I Have a Research Support System

In the first week of the exam month, Xu Qiu's daily schedule was carried out in an orderly manner according to the plan.

mock lab.

Continuing with last week's experiment.

The problem encountered before was whether the active layer solution should be applied hot or cold.

After Xu Qiu thought about it for dozens of seconds, he slapped his forehead and made a decision:

Since you don't know which condition is better, just try them all.

Experimental results will give the answer.

He has studied Polymer Chemistry before and knows that there are many differences between high polymers and small molecules.

For polymer materials, it is not a pure substance, but a mixture of polymers with different molecular weights.

Therefore, it is difficult for researchers to accurately measure the components, and they can only calculate its average molecular weight by experimental means.

The molecular weight and molecular weight distribution of polymer materials are usually characterized by number average molecular weight, weight average molecular weight and polydispersity coefficient.

Therefore, for polymer materials prepared in different batches, their molecular weight and polydispersity coefficient are different, so the properties will naturally be different, and even the same batch of materials will have subtle differences from each other.

Therefore, when it comes to polymer materials, the experimental conditions obtained through exploration are generally only valid for the same batch. If the batch is changed, the optimal experimental conditions will change.

Fortunately, the senior sister bought 500 mg of PTB7-TH at one time, which is enough for several months, so it is necessary to spend some effort to find out the best conditions.

Combined with the experimental conditions of other researchers in the literature, Xu Qiu designed his own experimental plan.

He first added 833 ml of chlorobenzene solvent to the 25#15# solution after the last dilution with a pipette gun, diluted it to 10 mg per ml, relabeled it as 25#10#, and then placed it in a 90-degree Celsius heating Mixing table.

Then the 10# solution was taken off from the heating and stirring table, and placed on the bottle rack to wait for its natural cooling.

The other 15# and 20# solutions are not operated and are still placed on the heating and stirring table.

A total of four sets of solutions were obtained, of which 10# was used for cold coating, 15#, 20#, 25# and 10# were used for hot coating.

For 12 substrates, each set of solutions adopts 3 rotation speeds, which are tentatively set at 1500, 2000, and 2500 r.p.m.

To reduce experimental variables, he decided not to add solvent additives and not to perform an annealing operation.

Then spin coating, evaporation and testing are carried out.

Finally, the highest efficiency of this batch of devices was produced in the 20#, 2500 sample, which was 8.22%.

The efficiency values ​​of all other samples are also above 7%.

After completing the experiment, Xu Qiu recorded the experimental results in the experiment record book, and then analyzed:

First, under the current experimental conditions, the higher the solution concentration, the better the photoelectric performance.

Secondly, under the current experimental conditions, the cold coating method and the hot coating method have little effect on the device performance.

In the end, a total of 12 experimental conditions were used, but the fluctuation of the photoelectric performance of the device was small, which shows that the material performance of PTB7-TH is indeed excellent, and the dependence on the experimental conditions is low. This point is compared with P3HT. He heard from his senior sister that when she first made P3HT, she completely referred to the experimental conditions in the literature, but the device efficiency was only less than 1%.

Xu Qiu is quite satisfied with the data of the best efficiency of 8.22%, after all, this is the first attempt.

Although the results reported by other researchers' articles are generally above 10%, and even the highest is 12.2%, but that is the best performance they obtained after continuous exploration and repeated improvement of experimental conditions.

After that, Xu Qiu changed the speed based on the last result and made another batch of devices.

He prepared samples of 20# solution at 2500, 3000, 3500r.p.m.

The highest efficiency occurs in the 20#, 3000 sample, which is 8.40%.

…………

On Sunday, Xu Qiu received a message from her senior, saying that the PEN substrate had been delivered to the laboratory.

Xu Qiu went to the laboratory.

Hey, Xu Qiu, why are you here? Chen Wanqing said.

Sister, didn't you say that the PEN substrate has arrived, so I'll come over and have a look. Xu Qiu said.

I just want to let you know that you don't do the experiment now, so you don't have to review it properly. Chen Wanqing said so, but she still got up and entered the laboratory, and took out the PEN substrate.

Xu Qiu took the substrate and examined it carefully.

The substrate is a large roll that is rolled up. It has a hard texture when bent. Its surface is transparent with a little light yellow. It is coated with ITO on one side, and the side with ITO is covered with a layer of peelable film. Plastic protective film.

Xu Qiu calls the system:

System, can only copy the PEN substrate without changing other items in the simulation laboratory?

【Can. 】

Then copy it.

[Copy successfully. 】

Xu Qiu suddenly thought, wouldn't it be possible to bring other things to the simulation laboratory.

But if you think about it carefully, it seems useless, even if you can bring it in, you can't take it out, it's just virtual.

He put the PEN substrate back in his hand and asked:

Sister, did the experiment go well recently?

I'm going to make a PTB7-TH device recently, but it doesn't seem to dissolve very well. Chen Wanqing frowned.

Well, what are the experimental conditions?

Well... the chloroform solvent I used has a total concentration of 10 mg per milliliter, giving the receptor mass ratio of 1:1, that is, adding 5 mg of PTB7-TH.

But after stirring for several days, the solution is still not good, and there will always be solid residues on the bottle wall.

But I dare not adjust the concentration of the polymer too low, for fear that the film-forming property of the solution is not good.

I didn’t have this kind of problem when I was doing P3HT before, hey. Chen Wanqing said.

Xu Qiu thought to himself: Senior sister's progress is a bit slow, if it continues like this, after a month, even if I figure out the optimal conditions, I won't dare to use them directly.

Why don't I give the senior a hint, guide the senior step by step, and let her try out a similar condition first, and finally I will come up with the optimal condition, so it won't look so obtrusive.

Thinking of this, he said:

Maybe you can try heating the solution. I am reviewing Polymer Chemistry recently, and I saw a time-temperature equivalence principle in it. I think it can be extended to the problem of solution dissolution. I think increasing the temperature should speed up the polymer. dissolve.

But this is chloroform solvent, oh— Chen Wanqing said: You mean to change the solvent, use chlorobenzene or dichlorobenzene, will it cost too much raw materials?

If you don't want to let your child be a wolf, Xu Qiu said, And if you use the spraying method, you only use 20 microliters at a time, and one milliliter of the solution can be used more than 40 times. Even if you use 10 mg of PTB7-TH, it is only 140 yuan. On average, the cost of the solution to make a substrate is only more than three yuan.

Your math is really good, Chen Wanqing said, It sounds reasonable, okay, let me give it a try.

Xu Qiu was not too worried about the senior sister's experimental operation ability, and added:

The heating temperature can be slightly higher, such as 75 degrees, 90 degrees, etc. The polymer and PCBM are relatively stable in a nitrogen atmosphere.

Okay, okay. Chen Wanqing nodded and recorded it.

Now, it should be fine.