I Have a Research Support System

What should I do?

Facing the junior girl's eyes asking for help, Xu Qiu thought for a moment and said:

Well, I'll watch you complete a batch of devices, find out what's wrong, and give you some suggestions.

Okay, that's great. Han Jiaying said happily.

...

After Wu Feifei finished the experiment, the junior girl took over the spin-coating glove box.

The first step to start is solution preparation.

She has three kinds of materials, so she prepared three sets of chlorobenzene solvent solutions.

From the perspective of solvent selection, there is no problem.

After all, she does not have a simulation laboratory, and it is a good choice to use the previous experimental conditions when trying the preliminary experiment.

However, she changed the concentration of the solution. The concentration of P2T and P3T is 8 mg per milliliter, while that of P5T is 6 mg per milliliter.

For Xu Qiu's P4T system, the optimal concentration is 8 mg per milliliter.

In this regard, Han Jiaying took the initiative to explain:

Initially, I used 8 mg per ml for all three solutions.

But I found that the P5T solution at this concentration, even if the solution temperature is heated to 90 degrees Celsius, still cannot be dissolved well, and some solid substances will remain on the bottle wall.

I added some more solvent and diluted it to 6mg/ml before it could be used normally.

For the two systems of P2T and P3T, they can be dissolved normally.

It's the solubility problem again. Xu Qiu said with emotion.

Again? Han Jiaying asked suspiciously.

Well, when I was doing experiments before, I encountered solubility problems twice, Xu Qiu explained:

However, I solved it all later. At that time, you hadn't come to Teacher Wei's research group yet.

So that's the case, how did the senior brother solve it?

The first time was Soxhlet extraction with chloroform to treat the crude polymer product and remove the insoluble matter in the product, Xu Qiu said:

The second is the modification of the molecular structure, which fundamentally improves the solubility of the polymer material by increasing the length of the side chain.

In fact, I almost guessed the reason for the solubility problem you encountered this time.

Really, so powerful? Han Jiaying said.

After all, the three systems you made are similar to my P4T system, and the relevant experimental experience can also be used and analogized. Xu Qiu said:

The optimal OD side chain used on P4T molecules may not necessarily be used in P2T, P3T, and P5T molecules, but it is also optimal.

I guess, because the conjugated length of the main chain is increased in the P5T molecule, the relative proportion of the side chain will decrease.

It is manifested in the solubility, that is, the solubility is reduced. If you want to improve its solubility, you need to extend the length of its side chain.

For the two molecules, P2T and P3T, slightly shorter side chains can also meet the needs of dissolution, and perhaps shortening the length of their side chains can improve performance.

It sounds reasonable, Han Jiaying said:

Brother, let's guess again, what are the efficiencies of these three systems?

You are... a bit too embarrassing, Xu Qiu said, not knowing whether to laugh or cry:

If I know the efficiency by just looking at the molecular structure, then I don't need to do experiments.

Seeing Han Jiaying's serious face, Xu Qiu cooperated and said:

Let me make a rough guess. P3T is the highest, and I can't judge the other two.

Hey, you really guessed it right, Han Jiaying said:

It is true that P3T is the highest with 4%, followed by P5T with 3%, and the efficiency of P2T is very low, less than 1%.

Well, with the result, the cause can still be roughly deduced. Xu Qiu thought for a while and said:

Everything assumes that there is no major problem with your experimental operation.

The poor performance of P2T may be due to the fact that the D unit is too small, and a long side chain is connected to it, which hinders its contact with PCBM, thereby reducing the donor/acceptor interface, resulting in poor exciton splitting efficiency.

If similar results are still obtained in subsequent experiments, research in this direction can be temporarily abandoned.

As for P3T and P5T, as I analyzed before, the length of their side chains can be reduced and increased by one unit, and the performance may be improved.

I didn't expect that senior brother would be able to analyze so many things just from the experimental conclusion of efficiency. Han Jiaying said:

Hey, I was at a loss when I got the results of the experiment before, and I didn't know what to do next. Now everything is clear.

These are all conjectures from the molecular structure level. I'm just pointing out the direction of improvement for you in the future, and it may not be right. Xu Qiu said:

How to do it depends on you. Of course, if you have any questions, you can still come to me at any time.

Yeah, Han Jiaying nodded and said, Then I will continue the experiment.

Prepare zinc oxide solution, clean the substrate, and spin-coat zinc oxide.

Han Jiaying has mastered these basic experimental operations pretty well, and there are no obvious problems.

The experiment was only started this afternoon, and there was not enough time to prepare and test a batch of devices.

Therefore, the two made an appointment to continue the spin coating, evaporation and testing of the effective layer on Friday afternoon.

...

Time flies.

At 1:20 p.m. on Friday, Xu Qiu and Han Jiaying entered the laboratory on time and occupied the spin-coating glove box.

You can still hear Wu Feifei's voice from behind:

I don't make devices today, no one will grab the glove box from you, so you are in a hurry.

Xu Qiu ignored her, turned to the school girl and said:

I feel like Wu Feifei is envious of me, the new junior Cheng Mingbo, I basically can't see other people.

You are still reliable. Fortunately, I chose you in the first place.

Han Jiaying didn't know how to answer the conversation for a while, and after thinking for a while, she whispered:

I'm lucky too.

What are you mumbling about?

No, it's nothing, I'm going to start spinning.

After speaking, she began to heat the solution and the substrate, but the experimental operation was a little flustered.

Fortunately, it didn't take long before her movements gradually stabilized.

First piece, start spin coating.

Xu Qiu watched from the side, her technique was still a bit unfamiliar.

He didn't point it out immediately, but continued to observe.

After the spin coating was completed, Han Jiaying picked up the substrate with tweezers.

Observed by the two together, there is a circular pattern in the center of the film, which is caused by the true hot spin coating operation method, and there is no problem with this.

However, the obtained film was not very smooth, and there were several small bumps on it, which may be undissolved polymer or polymer precipitated during film formation.

Xu Qiu suddenly thought that he didn't seem to have taught his junior this operation in a serious way, because this operation was very difficult, and he had done it himself before, with his junior watching.

However, this method can only rely on continuous trial and improvement of proficiency, and there is no shortcut.

The method of true thermal spin coating is not skilled enough, which should be the reason for the low efficiency of your device, Xu Qiu commented:

Let's practice with a glass slide until a uniform film can be obtained stably.

Okay. Han Jiaying said.

After speaking, she began to practice true thermal spin coating with glass slides, while Xu Qiu gave instructions outside.

This scene is a bit familiar, as it was when I taught Chen Wanqing the spraying method.

The difference is that Han Jiaying's talent is higher.

Thanks to Yi Jiaxuan'er for tipping 5,000 starting coins, Dajiang Dahe 1111, and Ziwang Fuyun for tipping 100 starting coins.