Chapter 99: Solubility problem again

　　 The processing is completed, it is almost eleven o'clock.
　　 Xu Qiu returned to A501 and sat on the sofa thinking.
　　Zhangjiang also has a bathroom here, but there is no change of clothes or toiletries.
　　 There is no way, I can only leave it overnight.
　　 After a brief wash, his eyes turned to the office bed. The sheets and quilt are relatively clean, and it is estimated that he has not been used several times.
　　 Xu Qiu locked the door, turned off the light, lay on the bed, did not enter the simulation laboratory, and soon fell asleep.
　　 Today's document reading and physical exercise tasks have not been missed.
　　 is really tired.
　　 From 1pm to 11pm, for ten consecutive hours, except for two sips of water in the middle, going to the toilet, and eating a meal, I never stopped.
　　 It is said that doing scientific research well is mental work, but the difference is physical work.
　　……
　　 The next day, Xu Qiu got up early in the morning, after having breakfast in Zhangjiang Canteen, he returned to the laboratory to start the experiment.
　　 Putting on his protective equipment, he walked to the fume hood and lifted the aluminum foil outside each reaction vessel to check the polymerization reaction.
　　As expected, the reaction time of about 12 hours, several polymerization reactions have almost proceeded.
　　 However, one of the three reaction flasks of Senpai did not look good, because no solid matter precipitated in the reaction flask.
　　 This reaction is one of the two reactions that Senior Sister herself voted, not Xu Qiu helped her vote.
　　 He guessed that the ratio of the materials to be fed was not 1:1, or that oxygen leaked into the reaction vessel and the catalyst was deactivated.
　　 This is also normal. The polymerization reaction requires very high material ratio and the catalyst is also very fragile. In many cases, it is difficult to determine which step has a problem, causing the experiment to fail.
　　 Xu Qiu carefully checked his own two systems, PBT4T and P2FBT4T.
　　 The former is similar to the results he observed in the simulation laboratory before, while the latter precipitates a lot of solid matter, which looks abnormal.
　　 At the beginning, he decided to use this 2TBT unit, which is a unit with two fluorine atoms attached to the BT unit, mainly based on the experience summarized in the literature.
　　 In order to ensure that the variables are as few as possible, except for the two introduced fluorine atoms, other conditions have not been changed, including the number and position of branches, etc.
　　According to existing literature reports, the introduction of fluorine atoms in the polymer donor has a high probability to improve its photoelectric properties.
　　Researchers often report individual cases and describe the advantages of introducing fluorine atoms from the level of experimental results.
"For example, it can improve the light absorption coefficient of the material, increase the carrier mobility, and improve the morphology of the blended film.
　　 However, no one has explained the role of fluorine atoms theoretically or at the molecular level.
"It is still unclear what kind of system is suitable for introducing fluorine atoms."
　　 However, this is also normal. Experimental science itself is based on experience. Many problems cannot be explained, so they can be used directly as theorems.
　　 Xu Qiu has roughly calculated before that more than 90% of the systems have improved performance after adding fluorine atoms, and the extent of the improvement varies.
　　 Of course, it may not actually reach 90%, because there must be many systems with reduced performance after adding fluorine atoms. Such articles have not been published.
　　 What is my own result, I still need to know after experimentation.
　　 But at present, it seems that there are some problems.
The solubility of 　　P2TBT4T is too low.
　　 But no matter what, the experiment must continue. The product is completely processed, the device is prepared, and the performance is tested. The result will naturally be clear.
　　……
　　 Xu Qiu added a blocking agent to the five reaction flasks in the third batch of reaction to start the blocking reaction.
　　 Then he returned to A501, turned on the computer, and prepared to search for documents.
　　 There are still a lot of documents in the field of organic photovoltaics. Even if Xu Qiu only reads the documents in the first and second districts, there are dozens of them in a month.
　　In a popular field like perovskite, there can even be hundreds of articles in a month.
　　 With such a large number of documents, it is unrealistic to expect to memorize everything in the documents. If the time interval is long, you can only remember a rough idea.
　　 Moreover, he will only read a summary and conclusion of most of the literature, and just look at the pictures. He will only read the whole article if it is published in the top journal or is very interested in the content.
　　 To find some experimental details this time, I need to read the literature again.
　　 Fortunately, "the predecessors planted trees, the future generations enjoy the shade."
　　 Before printing out the documents, Mr. Wei will also read the documents once, and summarize the abstracts, conclusions, and citation formats of the documents, and put them into WORD documents.
At the same time, in order to ensure that his students also read the documents carefully, he will send them paper documents and ask them to go to his office to tell him the main content of the documents after reading the documents, and sometimes ask some questions. .
Moreover, he also asked students to sort out the electronic version of the literature, put the screenshots of the title of the article, the pictures and tables in the text, and other notable points in one or several pages of PPT, and also mark the citation format of the literature for convenience Find it later.
　　 The previous literature in the field of organic photovoltaics was all taught by my senior sister, and she was also responsible for collating the PPT.
　　……
"For polymer donor materials, the main chain is a long conjugated structure, usually a conjugated aromatic ring, such as a benzene ring or a thiophene ring.
　　 The conjugated structure of the main chain can conduct positively charged holes well.
　　 In layman's terms, the main chain is like a "wire". The holes will be transferred along the "wire" from the inside of the film to the surface of the electrode ~EbookFREE.me~ and then collected by the electrode to generate current.
　　 The part outside the polymer main chain is called branched chain. This part is usually alkyl side chain. They are non-conductive and can be understood as the insulating rubber skin outside the "wire".
　　 However, the main function of this layer of insulation is not to insulate, but to make the polymer material soluble in solvents, to facilitate solvent handling, and spin-coating to form a film.
　　 If the branch chains are too large or too many, the photoelectric properties of the material will be reduced.
　　 This is because in the effective layer, the electron/hole pair must be split at the interface where the donor and the acceptor contact to form free electron and hole carriers.
　　 If the donor body is really wrapped like a wire, the donor body and the receptor will not be able to contact, there will be no way to form free electron and hole carriers, and no way to generate current.
　　 Therefore, under the premise of ensuring the solubility of the polymer donor material, the branched chain should not be too long.
　　……
　　 Xu Qiu opened the WORD and PPT files they organized.
　　 First search in WORD for polymer donor materials with fluorine (F) atoms, then find the corresponding article in the PPT, and check the title and picture.
　　 If it is worth reading the text, find the corresponding PDF document and read the full text.
　　 Xu Qiu mainly sees researchers comparing similar polymer donor materials with and without fluorine atoms.
　　 The results found that the polymer donor materials with multiple fluorine atoms reported by other researchers usually choose longer alkyl branches, which are generally a few to a dozen carbon atoms more than those without fluorine atoms.
　　 In his synthesis reaction this time, he did not modify the number of carbon atoms in the branch.
　　 Maybe this is the reason for the poor solubility of the product?