Chapter 73: Experimental ideas (part one)

　　 The two borrowed a trolley from the guard, put four empty buckets in the car, and then pushed the car to the old chemical building.
　　 There is a special faucet, and the direct flow out is deionized water.
　　 On the way, Xu Qiu asked curiously:
　　 "I have used deionized water for so long, and I still don't know the difference between it and distilled water."
　　 "The main reason is the difference in preparation methods," Chen Wanqing said:
　　"For deionized water, the coarser particles need to be filtered through quartz sand first, then the high pressure pass through the reverse osmosis membrane, and finally UV sterilization to remove microorganisms in the water.
　　 If the resistivity has not reached the requirement of pure water at this time, an ion exchange process can be performed again, and the resistivity can reach more than 18 megaohm cm.
　　 Relatively speaking, distilled water is only vaporized and then condensed, and its resistivity is generally not as high as deionized water. Therefore, most of the high-purity deionized water used in the semiconductor industry is used. "
　　……
　　 The two transported deionized water back to the laboratory.
　　 Since Feifei Wu is still using evaporation equipment, she cannot add water to the water storage tank now.
　　 Xu Qiu copied the deionized water and the repaired circulating water system to the simulation laboratory, checked it again, and found no abnormalities.
　　 "Sister, we should do business," Xu Qiu said:
　　 "Let’s discuss the synthesis of donor materials."
　　 "Yes, I have to report tomorrow." Chen Wanqing said:
　　 "Then you can briefly introduce the history of the development of organic photovoltaic materials. I happen to be able to check your literature reading."
　　 Xu Qiu has insisted on reading literature for one hour a day for more than two months, and he has not stopped even during the summer vacation.
　　 So he was full of confidence:
　　"Organic photovoltaic materials, that is, the effective layer materials used in battery devices, are divided into donors and acceptors.
　　 They were originally called electron donors and electron acceptors. Later, for the convenience of writing and communication, people omitted the word ‘electronic’.
　　 After being exposed to light, the donor material undergoes a photoelectric reaction to generate excitons, that is, electron-hole pairs. The excitons are split into free electrons and holes at the donor/acceptor interface.
　　 Then, free electrons are transferred from the donor to the acceptor, which is equivalent to the donor material giving electrons, which is the origin of the name of the electron donor.
"Under the action of the built-in electric field, electrons are transported to the negative electrode of the electrode via the acceptor material, and holes are transported to the positive electrode of the electrode via the donor material, forming a potential difference between the positive and negative electrodes of the battery.
　　 When the battery is connected with a load, a photocurrent is formed. "
　　 "The principle part is basically correct, go ahead." Chen Wanqing applauded.
　　 "The research progress of acceptor materials is relatively slow." Xu Qiu said:
　　" Fullerene C-60 was first used, and the widely used acceptor material is still fullerene derivative PCBM.
　　The only improvement is that the original C-60 is not soluble in organic solvents, so it needs to be vapor-deposited on 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 perylene diimide derivatives, etc., but the efficiency has not been high, and it is difficult to exceed 10%.
　　 In recent years, donor materials have made great breakthroughs, and there is a lot of room for research.
　　Senior sister, did she choose to be the donor material for this reason? "
　　 "Yes, large research space means that it is easy to post articles," Chen Wanqing admitted generously.
　　 "Go ahead, don't interrupt."
　　 "Polymer donor materials can be divided into three generations as a whole." Xu Qiu said:
　　" was originally a derivative of poly-p-styrene, PPV, and later the classic poly-3-hexylthiophene, P3HT, and now it is a D-A copolymer represented by PTB7-TH.
"Polymer" is a macromolecule composed of one or more structural units repeatedly connected, and the relative molecular mass is usually more than 10,000.
　　PPV and P3HT are all homopolymers. As the name suggests, they are polymers with only one structural unit.
　　The third generation of D-A copolymers is formed by the polymerization of two structural units D unit and A unit.
　　 Because of the various types of D and A units, the amount of materials for the third-generation donor materials has also expanded dramatically. "
　　 "Yes," Chen Wanqing took over the words:
　　"Most of the donor materials have poor photoelectric properties, so they can only be distributed in the 234 districts for irrigation.
　　 Materials with excellent performance, such as PTB7-TH, can also be published in major journals of "Nature", such as "Nature Optics".
　　 But the current efficiency of up to 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 systems based on PCBM receptors.
　　 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 way out in the field of organic photovoltaics is to synthesize a new high-performance receptor to replace and overthrow PCBM's perennial monopoly.
　　Of course, these are the things that will come later, so let's think about what is right now.
　　 Let me talk about my thinking. "
　　" Before, I only learned the synthesis method with Teacher Wei, using relatively cheap raw materials, but I learned all the experimental operations.
　　 But if you synthesize new materials, the experimental conditions will definitely change, so you 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, and make a ternary polymer. For example, I use three structural units D, A1, and A2 for polymerization. "
　　 "Senior sister, wait a minute, why do I hear you so familiar to me?" Xu Qiu thought for a while and said:
　　 "Isn't this the idea of ​​senpai's last article, but this time it changed to use three units to synthesize one donor material."
　　 Chen Wanqing smiled, did not reply positively, but raised a question:
　　 "Boy, do you have synthesis experience?"
　　 "No." Xu Qiu shook his head.
　　 "Do you know how to improve the main chain of polymer molecules to improve its performance?"
"not sure."
　　 "Do you know the influence of branched chains on molecular properties?"
　　 "Crystalline performance?"
　　 "The answer is not comprehensive, but it actually includes solubility, crystallization performance, energy level structure, and even light absorption performance, etc., which will have an impact." Chen Wanqing said:
　　 "However, even if I know the impact, I only know it from other people's literature. After all, this experience is not my own.
　　 Let me design a new molecular structure, just like exploring a new field, which requires courage and ability.
　　 I don't want to spend a lot of time, and as a result I can't do anything. That's why I chose a more reliable experimental idea for the article.
　　 After all, the synthesis is as deep as the sea, the experiment cycle is long, it takes several months at every turn, and in the end, I don’t know what the result will be. I’m afraid I don’t publish enough articles and it’s difficult to graduate.
　　 But the younger brother has plenty of time and can choose to challenge.
How about 　　, do you have any ideas? "
　　 "Yes." Xu Qiu said.
　　 "It's really there, let's hear it."