and found that he kept sitting for an hour in a continuous movement, and his hips and legs were numb.
I wanted to stand up, but when I was halfway up I found that I couldn't get up, so I sat back again. As a result, I couldn't control the strength and made a "duang" sound. Fortunately, there were no other students around, otherwise I would be embarrassed.
This reminded him of the black history before.
At that time, Xu Qiu entered the simulation laboratory in a squatting state in the bathroom, but returned to reality and found that his leg was numb and almost fell into the pit...
Therefore, if he wants to do experiments in the simulation laboratory for a long time, he will basically choose to enter the simulation laboratory on the bed in the dormitory.
If you are usually outside, you usually just go in and take a look at the result and then run, not staying inside for too long.
After sitting in the seat for a while, Xu Qiu finally returned to normal.
He got up and inspected, and found that the students in this class were all behaved, and there was no cheating.
But think about it carefully, this is a professional elective course, which may not be very difficult.
At the same time, the difficulty of closed-book examination questions is generally relatively low, mainly to prevent students from failing.
On the contrary, because the open-book test can access the information, the teacher will set the difficulty to be higher, otherwise it will be difficult to give scores if all of them are full marks in the end.
In order to distinguish the A file from other files in the open-book test, the teacher must ask a few distinguishable questions when writing the questions. For example, the teacher in "Composite Materials" took out the questions that were not in the PPT that were taught in the class; Or set up a lot of questions on the test paper to screen students who are slower in writing.
Xu Qiu strolled around and finally stepped onto the podium.
He found that looking down from above ~EbookFREE.me~ the angle of view is very clear, almost at a glance, if there is anything unusual about the students below, you can find out at a glance.
Xu Qiu suddenly understood that the cheating phenomenon he could find before could also be found by the invigilator with a high probability, but they chose to "open one eye and close one eye".
After a while, the bell for the end of the exam finally rang again.
Not many people handed in papers in advance for this exam, only three, and the rest were delayed to the end.
Generally speaking, if you have to hand in your papers in advance, it will be done very early, twenty minutes or half an hour in advance.
When the exam is almost over, the invigilator will generally not agree to hand in the papers in advance.
Because it may be messy and affect the teacher's collection of papers, and when binding the test papers, they need to be arranged according to the student number.
If there are too many people who hand in papers in advance, the order is disordered, and manual arrangement is required, which is more troublesome.
PS: Please guarantee the monthly pass.