I Have a Research Support System

The two went to the doorman to borrow a trolley, put four empty buckets in the cart, and then pushed the cart to the old chemical building.

There is a special faucet here, and the water that flows out is directly deionized water.

On the way, Xu Qiu curiously asked:

"I've been using deionized water for so long that I don't know the difference between it and distilled water."

"The main reason is the difference in the preparation method," Chen Wanqing said:

"In the case of deionized water, it is first necessary to filter coarse particles of impurities through quartz sand, then pass it through a reverse osmosis membrane under high pressure, and finally undergo ultraviolet sterilization to remove microorganisms in the water.

If the resistivity has not reached the requirement of pure water at this time, the ion exchange process can be carried out again, and the resistivity can reach more than 18 megohm cm.

Relatively speaking, distilled water is only vaporized and then condensed, and its resistivity is generally not as high as that of deionized water. Therefore, most of the semiconductor industry uses high-purity deionized water. "

...

The pair transported deionized water back to the lab.

Since Wu Feifei is still using the evaporation equipment, water cannot be added to the water storage tank now.

Xu Qiu copied the deionized water and the repaired circulating water system into the simulated laboratory, checked it again, and found no abnormalities.

"Sister, it's time for us to get down to business," Xu Qiu said:

"Let's discuss the synthesis of donor materials."

"That's right, there is still a report tomorrow." Chen Wanqing said:

"Then first, let's briefly introduce the development history of organic photovoltaic materials. I can just check your literature reading."

Xu Qiu has insisted on reading literature for an hour every day for more than two months, even during the summer vacation.

So he said with confidence:

"Organic photovoltaic materials, that is, the active layer materials used in battery devices, are divided into two types: donors and acceptors.

They were originally called electron donors and electron acceptors. Later, people omitted the word "electronic" for the convenience of writing and communication.

After being illuminated, the donor material undergoes a photoelectric reaction to generate excitons, that is, electron-hole pairs, and the excitons are split into free electrons and holes at the interface of the donor/acceptor.

Then, the free electrons are transferred from the donor to the acceptor, which is equivalent to the donation of electrons by the donor material, which is also the origin of the name electron donor.

Under the action of the built-in electric field, electrons are transported to the negative electrode of the electrode through the acceptor material, and holes are transported to the positive electrode of the electrode through the donor material, and a potential difference is formed between the positive and negative electrodes of the battery.

When the battery is connected with an external load, a photocurrent is formed. "

"The principle part is basically correct, let's continue." Chen Wanqing praised.

"Research on receptor materials is progressing relatively slowly." Xu Qiu said:

"Fullerene C-60 was first used, and up to now, the widely used acceptor material is still PCBM, a derivative of fullerene.

The only improvement is that the original C-60 cannot be dissolved in organic solvents, so it needs to be evaporated onto the device, while PCBM can be blended with the donor material and spin-coated together.

Of course, researchers have also developed other acceptor materials, such as derivatives of perylene diimide, etc., but the efficiency has not been high, and it is difficult to break through 10%.

In recent years, great breakthroughs have been made in donor materials, and there is a lot of room for research.

Is it because of this reason that senior sister chose to make the donor material? "

"That's right, a large research space means that it is easy to publish articles," Chen Wanqing admitted generously.

"Go on, don't interrupt."

"Polymer donor materials can be divided into three generations as a whole." Xu Qiu said:

"At first it was polyparastyrene, a derivative of PPV, later it was the classic poly-3-hexylthiophene, P3HT, and now it is a D-A copolymer represented by PTB7-TH.

A polymer is a macromolecule that is repeatedly connected by one or more structural units, and its relative molecular mass is usually above 10,000.

PPV and P3HT are both homopolymers, as the name suggests, are polymers with only one structural unit.

The third-generation D-A copolymer is formed by the polymerization of two structural units, D unit and A unit.

Because of the wide variety of D and A units, the number of third-generation donor materials has also expanded rapidly. "

"Yes," Chen Wanqing took over the conversation:

"Most of the photoelectric properties of the donor materials are not very good, so they can only be published in journals in the second, third and fourth districts.

Materials with excellent performance such as PTB7-TH can also be published in major sub-journals of "Nature", such as "Nature Optics".

However, the current maximum efficiency of about 12% is still not enough. It is basically impossible to reach the top of the main journal of "Nature".

I think the main reason is that these are PCBM receptor based systems.

And this system has a big problem, that is, PCBM hardly absorbs visible light, so the transmission loss of sunlight is very large.

I think the future of the organic photovoltaic field lies in the synthesis of a new high-performance acceptor to replace and overthrow PCBM's perennial monopoly.

Of course, these are things for the future, let's consider the present first.

Let me talk about my thoughts. "

"Before, I only learned the synthesis method from Mr. Wei, and I used relatively cheap raw materials, but I learned all the experimental operations.

However, if new materials are synthesized, the experimental conditions will definitely change, and we still have to explore again.

So I plan to find two high-performance D-A polymers that have been reported.

Blend them at the molecular level to make a ternary polymer. For example, I use three structural units D, A1, and A2 for polymerization. "

"Senior sister, wait a minute, why does your idea sound so familiar to me?" Xu Qiu thought for a while and said:

"Isn't this the idea of ​​my sister's last article, but this time I changed it to use three units to synthesize a donor material."

Chen Wanqing smiled, and instead of answering directly, she asked a question:

"Student, do you have experience in synthesis?"

"No." Xu Qiu shook his head.

"Do you know how to improve the main chain of the polymer molecule to improve its performance?"

"not sure."

"Do you know how branching affects molecular properties?"

"Crystal performance?"

"The answer is not comprehensive. In fact, it includes solubility, crystallization properties, energy level structure, and even light absorption properties, etc., which will all have an impact." Chen Wanqing said:

"However, even if I know what the impact will be, I only know it from other people's literature, and this kind of experience is not my own after all.

Asking me to design a new molecular structure is like exploring a new field, which requires courage and ability.

I don't want to spend a lot of time and end up with nothing to do, so I chose a more secure and easy-to-publish experimental idea.

After all, it is as deep as the sea once you enter the synthesis, and the experiment period is long, often several months, and if you don’t do it, you don’t know the result at the end. I am afraid that I will not publish enough articles, and it will be difficult to graduate.

But the junior has plenty of time, so he can choose to challenge it.

How about it, any ideas. "

"Yes." Xu Qiu said.

"It really is, let's hear it."