I Have a Research Support System

After the vacuum in the evaporation cabin reached the standard, Xu Qiu and Mo Wenlin returned to the laboratory, and first evaporated molybdenum trioxide with the beam source furnace heating method according to the normal method.

After that, wait for the temperature of the beam source furnace to drop below 100 degrees Celsius, and start preparing for the evaporation of metal electrodes.

Usually, when evaporating thick-film metal electrodes, the evaporation rate is not very important. Sometimes, in a hurry, the electrodes are prepared directly by flash evaporation.

The so-called flash evaporation, which highlights the word flash, is to directly use a large current to fully increase the evaporation rate without blowing the fuse, and the film is coated with a swish.

For comparison, the normal evaporation rate of metal electrodes is about 1 angstrom per second, that is, the evaporation rate of 0.1 nanometer per second, and it takes about 17 minutes to evaporate 100 nanometers.

The speed of flash evaporation may reach 6 angstroms per second, or even more than 10 angstroms per second, and it can be done in a few minutes.

In addition to fast steaming, flash steaming has another advantage, that is, thick steaming and high utilization of the target.

Especially when evaporating gold, because gold is more expensive, in order to prevent waste, it is best to add as little gold target material as possible, and then flash directly.

According to Xu Qiu’s experience, if all the gold is evaporated by flash evaporation and the thickness of the obtained gold film is 100 nanometers, the thickness obtained by evaporation at a normal rate may only be 30-50 nanometers, and the gap is still very large.

Everything has advantages and disadvantages, and flash evaporation also has disadvantages, that is, it will make the film obtained by evaporation uneven.

To give a less vivid example, imagine the process of evaporation as the process of hail, and imagine the surface of the device as a dirt floor. The faster the evaporation rate, the larger the hail particles, and the faster the falling speed, the easier it is for the ground to Smash it out of the hole.

Corresponding to the embodiment of the evaporation process, the faster the evaporation rate, the more the target molecules tend to penetrate into the effective layer or transport layer film, thus forming metal electrodes with different thicknesses at different positions.

When the total thickness of the metal electrode is relatively thick, the influence of uneven thickness is not great. Assuming that the film thickness is 100 nanometers and the thickness deviation is 10 nanometers, the final thickness distribution will also be 100±10 nanometers, which will naturally not affect to the conductivity of the electrode.

But if the thickness is relatively thin, this effect is obvious. The thickness is 10±10 nanometers, and some places are directly disconnected.

Therefore, in order to ensure the continuity of the electrode, the double-layer thin-layer electrodes of 1 nanometer gold and 9 nanometer silver are not only unable to be flashed, but also have to further reduce the evaporation rate.

The evaporation rate Xu Qiu plans to use is about 0.2 angstroms per second, which is equivalent to the rate of evaporation of the molybdenum trioxide transport layer. In this way, it takes about 1 minute to evaporate 1 nanometer of gold, and about 7 and a half minutes to evaporate 9 nanometers of silver. , which is shorter than the usual evaporation time.

The theory is sound, the practice begins.

Xu Qiu set up the parameters of the gold target, including density, Z factor, etc., then started the current heating device, adjusted the current output end to the circuit of the gold target, and at the same time instructed Mo Wenlin:

Mo Wenlin, please record the experimental conditions. Just now the molybdenum trioxide is 565 degrees Celsius, 0.2-0.3 angstroms per second, and the film thickness is 10 nanometers. The next gold and silver electrodes are 1 nanometer and 9 nanometers respectively. The evaporation rate is 0.2 angstroms per second...

Okay. Mo Wenlin nodded, then took out an experiment notebook from the top of the evaporation glove box, and started recording.

The use of such a large-scale instrument needs to be recorded. If there is a problem, it is easier to be held accountable. Of course, it is not entirely for the purpose of holding accountable. This will also prevent the experimenters from forgetting the previous experimental conditions.

Especially for newcomers who are not skilled, if they forget the experimental conditions and there is no old man nearby to ask for advice, they can go through the conditions recorded before and imitate.

Xu Qiu turned the knob and slowly increased the current intensity, from 0 amps to 5 amps, then to 10 amps, and then to 15 amps.

During this process, the real-time evaporation rate displayed by the film thickness meter fluctuates back and forth between ±0.01 angstroms per second, and the fluctuation range is not large.

This is mainly because the density of gold is relatively high. When the film thickness meter converts the evaporation rate through the electrical signal on the crystal oscillator, the density is on the denominator, so the error caused by air flow disturbance will be smaller.

At 15 amps, Xu Qiu stabilized the current and stayed there for a few minutes.

This step is a matter of habit, the purpose is to preheat and raise the temperature of the tungsten wire and the target first.

This step is very useful when evaporating aluminum. On the one hand, it can prevent the evaporation rate from being uncontrolled; The wire was directly fused, resulting in the failure of the experiment.

Although tungsten baskets are used instead of spiral tungsten wires when evaporating gold and silver, there is no harm in being careful.

Xu Qiu continued to increase the current until it reached 17.5 amperes, and the evaporation rate jumped from ±0.01 Angstroms per second to 0.01 and 0.01. At the same time, the current value also began to fluctuate, indicating that the gold target had begun to melt.

After waiting for a few seconds, the evaporation rate reached around 0.10 Angstroms per second and gradually stabilized.

Without hesitation, Xu Qiu directly pressed the reset button of the film thickness meter and the button of the sample shutter at the same time to start the evaporation.

Then, he operates the current control knob with one hand, and puts the other hand on the sample baffle. His eyes are always on the evaporation rate and film thickness, and he plans to stop at any time. After all, it is only 10 angstroms to evaporate 1 nanometer of gold. .

Xu Qiu, don't you need to continue to increase the evaporation rate? Didn't you just say that you should adjust the rate to 0.2 Angstroms per second? Mo Wenlin asked curiously. She has been in the research group for more than a month, but she has never evaporated before. Gold electrodes, the electrode materials that are usually contacted are either aluminum or silver.

This is because the device structure of the molybdenum trioxide transport layer in the field of organic photovoltaics, the three electrodes of gold, silver, and aluminum have little effect on the performance of the device, so cheap silver or aluminum is generally used.

For the perovskite system, if the Spiro transport layer is used, it usually needs to be matched with a gold electrode. The gold target purchased in the group is mainly used for the perovskite system.

The ideal is to achieve a rate of 0.2 angstroms per second before evaporation, but in the specific experimental process, it is necessary to be flexible. Now the condition of 0.10 angstroms per second has been stabilized. If we forcefully pursue the expected conditions of 0.2 angstroms per second , if one is not well controlled, it may directly become a flash. Xu Qiu explained:

There is no turning back for gold evaporation, because the material is limited. Once the rate goes up, it is impossible to wait for the rate to drop, because the gold target may have been consumed by then, so we can only finish steaming.

I see. Mo Wenlin nodded.

Xu Qiu constantly adjusted the current to keep the evaporation rate at 0.1-0.2 Angstroms per second.

After more than a minute, the value displayed by the film thickness meter finally jumped from 9 angstroms to 10 angstroms. Xu Qiu immediately closed the sample shutter, and then slowly reduced the evaporation current until the value dropped to 0.

After the gold film was evaporated, Xu Qiu finally felt relieved. He wasn't worried about not having enough gold, because he had already experimented in the simulated laboratory before, mainly because he was afraid of accidents such as uncontrolled evaporation rate.

Then, Xu Qiu adjusted the current output terminal to the circuit of the silver target, and set it as the parameter of silver in the film thickness meter.

The difficulty of evaporating silver electrodes is relatively small, because the amount of added target material is sufficient, and there is no need to worry about the problem of high evaporation rate. At worst, just drop the current back and raise the temperature again.

There was no accident in this step. Xu Qiu successfully vapor-deposited the silver electrode at a rate of 0.1-0.2 angstroms per second, then tilted his head and asked, Mo Wenlin, have you lost your studies?

Learning is useless, study is useless. Mo Wenlin thought for a moment, and responded: The current should be increased slowly, and the evaporation rate should be stable at 0.1-0.2 angstroms per second. Plating is complete.

Well, the summary is not bad. Xu Qiu nodded, and then raised his finger to the evaporation cabin.

Mo Wenlin understood, walked to the side of the glove box evaporation cabin, twisted the nitrogen valve and started to deflate.

More than half a minute later, the vapor deposition hatch made a duang sound, and the hatch opened.

After closing the nitrogen valve, Mo Wenlin entered the glove box, took out the eight vapor-deposited devices, and placed them in a petri dish.

Then, she took a piece of 1# device with tweezers, picked it up and observed it for a while, and said:

It is indeed a translucent device, through which you can see what is behind it. It is just such a thin layer of electrodes, can it really conduct electricity?

You'll know if you try it. By the way, remember to test two sets of data, one set is for front lighting, and the other is for back lighting. Xu Qiu is confident, and he thinks that the evaporation control is still very perfect. , as long as there is no problem in the spin coating process before Mo Wenlin, it is basically relatively stable.

Okay. Mo Wenlin nodded and started the test.

1# system is PCE10:IEICO-4F system.

The highest front lighting efficiency is 9.03%, and the highest rear lighting efficiency is 5.24%. This result is basically consistent with the results obtained by Xu Qiu in the simulation laboratory before.

9% efficiency is not bad. Mo Wenlin said with a smile, and then began to think: How to optimize...

After a while, Mo Wenlin suddenly thought of something, turned her head and asked, Xu Qiu, should we prepare devices with different electrode thicknesses...

Bingdog~ Xu Qiu nodded: I plan to prepare translucent devices with a thickness of 10, 12, 14, 16, 18, and 20 nanometers.

Mo Wenlin was stunned for a moment, and said pitifully: That's not to say that at least 30 batches of devices should be made...

Including 100nm opaque devices, more than 35 batches will be made. Xu Qiu said in an old-fashioned way: It's time to dedicate yourself to science. Comrade, I am optimistic about you.

Mo Wenlin still looked pitiful and looked at Xu Qiu with wide eyes.

Xu Qiu couldn't stand it anymore: I'll go to Teacher Wei to fight for you.

Mo Wenlin immediately changed her appearance, and said cheerfully: OK, it's a deal, and I promise to dedicate myself.

Xu Qiu shook his head, sure enough, the girls' acting skills are all MAX.

But it doesn't matter if he gives up a co-one, anyway, the family is big and the business is great, this article is not bad, even if it is a co-one, he is also on it, and the system will recognize it when he posts an article in the first district.

Moreover, Xu Qiu can also understand Mo Wenlin, coming here as a joint trainer, the external environment is very unfriendly to her, and it is very difficult to read articles, so naturally she can read one article at a time.

PS: Happy New Years Eve everyone~