Chapter 29: Can you spin coating like this?

　　 Xu Qiu went to the cafeteria for dinner with her senior sister and Tian Qing.
　　 "Chen Wanqing, where do you think I should go for my graduation trip?" Tian Qing asked.
　　 "Hmm..." Chen Wanqing thought for a while and said, "How about Sichuan Province?"
　　 "It's not so good, I am not used to spicy food." Tian Qing turned around and asked, "Xu Qiu, do you have any suggestions?"
　　 "Tibet province?" Xu Qiu said.
　　 "Tibet, I heard that there will be altitude sickness, it is too dangerous." Tian Qing said.
　　 "How did Senior Sister Tian Qing think of going on a graduation trip?" Xu Qiu said.
　　 "The senior year holiday is the last long holiday. After graduation, there is no two-month holiday like this," Tian Qing said, spreading his hands and saying:
　　 "The winter and summer vacations of graduate students are generally two weeks to one month, and our group is the one that only has two weeks."
　　……
　　 After dinner, Xu Qiu returned to the laboratory and continued to work.
　　 The vacuum level has reached the standard. He carefully operated the main console of the evaporation machine. After all, he had only operated this machine twice, and he was not skilled enough.
　　 Fortunately, no accidents happened.
After 　　 was over, Xu Qiu glanced at the vapor deposition proficiency and reached 70% of the third level. It should be the fourth level after another time.
　　 Looking at the shining silver substrate in front of him, Xu Qiu has the feeling that his parents look at their children.
　　 Raised you up (done), you have to fight for me.
start testing.
　　 The first film, labeled "DCB, 1200", is a substrate under the benchmark conditions, and the conditions are the same as the batch made by my sister on Sunday.
　　 six points, the highest efficiency is 4.18%, and the average efficiency is 4.03%.
　　 It’s not good to be a teacher. At that time, the highest was 4.4%, but this time it was only 4.18%.
　　 Could it be that which experimental step went wrong?
　　 Xu Qiu couldn't help but start to doubt.
　　 Continue testing.
　　 The second film, the highest is 4.12%.
　　 The third piece, the highest is 4.23%.
　　 The fourth film, the highest is 3.88%.
　　……
　　 The twelfth piece, the highest 3.92%.
　　……
　　 are all samples prepared by the normal spin coating method, and the efficiency is lower as measured.
　　 Every time a piece is tested, Xu Qiu's heart becomes cold.
　　 And he found that after spending 500 points before, the skill of the glue machine learned from the system is not effective at all. The performance of the device is not improved by the low speed and then the high speed.
　　 There are only nine devices made by spraying, and Xu Qiu doesn’t have much hope for them.
　　 He grabbed a piece of substrate labeled "DCB, 1200, P" and started testing.
　　 "drop."
　　 After hearing the sound of the end of the voltage scan, Xu Qiu glanced at the efficiency.
　　4.70%!
　　 looked at it carefully again, and it was correct.
"I!"
　　 Xu Qiuqing couldn't help but yelled out, waved his fist in the air, and hit the glass inside the glove box.
　　 "Ah! It hurts." Xu Qiu took a breath. Fortunately, the glove box was relatively heavy and the shock absorption performance was very good, which did not cause an experimental accident.
　　 "Xu Qiu, what's the matter with you?" Chen Wanqing asked with concern when he heard his shouting.
　　 "It's okay, I stepped on my own foot just now." Xu Qiu decided to wait until all the tests were completed before notifying the senior sister of the results.
　　 He has a hunch that there may be higher numbers later, maybe it can exceed 5%.
　　Finally, the highest efficiency of this substrate is 4.73%.
　　 He changed the dichlorobenzene solvent again, and the highest values ​​of the substrates at the other two speeds were 4.62% and 4.55% respectively.
　　 Although they all surpassed the senior sister’s previous highest value of 4.5%, there is still a certain gap from the 5% required to complete the task.
　　 Then test the chlorobenzene group.
　　 The results are not satisfactory. The highest efficiency at the three speeds is 4.10%, 4.22% and 4.28% respectively.
　　 In the end, there are only three chloroform solvent substrates left. Can it bring a miracle?
　　 The first film, "CF, 1000, P".
　　After installing the substrate and pressing the start button, Xu Qiu stared at the computer intently, waiting for the result.
　　4.80%.
　　 There is a play!
　　 Xu Qiu cheered secretly and continued the test.
　　 Finally, the highest value was 4.84%.
　　 The second piece, "CF, 1200, P", the highest value is 4.92%.
　　 The last piece, "CF, 1500, P".
　　 You have to work hard.
　　 After Xu Qiu clicked to open, he closed his eyes, and did not open his eyes until he heard the end of the scan.
　　 Take a closer look, 4.95%.
　　 Continue scanning, 4.98%, 4.94%, 4.97%, 4.88%, 4.93%,...
　　 The highest value is 4.98%.
　　 scanned a few other points, and there is no higher value.
　　 In general, when the film is uniform, the efficiency of the first point is usually the highest, because only it is tested from the initial state, and when it is irradiated, other points will also be illuminated by light.
　　…………
　　 Do you want to me like this? It’s 0.02% short.
　　 Xu Qiu returned to the desk with a disappointed look.
　　 Chen Wanqing saw Xu Qiu's appearance and comforted: "Xu Qiu, it's normal for the experiment to fail. When I first debugged the equipment, I was so happy that I could have 1% efficiency."
　　 Then, she asked: "That's right, what is the highest efficiency of the schoolboy today?"
　　 "4.98%." Xu Qiu replied feebly.
　　 "How much?" Chen Wanqing thought she had heard it wrong, and asked again.
　　 "4.98%." Xu Qiu said.
　　 "Really?" Chen Wanqing stood up excitedly and almost hit Xu Qiu's body.
　　 "Senior sister, slow down." Xu Qiu was afraid that she would fall, so he helped her.
　　 "Quickly, show me your data." Chen Wanqing pulled his sleeve and walked into the laboratory.
　　 "Isn't it 4.98%," Xu Qiu said: "Senior sister, go slow, I'm thinking about how to find a way to get it above 5%."
　　 "Tell you the easiest way to keep two significant figures, rounding up to 5.0%." Chen Wanqing joked.
　　 Xu Qiu is speechless. It is true that you can do this to write an article for the sake of beautiful data, but the system does not recognize this method if you have to complete the task now.
　　 Seeing that he didn't speak, Chen Wanqing said, "Tell me about the experimental conditions."
　　 "Chloroform solvent, 10 mg/ml, P3HT:PC[60]BM, mass ratio 1:1, speed 1500r.p.m., solvent annealing, thermal annealing, evaporation and other conditions have not changed." Xu Qiudao.
　　 "Do you have other speeds?"
　　 "I also made 1000 and 1200 rpm, the efficiency was 4.84% and 4.92% respectively."
　　 "Ah! I thought about it." Xu Qiu suddenly said with excitement.
　　 "I...I also thought of it." Chen Wan said weakly, "Then you talk about it first."
　　 "Now that the efficiency and speed are positively correlated, the extreme point may not be 1500r.p.m., but higher, so a batch of substrates under high speed conditions, such as 1800, 2000, 2500r.p.m., can be made."
"Well, it's similar to the method I thought of. How did you do it?" Chen Wanqing wondered; "I also tried chloroform and chlorobenzene solvents before, and finally found that dichlorobenzene works best. "
　　 "Naturally, special skills are used. Sister-in-law will come over and I will show you." Xu Qiu said.
　　 Then, he entered the glove box and demonstrated the spraying method to the senior sister.
　　 "Is it still possible to spin coat like this?" Chen Wanqing's mouth opened into an O shape and exclaimed.