Chapter 280: A blessing in disguise

After the first draft of the graduation project was completed, Xu Qiuzheng was planning to further refine it. Qiu Heming came over at this time. This time he came alone and did not lead the younger brother like last time.
Wei Xingsi hosted Qiu Heming with tea at 218, and then summoned Xu Qiu, Wu Shengnan and Tian Qing.
After the three of them entered the door, Teacher Wei asked, "Are all the samples ready?"
"Ready," Wu Shengnan shook the petri dish in his hand slightly and replied proactively: "Including the P3HT standard sample, as well as two samples of organic conjugated polymer materials synthesized by myself."
"Okay," Wei Xingsi nodded and continued: "The results of P3HT are tested and tell me. I have literature data here. See if it can be matched."
As an old-brand conjugated polymer material, the performance of P3HT in all aspects has been deeply explored. As long as the experimental characteristics of the slight contamination are tested by various researchers, see if it is possible. , The data of fluorescence quantum yield is naturally available.
"It must be no problem. Each of our products has been tested before leaving the factory." Qiu Heming said confidently. After speaking, he unpacked a small cardboard box that he carried with him, removed several layers of bubble paper shockproof packaging on the inside, and took out the integrating sphere inside.
Xu Qiu took a closer look. The integrating sphere that Qiu Heming brought was the same in appearance from the pictures he posted earlier. The whole body is white plastic, which may have been made by direct firing with a mold.
The integrating sphere is designed to fit the sample compartment, but before use, you need to remove the sample card slot in the original sample compartment with a hexagonal screwdriver, and then install the special card slot for the integrating sphere.
After the equipment was debugged, Qiu Heming instructed Wu Shengnan to start the test, and Xu Qiu and Tian Qing were watching.
Soon, the first P3HT standard sample test was completed.
Qiu Heming exported the data, then copied an EXCEL file named "PLQY (Fluorescence Quantum Efficiency from the USB flash drive he carried to the computer desktop, and then opened the file.
This is a read-only file with several blanks for filling in parameters.
While processing the data, Qiu Heming introduced: "We manually input the data obtained by TRPL, and then we can directly fit and calculate the fluorescence quantum efficiency of the sample. For example, for this P3HT sample, the value of PLQY is..." Qiu Heming was stunned. For a moment, I wondered: "It's only a few percent, is this a photoluminescent material?"
"Oh, P3HT is an organic conjugated polymer with photoluminescence phenomenon, but it is not used in the field of photoluminescence. Now we mainly use it as the standard sample for testing, and the value pair will do. There is not much difference with the literature, so you can continue to test." Wei Xingsi's voice came from outside, and the TRPL instrument was placed in the utility room of his office, so he could hear each other.
Xu Qiu can understand the reason why the P3HT fluorescence quantum yield is relatively low, because it is a photovoltaic material, which is mainly used to convert light energy into electrical energy.
And if the fluorescence quantum yield of a material is high, it means that the absorbed sunlight energy is converted into fluorescence and the energy is conserved. If most of it is converted into light energy, then the part converted into electrical energy will naturally change. Less, most of the photoelectric conversion efficiency is not good.
After that, Wu Shengnan operated and tested several other samples of her, and the value of PLQY distributed between ten to thirty percent.
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These values ​​are high or not high, and low are not low.
After all, for some phosphors and other materials, it is possible that the fluorescence quantum efficiency exceeds 90%. Even some materials have a fluorescence quantum efficiency of more than 100% due to chain excitation, that is, absorb one photon and produce more than one photon. The extra photon is similar to the chain reaction of nuclear fission. The three fluorescent photons generated by the excitation of sub-fluorescence photons.
However, her materials are mainly electroluminescent materials, and the data of PLQY is not important. Wu Shengnan mainly studies the fluorescent color changes of her materials under different voltages, and the response time of the color changes.
The main thing that needs to be characterized by PLQY is the perovskite quantum dot material, but she has not yet successfully synthesized it.
Objectively speaking, the preparation of quantum dot materials is indeed difficult, because quantum dots are zero-dimensional dot-shaped nanoclusters, and the scales in three dimensions must be at least less than 100 nanometers.
Quantum dots of different materials have different scales. Some scales are less than 100 nanometers, while others need to be less than 20 nanometers or 10 nanometers. There is no unified standard for the scale of materials, mainly to see whether the material has quantum effects. If there is a quantum effect, it is a quantum dot; if there is no quantum effect, it is an ordinary cluster of atoms/molecules.
It is easy to imagine that this kind of quantum dot material with a scale of a few nanometers and tens of nanometers has a high specific surface area, and the surface activity of the material is very high, and it is prone to chemical reactions or agglomeration, so it is very unstable.
The surface is usually connected to a ligand or passivation layer, like the oleic acid surfactant used by Wu Shengnan before, to allow the perovskite quantum dot material to maintain the state of quantum dots without agglomeration. Unfortunately, she used the solution method and heat The injection methods all failed.
Wu Shengnan decided that the heat injection method was more promising, and he was ready to continue trying.
After the samples were tested, Tian Qing, Wu Shengnan and others discussed some TRPL testing issues with Qiu Heming. Xu Qiu did not join in the fun, after all, he had copied Qiu Heming's skills.
"Dr. Qiu, stay and have a casual meal?" Wei Xingsi said in a courtesy: "I have troubled you during this period of time. I personally ran over twice."
"Yes, I'll go home and eat." Qiu Heming waved his hand and declined. He also settled in the Demon Capital, but he was not a native, but the "Magic Drift" took nearly 20 years to take root.
At around five o'clock, Chen Wanqing returned to Handan campus. After returning to 216, she took out a garbage bag from her schoolbag, which contained her synthesized materials and intermediate products, and walked towards the laboratory.
Xu Qiugai got a little headache after changing his graduation design, so he followed her into the laboratory and spoke up: "Senior sister brought so many bottles back, it’s a good harvest."
"It's okay," Chen Wanqing replied while operating in the glove box: "This time I synthesized two receptor materials, IDT-BT-ICIN and IDT-T-ICIN. Originally, I planned to synthesize only one. Yes, the experiment failed one time later. In order to prevent that there was nothing to report during the meeting, another thiophene (T) unit was added to the original BT unit."
"That's it." Xu Qiu nodded. Her two materials were copied to Simulation Lab II, and the simulation experimenters were arranged to optimize the performance. Then she asked casually: "Do you plan to continue the synthesis next week?"
"Stop for a while and make the device." Chen Wanqing chuckled and laughed at herself: "Now I feel like I'm almost pickled by organic solvents. I have to slow down so that my body can metabolize the organic solvents absorbed during this time. Get out."
"Sounds quite reasonable." Xu Qiu still agrees with the senior sister's point of view.
According to his understanding, the human body's immune system is very powerful, and the small amount of toxic and harmful substances ingested can be gradually eliminated through normal metabolic processes.
Of course, just like a firewall, the immune system has limits and loopholes.
The so-called "limit" means that for toxic substances exceeding a certain dose, due to the problem of the immune system's processing speed, it may have caused irreversible damage to human organs and tissues before they are completely eliminated.
The "loophole" is that heavy metals have an enrichment effect, and the fluorine element is stable in combination. Once they are ingested into the body, they will increase and it is difficult to eliminate them. In fact, the immune system is not incapable of processing them, but the processing speed is relatively slow. In theory, if you stop taking them, the content of these elements in the body will definitely be less and less until one day tends to be safe. However, this time span may exceed the life span of normal human beings. For example, it takes hundreds of years or thousands of years. It is a bit similar to "As long as you die, your illness will be cured."
The next day, early Saturday morning, Xu Qiu got the device results of the senior sister system.
The IDT-BT-ICIN system, whether it is matched with narrow bandgap polymer donors such as PCE10 and PCE11, or with wide bandgap polymer donors such as H11, H12 and H13 developed by Xuemei, the device performance is not good. , The highest efficiency is only 2.8%.
Instead, the highest efficiency of the IDT-T-ICIN system reached 6.1%, and the optimal donor material was H13, which was equivalent to the previous IDT-ICIN system.
Xu Qiu thought about it and found a further optimization direction, which is to modify the side chain of the newly introduced thiophene unit, mainly because the newly introduced thiophene unit increases the conjugation length of the molecule, but there is no new side chain, and the solubility is slightly Some pressure.
One method is to directly add an alkyl side chain, such as a short dendritic side chain such as 2-ethylhexyl, which only improves the solubility without greatly affecting the light absorption performance and energy level structure of the acceptor molecule. ~EbookFREE.me~ Another method is to introduce heteroatoms at the same time as side chains, such as side chains with oxygen and sulfur heteroatoms. This will have unpredictable effects on the performance of the molecule, or better Or bad, but anyway, it can be used as a potential optimization direction.
As for the BT system, the efficiency base is too low, and Xu Qiu is not sure whether it can be saved, and is not interested in it for the time being.
After the analysis was completed, Xu Qiu thanked the senior sister in her heart. Her experiment failed halfway, and it was a blessing in disguise. Additional IDT-T-ICIN materials were synthesized. If you refer to the article "Nature·Materials", you can go to the black , If you only synthesize IDT-BT-ICIN, you will probably cry again at the group meeting.
After all, there is no difference between the efficiency of more than two o'clock now and the efficiency of less than 1%.
PS: When counting the words of the chapters at the starting point, the English letters and special symbols together count as one word, which means that the names like "IDT-BT-ICIN" are very long, but the number of words is actually 1. Suddenly remembering this, I will explain that the name is not so long because of the number of water characters, but in fact, when doing scientific research, the material is named like this.