I Have a Research Support System

"Ring ring ring."

At eight o'clock in the morning, the phone alarm clock rang on time.

Xu Qiu quickly turned off the alarm clock, lay on the bed for a minute, and then straightened up and sat up.

He looked at the other two bunks. Tao Yan had already left the dormitory, and Ren Bin was still soundly asleep.

Picking up the phone casually, unlocking the screen, among a long list of messages pushed by various applications, there is a WeChat message from Teacher Wei.

"Got it, thank you for your hard work." The other party replied with the bunch of pictures of the equipment he had taken before.

Xu Qiu looked at the time when the message was sent, it was after one o'clock in the morning, it is estimated that Teacher Wei had just arrived at the hotel at that time.

Instead of replying to Teacher Wei, he sent "Good morning" to Han Jiaying, and then went to wash up briefly.

After washing up, the junior girl still hasn't replied to the message. Xu Qiu judged that she must have not gotten up yet, after all, the two of them stayed until the early morning last night.

So, he went to exercise early and eat breakfast alone.

At about nine o'clock, Xu Qiu received a message from Han Jiaying:

"Good morning~"

"^(*￣(oo)￣)^"

"what is this?"

"pig."

"You're a pig."

"Bounce."

"Bounce back."

"Shut up, get up quickly."

"Just make trouble, hum!"

Xu Qiu was chatting with the junior girl while walking towards Caiyi. He mainly typed, and the junior girl mainly spoke. The girl's voice was three parts lazy, three parts arrogant, and four parts soft, It sounds like an old fan chart.

Han Jiaying didn't stay in bed for too long. After all, she had a lot of experimental tasks today. On the one hand, she had to test whether the microwave reactor was easy to use, and on the other hand, she also had to deal with the two reactions that Xu Qiu submitted yesterday.

"Get up, I'm going to wash up."

"Good, let's go."

Xu Qiu arrived at Caiyi 216 at about 9:30. He found that the laboratory hadn't opened yet, and he was the first to come.

He shook his head, opened the door with his card, entered the inner laboratory, and checked the 8 disposable centrifuge tubes with sample copper mesh prepared a few hours ago, each containing 2 samples of the same system.

Xu Qiu confirmed that the water in the centrifuge tube and the copper grid of the sample had completely dried, and packed them all away in a plastic bag.

When he came downstairs to Caiyi, he happened to meet Sun Wo who had just come by by bike, greeted him, and then walked towards the aging building with ease.

The scheduled TEM test time today was ten o'clock, and he arrived at the TEM test room about ten minutes earlier. The students in the previous group hadn't left yet, and they were testing the last sample.

After waiting for a while, it was finally Xu Qiu's turn.

The teacher in charge of the test was the same as last time, and he didn't talk too much. The other party briefly asked Xu Qiu about the type of sample, and started to put on samples if he wanted to get any information.

Cool with liquid nitrogen, pump the vacuum, turn on the camera, and start the test.

The two exchanged shooting locations, took pictures, zoomed out, continued to take pictures, continued to zoom out...

Zoom in on the screen, change the location, and repeat the previous step.

Replace the sample and repeat the above three steps.

U disk to copy the data, pat the ass and leave.

Although the final data obtained from the TEM test is a set of bitmap images in .bmp format, which need to be manually cropped and image processed, the images can also be viewed in real time directly through the computer screen during the test.

When leaving the testing room, Xu Qiu had already completed the preliminary analysis of the data in his mind.

There are four sets of conditions, and the TEM images are different:

1#, pure chloroform solvent condition, blends very well with receptors, almost no aggregation area of ​​PDI;

2#, under the condition of chloroform + DIO, the blending of receptors is better, and there is a small amount of PDI aggregation area;

3#, under pure chlorobenzene solvent conditions, a certain degree of phase separation occurs for the acceptor, and there are obvious PDI crystal phase regions;

4#, under the condition of chlorobenzene+DIO, the donor acceptor has obvious phase separation, and a large number of PDI crystal phase regions are produced.

Different solvent treatment conditions correspond to different device performance. According to the conclusions drawn in the previous simulation laboratory, 2# is the best, 1# is the second, 3# is the second, and 4# is the worst.

The corresponding relationship between the performance of the device and the blended morphology is in line with the general theory of blended morphology in the field of organic photovoltaics, that is, the best blended morphology of the effective layer is a bicontinuous three-phase structure, and the blended morphology of 2# The best, so the corresponding device performance is also the best.

The so-called bicontinuous three-phase structure refers to the three phase regions of the donor aggregate phase, the acceptor aggregate phase, and the donor-acceptor blend phase. Among them, the two aggregate phases need to present a bicontinuous structure throughout the entire The effective layer is about 100 nanometers in size, used to generate excitons and transport free electrons/holes to the electrode; there is a blended phase at the junction of the two aggregated phases, which also generates excitons, but the main function is Split the excitons, form free electrons/holes, and then transfer them to the acceptor-aggregated phase/donor-aggregated phase, respectively.

In the field of organic photovoltaics, there are five main steps in the entire photoelectric conversion process:

Exciton generation, the first step in converting light energy into electrical energy, the optoelectronic material absorbs photons and is excited to form electron/hole pairs bound by Coulomb gravity;

Diffusion of excitons, transfer of bound electron/hole pairs to the donor-acceptor blend phase;

Exciton splitting, the bound electron/hole pairs are split at the donor-acceptor interface and become freely movable electrons/holes, which stay in the acceptor/donor phase respectively, and part of the energy will be lost during the process ;

Free charge transport, driven by the built-in electric field, free electrons/holes move in the direction of the two electrodes in the acceptor/donor aggregate phase;

The free charges are collected by the electrodes. In the absence of an external load, the two electrodes collect electrons/holes, namely negative/positive charges, to form a potential difference. If there is an external load, a photocurrent is formed.

The three-phase structure undertakes the first four of these five steps, and the importance of the blend film morphology is evident.

This is also the reason why the performance of the final battery device is different when using the same photoelectric material under different device processing conditions.

Xu Qiu left the aging building, took a few steps outside, and came to the fourth teaching building next to it, randomly found a classroom that was not in class, and walked in.

There were a few self-study students in the classroom, and Xu Qiu's appearance did not cause any disturbance.

Xu Qiu glanced at their textbooks.

Hey, "Advanced Mathematics B".

It should be freshman students, stay in the classroom to review after the first and second classes.

Xu Qiu reasoned casually in his heart, then got down on the seat near the door and pretended to sleep, and entered the simulation laboratory II.

Based on the results of this TEM test, he got several main conclusions:

First, for the two optimal 3D-PDI systems of Xu Qiu and Han Jiaying, the intrinsic crystallinity of PDI molecules can be greatly suppressed under the conditions of low-boiling point chloroform solvent treatment.

Second, the PDI non-fullerene acceptor system is different from the traditional polymer donor/fullerene derivative acceptor system. The blending morphology of the former effective layer is greatly affected by the processing solvent. Xu Qiu speculates that it may The reason is that the former is crystallization dominated by small molecular materials, and the latter is crystallized dominated by polymer materials.

Third, DIO, a solvent additive with a high boiling point, will prolong the time for the effective layer solution to be converted into an effective layer film, thereby improving the crystallinity of 3D-PDI molecules and increasing the number and size of PDI crystal regions.

Fourth, comparing the two main solvents of chloroform and chlorobenzene, the boiling point of chloroform is lower than that of chlorobenzene, so the chlorobenzene solvent system in the initial state is more likely to induce crystallization of 3D-PDI molecules and form crystal regions.

Among these conclusions, the second one provides new ideas for the next experimental optimization:

Since the blending morphology of the effective layer will be greatly affected by the processing solvent, it is necessary to strengthen the exploration in this area.

Xu Qiu quickly planned the experiment, taking the pure chloroform system as the reference point (at this time, the crystal region of PDI is almost 0), imitating the previous optimized route of the chloroform/DIO system, and introducing various high boiling point solvents as solvents Additives (number of PDI crystal domains, increase in size).

Then, he quickly gave instructions to the simulation experimenters to explore the chloroform/chlorobenzene system, chloroform/dichlorobenzene system, chloroform/chloronaphthalene system...

...

In the afternoon, Xu Qiu supplemented the HOMO/LUMO energy level tests of two 3D-PDI systems.

Although he has developed three generations of 3D-PDI molecules this time, Xu Qiu does not intend to split the three generations of molecules into three articles and publish them like the previous PCE11 system.

On the one hand, if it is to be split into three articles, it must be published in the order of the first, second, and third generations, and there is a possibility of being cut off by others in advance.

On the other hand, this kind of dismantling and development of articles may end up with an ordinary first-section plus two second-section articles. The number of articles has increased, but the quality is not as good as an NC, not to mention editing or other research work Risk of not buying it.

If it is a graduate who lacks articles, it is understandable to do this, but Xu Qiu has no shortage of articles now, so there is no need to do so.

After completing the HOMO/LUMO energy level test, Xu Qiu put the existing characterization data in a PPT file for summary.

If you don’t summarize, you don’t know. Once you summarize, you will be shocked.

He was surprised to find that the characterization data of the two optimal 3D-PDI systems of him and his schoolmate have basically been assembled:

Light absorption performance, including light absorption spectrum UV-vis, fluorescence spectrum PL, transient fluorescence spectrum TRPL, all tested;

The HOMO/LUMO energy level test has just been completed;

Molecular structure related, including nuclear magnetic resonance NMR hydrogen spectrum, carbon spectrum, elemental analysis, the sample has been sent, and the original data can be obtained after waiting a few days;

DFT simulation, the test is completed.

Photoelectric performance, bright state/dark state J-V characteristic curve, external quantum efficiency curve EQE, the test is completed, of course, if the efficiency reaches a new high in the future, a new one needs to be drawn;

Morphological characterization, transmission electron microscope TEM, test completed.

There are only a few characterization tests that are missing now, such as CELIV in terms of charge transport mechanism, GIWAXS for molecular packing structure characterization, and atomic force microscope AFM, and perhaps an SCLC.

Next week, I will spend one or two days to get CELIV, AFM, and SCLC done. After two weeks, I will go to the light source and test GIWAXS again, and the data will be completed.

In this way, the article can be written.