I Have a Research Support System

Regardless of the reason behind it, since the current device efficiency has exceeded 16%, the external quantum efficiency EQE curve must be tested.

So, Xu Qiu greeted Han Jiaying: "I'm going to turn on EQE's computer, warm it up, and test it later."

"Okay~Senior brother~" Han Jiaying said in a sweet voice. When there were only the two of them present, the school girl would be more relaxed, but when there were many people, she would be more reserved.

After finishing speaking, the junior girl happily hummed a song, "La la la, la la la la, la la la la, la la la la...", obviously very satisfied with the 16% efficiency data she got.

Xu Qiu shook his head with a smile, walked to the experimental bench next to him, and turned on the EQE computer.

Before testing the EQE curve of the sample, it is necessary to connect the line, test the EQE curve of the standard silicon cell, and perform calibration.

In fact, if you want to be lazy, you can only test the EQE curve of the best laminated system later, which saves time.

However, from the perspective of data completeness, it is better to test them all.

Because if you need to use a certain data later, it turns out that you didn’t test it because of laziness, then you may need to redo all the devices of the entire system and test it again.

Moreover, sometimes the required data may not be obtained after making the device once, and it needs to be repeated twice, three times, or even more times.

Especially to publish articles of the "Science" level, the requirements for data integrity are very high, and all original data files need to be uploaded additionally when submitting a manuscript.

However, for articles like the usual AM submission, you don’t need to upload the original data, you only need to upload the text file and supporting information.

Naturally, Xu Qiu did not choose to be lazy, and planned to test all the devices.

The main reason is that now he and his junior are cooperating to conduct experiments, one is responsible for the test of the J-V curve, and the other is responsible for the test of the EQE curve.

The same workload is divided, and the time spent is only 60 to 70% of the original time, and it may take more than an hour to complete.

And now there are still three hours before twelve o'clock in the evening, there must be time in time, there is no need to hurry.

Therefore, Xu Qiu focused on three things.

While operating the EQE computer for testing, while chatting with the school girl, I was thinking about the reason for the abnormally high device efficiency data in my mind.

After thinking about it, Xu Qiu found that there were two main variables.

On the one hand, it is the change of the experimental operator.

Previously, Xu Qiu and Mo Wenlin were mainly responsible for the preparation of laminated devices, but this time it was replaced by Han Jiaying.

Although the school girl was also taught by herself, and the operating habits should not be too different from her own, but Xu Qiu can't completely rule out the possibility of this.

After all, there are more or less differences between people.

However, even if it is really a factor in this regard, it cannot be verified now.

I can only let the school girl come over next week and try to make another batch of devices to see if I can repeat this result.

On the other hand, when Xu Qiu and the others make multilayer devices, they usually calculate the time and test it directly after the evaporation is completed, and there will not be too long a stop in the middle:

If the test can be completed before 5:30 pm, then the test will be done in the afternoon;

If it is too late to complete the test in the afternoon, and the data is in a hurry, then order takeaway and work overtime to get the data out;

If the data is not in a hurry, then delay the start time of evaporation, and arrange the expected completion time of evaporation to after 7:30 in the evening, so that the experiment can be carried out after the break.

In other words, a series of processes such as the preparation and testing of stacked devices are continuous.

But this time, after the school girl evaporated the laminated device at 5:00 p.m., she did not test it immediately, and then let the evaporated device be placed in the vacuum environment of the evaporation cabin for about four hours until At around nine o'clock in the evening, the test began.

In other words, there is a window period of about four hours between the preparation and testing of this batch of devices.

Normally, Xu Qiu wouldn't suspect that it was the reason, but now he really couldn't find the reason, so he could only start thinking about it from the details.

Moreover, organic photovoltaic devices are also quite special, and its effective layer is a multi-phase blended bulk heterojunction structure.

Theoretically, once the device is manufactured, as long as it is not in absolute zero conditions, the morphology of the active layer changes all the time.

Therefore, even if it is the same device, if it is tested at different times, the results obtained will be different.

It's just that people generally don't think about device performance changes on a shorter time scale, and usually store hundreds or thousands of hours to verify the stability of the device.

Because the storage of short-term devices will be affected by too many factors, it is difficult to control.

At this time, Xu Qiu suddenly had an idea and recalled an experiment experience that Tian Qing told him about a year ago when he first joined the research group:

"I evaporated the devices on Friday, put them in the evaporation cabin, and ran over to test them on Sunday. The efficiency of the devices is actually higher than usual..."

Since then, other people in the group have made devices for half a day, or completed a batch in one day;

But Tian Qing had to wait two days, or even three days to complete a batch. Only occasionally when she was interested in experimenting, would she finish the devices within one day.

At that time, Xu Qiu didn't pay too much attention to Tian Qing's explanation, and only thought that she was making excuses for paddling herself.

Thinking about it now, Tian Qing might not have been lying at the time, she had indeed discovered a unique experimental phenomenon.

Moreover, the phenomenon she mentioned may also be universal, for example, it is also applicable to stacked devices.

That is to say, when the devices are prepared, they are not tested immediately, but placed in the vacuum environment in the evaporation chamber for a certain period of time, which may lead to an improvement in device performance.

This variable is easier to verify than the variable of the previous experimenter.

Xu Qiu directly started the operation in the simulation laboratory to explore the device performance of different systems, and the change trend of the storage time in the evaporation chamber after the evaporation is completed.

Among them, the selected systems include various classic binary single-junction systems, PCE10: PCBM, H22: ITIC, etc., as well as the latest stacked systems.

The placement time varies from 0, 1, 3, 6, 9, 12, 18, 24 hours....

Next, move on to testing.

In addition to the efficiency of the first device reaching 16.15%, when the seventh device was measured later, a device with higher efficiency appeared again, reaching 16.24%, surpassing the result of 16.22% in the simulation laboratory.

Moreover, the processing conditions of the seventh device with better performance are not the optimal conditions found in the simulation laboratory.

This is relatively easy to understand. The optimal conditions in the simulation laboratory are actually aimed at Xu Qiu's experimental operations. Now that two new variables have appeared, the optimal conditions will most likely change accordingly.

In the end, Xu Qiu and Han Jiaying worked in the laboratory until 10:50 in the evening, and finally got all the data.

The short-circuit current density obtained by integrating the EQE curve is basically consistent with the result in the J-V curve, and the error is within 5%, indicating that the device performance data is reliable, and the 16% efficiency data is true.

After finishing the experiment, Xu Qiu found that he was not as tired as he had imagined, and felt more energetic, probably because he was working outside the glove box and could sit on a stool for testing.

The junior girl's face was a little red, I don't know if it was because of being tired, or because of being too excited and happy.

Because there is still some time before the opening of the movie, the two chose to rest at 216.

Han Jiaying sat on Xu Qiu's lap and fell into Xu Qiu's arms, like a battery plugged into a charger.

After charging for more than 20 minutes, the junior girl became full of energy again, bounced off Xu Qiu's body, and said cheerfully: "The next stop is the cinema, let's go duck~"

Wujiaochang, Yida Cinema.

Although it was the premiere in the early morning, there were quite a lot of people because of the superimposed New Year's Eve factor.

The majority of moviegoers are young people, most of whom are students from the surrounding Shanghai University of Finance and Economics or Shanghai University of Finance and Economics.

The name of the movie is "Bump Man vs. Venom". Xu Qiu read the promotional introduction before:

The main story is that these two powerful opponents who are like gods meet in a spectacular war, when the fate of the world is hanging by a thread.

In order to find his real home, Bumpman and his protectors embarked on a difficult journey.

Along with them is a young orphan girl...Maria, who has a unique and powerful bond with Bumpman.

Instead, they find themselves on their forced course with the enraged Venom, causing havoc across the globe.

An invisible force caused a huge conflict between Bumpman and Venom, and the mystery hidden deep in the heart of the earth was also revealed.

Then, Xu Qiu and Han Jiaying watched it in detail, and found that the plot was roughly as follows:

Bumpman meets Venom, they fight, Bumpman loses miserably, but doesn't die...

Next, after going through the plot, they met again and fought again, Bump Man suffered another defeat, but he did not die...

After going back and forth several times, Bumpman and Venom discovered that there is a big BOSS behind the scenes manipulating all this secretly.

As a result, Bumpman and Venom became friends, and they worked together to overthrow the big boss.

In the end, everyone is happy.

As for the plot, it is quite satisfactory, and the special effects of fighting are very good.

The overall score can still be given 7 or 8 points, it is worth watching.

After the movie ended, everyone left in an orderly manner.

Xu Qiu and Han Jiaying held hands on the university road, pressing down on the road.

Passing by an express hotel, Xu Qiu glanced at the school girl, and saw that her walking pace seemed to slow down a lot...

So, Xu Qiu tentatively asked, "Did you bring your ID card?"

Then, I got a low-pitched response from the school girl: "Hmm..."

The two walked into the express hotel, and Xu Qiu took the initiative to say, "Boss, come to a room with a big bed."

"Sorry, there are no rooms available tonight."

"Shall we switch?"

"good……"

"Boss, come to a big bed room."

"Sorry, it's fully booked."

"boss……"

"It's full, it was fully booked a week ago, remember to book early next time."

These are all fast hotels along the road, and none of them have any vacant rooms, let alone double rooms, even the standard rooms are fully booked.

Xu Qiu couldn't help but sigh inwardly, it seems that other people came prepared, as expected, opportunities always favor those who are prepared.

In the end, Xu Qiu and Han Jiaying walked all the way back to school.

Xu Qiu saw the five-star Crowne Plaza Hotel nearby, and said to Han Jiaying, "Try your luck?"

The school girl is not shy now, and said openly: "Okay."

"Hello, is there any room, standard room is also ok?"

"Hello, sir, there are rooms, but now there is only the presidential room, do you want to stay?"

"How much?"

"Hello, sir, the presidential room is 1188 soft sister coins for one night."

"...Come to a room."

...

...

...

(It is said that a few ellipses are several times, crossed out)

Although there is a three-day holiday on New Year's Day, it does not exist in the scientific research circle.

Because the schedule in the research group is to rest on Saturdays and Sundays on January 1 and 2, work as usual on Monday, January 3, and make up shifts on the afternoon of Saturday, January 8, so there is no rest.

Monday morning, January 3.

Xu Qiu has already obtained the two results that were handed over to the simulation laboratory for exploration.

First of all, the device performance of different systems varies with the storage time in the evaporation chamber after the evaporation is completed.

The results show that the device efficiency of the ternary IDIC-M/binary COi8DFIC stack system with the highest efficiency of 16.22% first increases and then decreases as the storage time prolongs.

When the storage time is 12 hours, the device efficiency reaches a peak value of 16.66%.

Xu Qiu's first reaction when he saw the result: "Perhaps, this is the exclusive benefit God left for water paddling experimenters?"

In fact, Xu Qiu did not discover this experimental optimization method of "better placement" before, which was largely influenced by organic synthesis experiments.

Because when doing organic synthesis experiments such as Stille coupling reaction, Xu Qiu found that the faster the reaction, the better the final result, so he directly substituted the same idea when making devices.

This also shows that in doing scientific research, the element of luck is really very large.

In addition, in the experimental phenomenon of "better after placement", other results are also very interesting except that the peak value is reached after 12 hours of placement.

Xu Qiu found that when the storage time reaches 3 hours, the highest efficiency has increased to 16.58%.

After extending the storage time, from 6 hours, to 9 hours, and then to 12 hours, the change in efficiency is not large, about 0.02%, 0.03%, and it is slowly increasing.

After that, if you continue to extend the storage time, the drop in efficiency is also not that big, about 0.02% or 0.03%, which can be considered as the efficiency has stabilized in the short term.

At the same time, the phenomenon of "better placement" is not applicable to all systems.

Xu Qiu studied seventeen standard systems in total, and found that only five of them had the experimental phenomenon of "better after placement", another eight systems were "worse after placement", and four systems were "unchanged after placement". ".

He tried to classify the systems of "better placement", "worse placement" and "same placement", and found that:

The systems of "better after placement" and "worse after placement" are mostly the systems that have not been annealed after the effective layer is spin-coated, and most of the systems that are "unchanged after placement" are systems that have been annealed.

The experimental operation of annealing mainly affects the residual solvent content after the effective layer is spin-coated. If it is not annealed, chlorobenzene with a boiling point of more than 100 degrees Celsius, and the solvent additive DIO with a higher boiling point that can reach more than 200 degrees Celsius will definitely be affected. Some leftovers.

Therefore, Xu Qiu believes that the experimental phenomena of "better placement", "worse placement" and "same placement" can be attributed to:

In the vacuum environment of the evaporation chamber, the effect of volatilization of the residual solvent in the device on the morphology of the effective layer.

For solvents such as chlorobenzene and DIO, they are not easy to volatilize under the conditions of normal temperature and pressure.

Under normal temperature and low pressure conditions, it will gradually "run out" from the active layer of the device and diffuse into the vacuum atmosphere outside.

The process of solvent volatilization takes a certain amount of time.

The normal evaporation process lasts only about 2 hours, which is not enough to completely evaporate the residual solvent inside the effective layer.

Now extend this time for an additional 3 hours or more to allow the solvent to evaporate almost completely.

The process of solvent volatilization will also be accompanied by changes in the microscopic morphology of the effective layer.

If the impact is positive, the result of the reaction is "better placement", otherwise, "worse placement".

In the device after the annealing operation, because there is less solvent remaining in the active layer, it can be considered that there is no solvent volatilization process.

Therefore, the additional rest time has little effect on the device performance after annealing.

There may be changes after long-term placement, but the performance in a short period of time is "unchanged".

Of course, these are Xu Qiu's views. Whether they are correct or not can only be tested through continuous experiments.

However, he feels that there is nothing wrong with this theory, at least the experimental results at this stage support his inferences.

Xu Qiu decided to put the experimental operation of "vacuum placement" together with thermal annealing and solvent annealing as a way to optimize the processing technology.

In terms of specific operation, the evaporation can be completed at night, without opening the evaporation cabin, and the substrate is "stuck all night" in the cabin, and the test can be carried out after coming over in the daytime the next day.

Doing so will take longer.

However, in order to improve the performance of the device, it is also worth paying the cost.

It has little impact on the simulated laboratory, because there are enough evaporation chambers inside, and different evaporation chambers can be recycled for experiments.

On the other hand, the strategy of introducing PCBM into the top battery has also achieved breakthrough progress.

Now the results of the binary IDIC-M/ternary COi8DFIC system in the simulation laboratory show that the device efficiency has reached 16.83%.

Compared with 16.22% of the previous ternary IDIC-M/binary COi8DFIC system, it has increased by 0.61%.

This increase is relatively large at this stage.

However, it is also normal.

In the previous reports of Li Dan’s research group at the National Center for Nanoscale Science and Technology, the improvement between their binary and ternary systems was also about 1%, and it is not surprising that there can be a 0.61% improvement in stacked devices.

Now, the two strategies of "vacuum storage" and "top battery ternaryization" have both achieved breakthroughs in performance, which can be described as double happiness.

Moreover, these two strategies were independent of each other when Xu Qiu was exploring.

In other words, if you combine them together and look at the current trend, it can be said that the sword is 17%!

Although Xu Qiu felt a little dreamy, in just over a month, he increased the efficiency of the stacked device from the original 10% to the current close to 17%.

But in fact, from the semi-empirical analysis results, it is normal that the performance of stacked devices is significantly higher than that of single-junction devices, and it is abnormal that the performance of stacked devices is similar to that of single-junction devices.

For example, as of June 16, 2018, among all photovoltaic systems, the world's highest efficiency records for three-junction and four-junction stacked devices have reached 44.4% and 46.0%, respectively.

The king of single-junction devices, gallium arsenide photovoltaic devices, has a maximum efficiency of only 35.5%, a difference of 10%.

The field of organic photovoltaics has been in an abnormal range before, mainly because no suitable near-infrared acceptor material has been found.

Now Xu Qiu's team is leading the entire field of organic photovoltaics, filling this vacancy, and it is not surprising that they can achieve a "leap" in efficiency.

If it can achieve 17%, it is already very good data.

It seems that the 17% of organic photovoltaics is far from the highest record of 46.0% in other photovoltaics, but as long as the device cost of the former can be one-third or even lower than that of the latter, the actual gap will not be that big.

This is why some fields have poor performance, but researchers have always been keen to study them.

PS: A total of 21W+ words were updated in March, with an average of 7000+ words per day. Continue to work hard in April.

PS2: The current monthly ticket is 1819 votes. I didn’t expect it to increase by more than 300 votes in one day, nearly 400 votes. Now it’s less than 200 votes to break 2,000. Looking forward to getting up tomorrow morning, I can see that the number of monthly tickets starts with 2... …