Chapter 63: completely annihilated

　　 Xu Qiu opened the system panel.
　　【Scientific Research Support System】
　　 Permission level: 3
　　 Points: 9978
　　 Tasks in progress: 2
　　 Proficiency:
　　【Experimental operation class】
　　 Preparation method:
　　Cleaning the substrate (fourth-order 45%/fourth-order 80%)
　　 Solution preparation I (fourth order 40%/fourth order 50%)
　　 solution preparation II (fourth order 0%/fourth order 80%)
　　 spin coating I (fourth order 40%/fourth order 50%)
　　 Spin Coating II (50% third-order/80% fourth-order)
　　 Evaporation (4th-order 35% / 5th-order 0%)
Characterization methods:
　　Optical performance I (fourth order 40%/fourth order 80%)
　　Optical performance II (third-order 50%/fifth-order 0%)
　　Optical performance (fourth order 5%/fifth order 0%)
　　 charge transport performance (third-order 30%/fourth-order 40%)
　　【Instrument equipment tools】
　　……
　　【Special category】
　　 Literature reading (3rd level 1% / 4th level 50%)
　　 Weekly task II: Perform the experiment for more than 15 hours, and the duration of the simulation experiment is also recorded in the task. Current progress (0.5/15 hours), 500 points will be awarded for task completion.
　　 Advanced task: Publish an SCI paper as the first author. Task reward: 2000 points, authority level +1.
　　##
　　 Xu Qiu discovered that some of his skills were divided into two types, I and II.
　　 Class I is his copy of Chen Wanqing's skills on organic photovoltaics, and Class II is a copy of Wu Feifei's skills on perovskite materials.
　　 The upper limit of the proficiency of other general skills has also been increased. It seems that Feifei Wu's scientific research ability is indeed higher than that of her senior sister.
　　 System points have also accumulated close to ten thousand unknowingly, which should be of great use in the next experiment.
　　 After reading the panel, Xu Qiu turned on the auxiliary system to view the image of the "Spin Coating II" skill just copied.
　　 From the system image, the operation of anti-solvent spin coating is not difficult.
　　 First, evenly drop the prepared perovskite solution on the substrate, and then start the homogenizer.
　　 After about 4 seconds, use a pipette to quickly add toluene to the surface of the high-speed rotating substrate, and finally get a flat and smooth film.
　　 Wu Feifei said before that she meditated silently in her heart for 5 seconds before adding the anti-solvent. It seems that she meditated silently faster, and the actual time was only about 4 seconds.
　　 The system used by Xu Qiu is different from her, so it can only be used as a reference and needs to explore the conditions again.
　　 However, Wu Feifei uses the counting method in her heart to time the clock, which is a bit rough.
　　 Xu Qiu thought of a good way.
　　 While experimenting in reality, he can connect to the simulation laboratory and use the stopwatch inside to keep time.
　　…………
　　 Xu Qiu started to try, starting with 1# solution.
　　 In the first experiment, he set the stopwatch to count down to 5 seconds, and then simultaneously pressed the start button of the glue dispenser in reality and the stopwatch button in the simulation laboratory.
　　 Waiting for the second to return to zero, he quickly squeezed the toluene solvent from the pipette onto the surface of the substrate.
　　Because of his previous spraying experience, he has a very good control over the precision of this step.
　　 After spraying toluene, some changes can be clearly seen on the surface of the film, but because the substrate is still rotating at high speed, it is impossible to judge its specific morphology.
　　 After 30 seconds, the substrate stopped rotating and Xu Qiu picked it up with tweezers.
　　Unfortunately, the obtained film still showed a white haze, but the effect was slightly better than that of no anti-solvent.
　　 It seems that the addition of anti-solvent does work, but the conditions still need to be improved.
　　 Xu Qiu changed the interval to 6 seconds and tried again.
　　The white mist on the film obtained this time has deepened. It seems that the interval time should be shortened, not extended.
　　 Continue to adjust the interval time to 4 seconds.
　　 This time, I finally got a smooth and almost uniform film.
　　 Since the spin coating method of the perovskite material used is not spraying, it consumes about 80 microliters of solution each time. If you try a few more times, the solution will be used up.
　　 Therefore, Xu Qiu did not continue to fine-tune the interval time.
　　 Although compared with organic polymer materials, perovskite materials are not expensive, after all, they are small molecules with relatively simple structures and easy to synthesize.
　　 But lead iodide with a purity of 99.99% costs about one hundred yuan per gram, so it still cannot be wasted easily.
　　 Next, he explored the 2#, 3#, and 4# solutions respectively, and the optimal interval time for dripping the anti-solvent is between 3-6 seconds.
　　 After exploring the conditions, Xu Qiu prepared to make a batch of devices.
　　The problem faced at this time is the choice of device structure.
　　 One is the positive structure, then the perovskite material is used instead of PEDOT:PSS, the other is the inverted structure, then it is to replace the zinc oxide.
　　 The two structures cannot be vapor deposited together, so only one structure can be made at a time.
　　 He can't judge which structure is better, so he will start with the positive structure.
　　…………
　　Clean the substrate.
　　 Spin coating transfer layer.
　　 PEDOT: PSS substrate as a control group, spin-coated three pieces;
1# to 4# solution, each group also spin-coated three pieces of DMF solution with a concentration of 10% mass fraction, and the rotation speed was 2000, 3000, 4000r.pm, he directly took Wu Feifei’s conditions for spin coating the effective layer Used it as experimental group A;
　　 do not spin-coated the transfer layer, make a piece, as the experimental group B.
After 　　, Xu Qiu spin-coated the effective layer of PTB7-TH:PC[70]BM according to the optimal conditions, and evaporated calcium and aluminum electrodes.
start testing.
　　 He first tested the benchmark system, which is a sample based on PEDOT:PSS.
　　Three samples, the highest efficiency is 9.88%, 10.12%, 9.63%.
　　 Although the efficiency value fluctuates, this range is still within an acceptable range.
　　 Followed by the test of experimental group A, he picked up the "1#, 3000r" sample with full expectation.
　　 The first scan, the efficiency was 2.66%.
　　 Continue to scan, the efficiency is getting lower and lower, and finally stabilized at 2.50%.
　　 Xu Qiu shook his head and changed a piece of "1#, 4000r" sample.
　　 The highest efficiency is 2.74%, which is a drop compared to the first film, but it is of no use.
　　 Change the last 1# sample again.
　　 The highest efficiency is only 1.76%.
　　 "Maybe the 1# sample is not good, other numbers might have miracles." Xu Qiu comforted herself in her heart.
　　 But then, his heart became colder and colder.
　　 The remaining 2#, 3#, 4# samples, none of them have an efficiency of more than 5%.
　　 The sample with the highest efficiency is "4#, 4000r", but it is only 4.68%.
　　 Finally, he tested the samples of experimental group B, that is, the device without transmission layer material ~EbookFREE.me~, the efficiency is 5.52%, which is higher than that of all experimental groups A.
　　 This shows that after the perovskite material is coated, it has no positive effect at all, and it also reduces the performance of the device.
　　…………
　　 After the test, Xu Qiu checked the time. It was already past eight o'clock in the evening, and there was no time to make another batch of devices.
　　 After a day without any results, Xu Qiu returned to the desk in frustration.
　　 "How about, did the experiment go smoothly?" Chen Wanqing asked with concern.
　　 "Yes, the highest efficiency is only 4.68%, and the standard sample is 10%," Xu Qiu said depressed:
　　 "The most important thing is that the efficiency of uncoated transmission layer is 5.52%."
　　 "What about the device structure?" Chen Wanqing asked.
　　 "Positive structure, instead of PEDOT, once I shared four perovskite materials, it didn't work." Xu Qiu said:
　　 "Well, would it be that they are not suitable for hole transport layers? You can make an inverted structure and let them replace zinc oxide to see how the effect is." Chen Wanqing said:
　　 "Well, then I will try tomorrow." Xu Qiu said.
　　…………
　　 On the way back to the dormitory, Xu Qiu pondered over and over again in the experiment process today whether something went wrong.
　　 It stands to reason that the four perovskite materials he chose have a wide band gap, and the morphology of the coated film is also good. Why is the result so bad?
　　 He carefully recalled the experiment process and suddenly discovered a detail that he had overlooked before.
　　 "I understand!" Xu Qiu couldn't help calling out.
　　 With this roar, a pair of hugging lovers on the bench next to each other were separated.
　　 Xu Qiu made an apologetic gesture to them, then rushed back to the bedroom, ready to verify.