Chapter 64: Unexpected visitor

　　 It turned out that when Xu Qiu was spin-coating the perovskite film, his attention was focused on how to remove the white fog and obtain a uniform smooth film, while ignoring the difference between the transmission layer and the effective layer.
　　 The thickness of the perovskite effective layer film is usually above 200 nanometers, and the thickness of the general transmission layer material is preferably between 5-50 nanometers.
　　 Early organic solar cells did not have a transport layer. Later, researchers discovered that the introduction of a transport layer helped charge transport and improve the photoelectric performance of the device. This is how the transport layer was used.
　　 But when the thickness of the transport layer is too high, it will also increase the possibility of charge recombination, resulting in a decrease in device efficiency.
　　 This also explains why the performance of the device is higher than that of the perovskite transmission layer without the transmission layer, and the performance of the latter increases with the increase of the speed.
　　 Everything is because Xu Qiu applied the perovskite film too thick.
　　…………
　　 Back to the bedroom, Xu Qiu and Tao Yan said hello, then lay on the bed and entered the simulation laboratory.
　　 The solution in the simulated laboratory still keeps the state it was when he left last time, so there is no need to worry about the problem of deterioration of the solution.
　　 In the daytime experiment, the 4# sample has the highest efficiency, so it may be the most suitable for the transmission layer material among the four perovskite materials.
　　 Xu Qiu simply prepared 5 ml of 10% mass fraction of 4# sample solution directly as mother liquor.
After 　　, it can be directly diluted to obtain solutions of other concentrations.
　　Different from organic polymer materials, perovskite materials are small molecules, which dissolve faster and obtain more accurate concentrations, so it is easy to adjust the concentration.
　　 During the solution preparation process, he is also exploring the 0.5-2x speed function of the simulation laboratory.
　　 He discovered that after turning on the double-speed function, all the experimental instruments except for consciousness and his'body' can be in the double-speed state.
　　 When performing fine operations such as weighing medicines, he can adjust the time rate to 0.5 times to improve the accuracy of the operation.
　　 When you need to wait for ultrasonic cleaning, you can adjust the time rate to 2 times to speed up the experiment process.
　　The points consumed are calculated based on the actual time. When the 2x speed is turned on, 200 points will be consumed in one actual hour.
　　 In addition, he can also delineate the change of the time flow rate in a designated space.
　　 For example, he can get the ultrasonic cleaner at 2 times the speed and the glove box at 0.5 times the speed.
　　 As for the points consumed, the maximum speed in the entire space is taken, which means that as long as the instrument is turned on at 2 times speed, it will be consumed according to the points of 2 times speed.
　　 After some experience, Xu Qiu was very satisfied with this function.
　　 Next, he was going to experiment.
　　 In order to improve the efficiency of the experiment, Xu Qiu plans to only make devices with sample 4 as the transmission layer material.
　　 He did not plan to make PEDOT standard samples and samples without transmission layer, which is also his confidence in his operation.
　　 First, prepare the solution.
　　 The concentration of 10% mass fraction is used during the day, and the rotation speed is 2000-4000r.p.m., the thickness of the film obtained is obviously too high.
　　 Xu Qiu adjusted its concentration to 1%, 2%, 3%, 4% and 5% mass fraction.
　　 and then the speed.
　　Xu Qiu is unified to 5000r.p.m.
　　 This is basically the upper limit of the safe rotation speed of the homogenizer. If the rotation speed is increased, the substrate may fly out during high-speed rotation.
　　 Under normal circumstances, to obtain the same thickness of film, the quality obtained under the conditions of high concentration and high speed is better. Because the concentration is better to adjust, there is no need to change the speed.
　　The last is to control the interval time of the anti-solvent dripping.
　　 The result of a rough test during the daytime experiment is that there will be no white fog at 5 second intervals.
　　 Xu Qiu set an additional 4 seconds, 4.5 seconds, 5.5 seconds and 6 seconds.
　　 In this way, there are a total of 55=25 conditions.
　　 After confirming the experimental conditions, Xu Qiu started 2 times acceleration to make the solution dissolve quickly.
　　…………
　　 spin-coated perovskite transport layer and organic effective layer.
　　Evaporated calcium and aluminum electrodes.
　　 ready to test.
　　 When Xu Qiu is testing, the first piece is usually tested with a standard sample, or with the sample that he feels most promising.
　　 The purpose of measuring the standard samples is to judge the overall performance of this batch of devices. If the standard samples are lower than the average, the performance of the entire batch of devices may also be lower than the average.
　　 But he didn't make standard samples for this batch, and he didn't know which condition was better. It was completely unknown exploration, so he just took a sample, "1%, 5s".
After 　　 test, the efficiency is 8.66%.
　　 Seeing this result, Xu Qiu breathed a sigh of relief.
　　 This shows that my inference is correct, and it was really too thick before.
　　 Perovskite material can be used as a transmission layer, at least it has better performance than uncoated transmission layer.
　　It’s just that the efficiency has not reached 10%. Maybe the film at this concentration is too thin.
　　 He chose the "2%, 5s" sample and continued testing.
　　 Sure enough, the efficiency has increased, reaching 9.37%.
　　……
　　 After testing the remaining 23 samples.
　　Finally, the "3%, 5.5s" sample has the best performance.
　　The efficiency can reach 10.24%, which is equivalent to that of the PEDOT reference device.
　　 Leaving the simulation laboratory, Xu Qiu checked the time, and it was almost twelve o'clock.
　　 I forgot to take a bath in the public bathroom again today, so I can only take a shower in the corridor.
　　 The ice-cold water column hit him, and Xu Qiu not only didn't feel cold, but also excited.
　　He calculated the experimental plan for tomorrow:
　　 can further broaden the control range, for example, the solution concentration is 2.5%, 3%, 3.5%, and the speed remains unchanged.
　　 In addition, the other three solution systems can also be done. Although the probability of surpassing the 4# sample is not high, there may be miracles.
　　…………
　　 The next day, Xu Qiu went to the laboratory and was surprised to find that there was no one in the laboratory.
　　 swiped a card to open the access control. He checked his phone and realized that it was Saturday and the research team was not working.
　　 However, since it's all here, let's experiment.
　　 And, Saturday is good, no one will grab the glove box with him.
　　 He started the experiment according to yesterday's idea, and ordered takeout at the desk outside at noon.
　　 did not unexpected results.
　　 1, 2, 3# samples are not as good as 4#.
　　 Among them, the 2# sample is okay, and the highest efficiency is 9.6%, but it did not break 10%. After all, it is a little bit off.
　　The standard sample efficiency of this batch is 10.10%, and the highest efficiency in the 4# sample reaches 10.46%, the condition is 2.5% concentration, 5000r.p.m. rotation speed, 5.5 seconds interval.
　　 In fact, if the preparation conditions of the standard device are finely controlled as in the experimental group, the efficiency may be higher, but it is not necessary.
　　 This is also the unspoken rule of the industry. When the performance of the two is equal, the experimental group is made slightly higher than the control group, even if it is not much higher, but only 0.3%, it will look much more comfortable.
　　 At the end of the performance test, Xu Qiu heard the sound of someone coming from outside.
　　 does not seem to be the footsteps of Teacher Wei, who would it be?