I Have a Research Support System

It turned out that when Xu Qiu was spin-coating the perovskite film, his attention was focused on how to remove the white fog that appeared and obtain a uniform and smooth film, while ignoring the difference between the preparation of the transmission layer and the effective layer.

The thickness of the perovskite effective layer film is usually more than 200 nanometers, while the thickness of the general transmission layer material is preferably between 5-50 nanometers.

The early organic solar cells did not have a transport layer. Later, researchers found that the introduction of the transport layer was helpful for charge transport and improved the photoelectric performance of the device. Only then did the researchers start to use the transport layer.

However, when the thickness of the transport layer is too high, it will also increase the possibility of charge recombination, resulting in a decrease in device efficiency.

This also explains why the performance of the device without the transport layer is higher than that of the perovskite transport layer, and the performance of the latter increases with the increase of the rotational speed.

All because Xu Qiu applied the perovskite film too thickly.

…………

Back in the dormitory, Xu Qiu and Tao Yan greeted each other, then lay on the bed and entered the simulation laboratory.

The solution in the simulation laboratory is still in the same state as when he left last time, so there is no need to worry about the deterioration of the solution.

In the daytime experiment, the 4# sample has the highest efficiency, so it may be the most suitable material for the transmission layer among the four perovskite materials.

Xu Qiu simply prepared 5 ml of 10% mass fraction of 4# sample solution directly as the mother solution.

It can then be directly diluted to obtain solutions of other concentrations.

Unlike organic polymer materials, perovskite materials are small molecules that dissolve faster and obtain more accurate concentrations, so it is easy to adjust the concentration.

During the solution preparation process, he was also exploring the 0.5-2x speed function of the simulation laboratory.

He found that after turning on the double speed function, except for the consciousness and his 'body', all other experimental instruments can be in the double speed state.

When performing delicate operations such as weighing medicines, he can adjust the time rate to 0.5 times to improve the accuracy of the operation.

When waiting for ultrasonic cleaning, etc., the time rate can be adjusted to 2 times to speed up the experiment process.

The points consumed are calculated according to real time. When 2x speed is turned on, 200 points will be consumed per real hour.

In addition, he can also delineate the change of time flow rate in a designated space.

For example, he was able to put the ultrasonic cleaner at 2x speed and the glove box at 0.5x speed.

As for the points consumed, the maximum double speed in the entire space is taken, that is to say, as long as an instrument is turned on at double speed, it will be consumed according to the points of double speed.

After some experience, Xu Qiu was very satisfied with this function.

Next, he's ready to experiment.

In order to improve the experimental efficiency, Xu Qiu plans to only make devices with 4# sample as the transport layer material.

He did not plan to make PEDOT standard samples and samples without transmission layer, which is why he is confident in his own operation.

First, prepare the solution.

During the day, the concentration of 10% mass fraction is used, and the rotation speed is 2000-4000r.p.m., and the obtained film thickness is obviously too high.

Xu Qiu adjusted its concentration to 1%, 2%, 3%, 4% and 5% mass fraction.

Then there's the revs.

Xu Qiu uniformly set it at 5000r.p.m.

This is basically the upper limit of the safe speed of the homogenizer, and if the speed is increased, the substrate may fly out during the high-speed rotation.

In general, to obtain a film with the same thickness, the quality obtained under the condition of high concentration and high rotation speed is better, because the concentration is easier to adjust, so there is no need to change the rotation speed.

The last is to control the interval time of anti-solvent dripping.

The rough test result of the daytime experiment is that there will be no white fog at 5-second intervals.

Xu Qiu additionally set four levels of 4 seconds, 4.5 seconds, 5.5 seconds and 6 seconds.

In this way, there are 5*5=25 conditions in total.

After confirming the experimental conditions, Xu Qiu activated the 2-fold acceleration to dissolve the solution quickly.

…………

Spin-coated perovskite transport layer, organic active layer.

Evaporated calcium and aluminum electrodes.

Ready to test.

When Xu Qiu is testing, the first piece is usually tested with a standard sample, or the sample that he thinks is the most promising.

The purpose of measuring the standard sample is to judge the overall performance of this batch of devices. If the standard sample is lower than the average value, then the performance of the entire batch of devices may also be lower than the average value.

However, he didn’t make a standard sample for this batch, and he didn’t know which condition was better. It was a completely unknown exploration, so he took a random sample, “1%, 5s”.

After testing, the obtained efficiency is 8.66%.

Seeing this result, Xu Qiu breathed a sigh of relief.

This shows that my deduction is correct, and it was indeed too thick before.

Perovskite materials can be used as transport layers, at least better than no transport layer.

However, the efficiency has not reached 10%, maybe the film at this concentration is too thin.

He chose the "2%, 5s" sample and continued testing.

Sure enough, the efficiency has increased, reaching 9.37%.

...

The remaining 23 samples were tested.

Ultimately, the "3%, 5.5s" sample performed best.

The efficiency can reach 10.24%, which is comparable to the efficiency of the PEDOT reference device.

After leaving the simulation laboratory, Xu Qiu checked the time, it was almost twelve o'clock.

I forgot to take a shower in the public bathroom again today, so I had to go to the corridor to take a shower again.

The icy water jet hit her body, Xu Qiu not only didn't feel cold, but also felt very excited.

He was thinking about tomorrow's experimental plan in his mind:

The control range can be further broadened, for example, the solution concentration is 2.5%, 3%, 3.5%, and the speed remains unchanged.

In addition, the other three solution systems can also be done. Although the probability of surpassing the 4# sample is not high, there may be a miracle.

…………

The next day, Xu Qiu went to the laboratory and was surprised to find that there was no one in the laboratory.

After swiping his card to open the access control, he checked his phone, only to realize that today is Saturday and the research team does not go to work.

However, since it's all here, let's do the experiment.

And, good Saturday, no one is fighting him for the glove box.

He started the experiment according to yesterday's idea, and ordered takeaway at the desk outside at noon.

There were no unexpected results.

The performance of 1, 2, 3# samples is not as good as 4#.

Among them, the 2# sample is not bad, and the highest efficiency is 9.6%, but it does not break 10%, after all, it is almost meaningless.

The standard sample efficiency of this batch is 10.10%, while the highest efficiency in the 4# sample reaches 10.46%, the conditions are 2.5% concentration, 5000r.p.m. rotation speed, 5.5 second interval time.

In fact, if the preparation conditions of the standard device are finely regulated as in the experimental group, the efficiency may be higher, but it is not necessary.

This is also an unspoken rule in the industry. When the performance of the two is equivalent, making the experimental group slightly higher than the control group, even if it is not much higher, only 0.3%, will look much more comfortable.

Just as the performance test was coming to an end, Xu Qiu heard someone coming from outside.

It didn't seem to be Teacher Wei's footsteps, so who could it be?

Thanks to ghift for the 200 point reward.