I Have a Research Support System

Chen Wanqing led Xu Qiu to a black experiment table beside him, on which there were three instruments and a computer.

These three instruments are UV-Vis Spectrophotometer, Fluorescence Spectrometer, and Electrochemical Workstation. She introduced them and pointed them to Xu Qiu.

The first two instruments are mainly used today, and they can be used to obtain the light absorption spectrum and fluorescence spectrum of thin film samples, generally referred to as UV-vis and PL.

Chen Wanqing turned on the power of the UV-Vis spectrophotometer and the fluorescence spectrometer, and then turned on the UV-vis testing software in the computer.

After waiting for a few seconds, the computer shows that the connection with the instrument is successful, and the control page pops up at the same time.

Chen Wanqing explained while operating:

The testing principle of UV-vis is to pass the monochromatic light of each wavelength through the sample respectively. During this process, part of the photons are absorbed by the sample, and then the intensity of the incident light and the outgoing light are tested, and the wavelength of the sample can be obtained by calculation. light transmittance.

The range we can test is roughly 200-1000 nanometers.

The experimental steps are also very simple.

The first step is to start the light source;

The second step is to test a blank sample, that is, a glass piece, stick it on the sample table, and click the 'blank' button;

The third step is to test the sample, which is also pasted on the sample table, click the 'sample' button, and the software will automatically test and subtract the background.

This instrument can also be used to test solution samples, but we usually use it to test thin films.

The test speed is very fast, and the light absorption spectrum of the sample appears on the computer screen, and the main absorption peak is at 400-650 nanometers.

Xu Qiu still didn't understand the notation, so he asked, Senior sister, what's the matter, is your guess correct?

Hmm... Chen Wanqing thought about it for a while, and said, From this map, compared with the sample under normal spin-coating conditions, the half-width of its absorption peak is now smaller. If its light absorption coefficient is also If it is improved, it can be explained by the increase of polymer crystallinity, but the film thickness is not known, so the light absorption coefficient cannot be calculated.”

Then how to measure the film thickness? Xu Qiu asked.

The thickness of our spin-coated organic films is generally about 100 nanometers, and their thickness is usually measured by ellipsometer or SEM.

The former needs to fit the parameters, while the latter needs to break the substrate under the condition of liquid nitrogen cooling, and then test the SEM of the section. Evidence because it's not intuitive enough.

If you want to get more intuitive evidence, you still need to go to the Modu Synchrotron Radiation Center and do a grazing X-ray diffraction experiment on the sample.

Chen Wanqing finished measuring the other five samples, saved the data, and said:

After the fluorescence spectrometer is turned on, it needs to warm up for a while, and it should be almost ready now.

She opened the instrument cover of the fluorescence spectrometer, took out the sample holder inside, pasted one of the samples and put it back, and continued:

Its principle is to irradiate the surface of the sample with monochromatic light, the sample molecules absorb the energy of the photons and emit fluorescence, and the instrument collects the fluorescence signal.

According to the principle of energy conservation, under single-photon excitation, the energy of fluorescence is less than that of excitation light, that is, the wavelength of fluorescence is longer than the wavelength of excitation light.

The instrument has two modes, one is to collect the fluorescence signal of the sample at all wavelengths within the detection range of the instrument at a given wavelength of the excitation light;

The other is given a range of excitation light wavelengths and collects sample fluorescence signals at given wavelengths.

We use the first mode. Usually, the wavelength of the excitation light is selected to correspond to the peak in the sample light absorption spectrum.

Therefore, it is generally necessary to test UV-vis first, and then test PL.

Chen Wanqing opened the PL test software and began to set the parameters: the excitation light wavelength is 550 nanometers, and the fluorescence detection range is 570 to 850 nanometers.

This does not require a blank substrate, just a direct measurement. The limit test range is roughly 300-850 nanometers.

The operation is very simple, put the sample in, rotate the sample stage so that the sample and the excitation light source form an angle of 60 degrees, then close the lid, and start the test.

Chen Wanqing pressed the start button.

Woo--

When, when, when...

The sound of this instrument is quite unique. Xu Qiu said.

It should be the sound of the transmission device and the grating inside, Chen Wanqing said, Have you learned how to operate these two instruments?

I learned it. Xu Qiu nodded, and at the same time copied the two skills of the senior sister in the system.

Now, he has more than twenty skills in his system list.

…………

Xu Qiu continued to experiment, and today he has to make another batch of devices, another day of overtime work.

Clean the substrate and spin-coat zinc oxide.

During the annealing interval of the zinc oxide substrate, the senior sister came over to use the glove box for a while, and prepared chloroform solutions of P3HT, PC[60]BM, and PC[70]BM respectively.

After the senior sister finished it, Xu Qiu continued to spin coat the effective layer.

The only variable this time is the rotation speed, so he only prepared 12 substrates, designed six sets of rotation speeds, and made 2 pieces in each group.

The speeds are 1200, 1500, 1800, 2000, 2300, 2500r.p.m. respectively.

After some operations, a piece of 1200-rpm was scrapped.

But the problem is not big, today's focus is on samples above 1500 rpm.

He transferred the substrate to the evaporation chamber and started vacuuming.

Back at the desk, Xu Qiu saw that her senior was processing the data she had just measured, so she moved over curiously.

As for drawing pictures, isn't Teacher Wei very strict about this? Xu Qiu said.

Yeah, he pays special attention to the style of the picture, such as:

For the font and font size, use size 36 for physical quantities and units, use size 26 for numbers on the coordinate axes, use Song typeface for Chinese, and use Times New Roman font for English. Chinese characters cannot appear in pictures;

For the scale of the coordinate axis, there must be coordinate axes on the top, bottom, left, and right sides, there must be scales on the left and bottom, no scales on the top and right, and the sharp point of the scale must point into the figure;

The legend cannot use the default black box, and must be manually changed to no border;

When there are multiple curves in the picture, the curve of the control group must be black, and the curve with the best data in the experimental group is red.

Besides that, there are many other details to pay attention to. Chen Wanqing said.

Senior sister can remember so many requests. Xu Qiu said.

Practice makes perfect. In the beginning, basically every picture had to be changed, Chen Wanqing said, Later, I used the template function of Origin software for all types of pictures and saved the templates. Now I directly apply the templates. The odds are much smaller.

Sister, you understand. Xu Qiu stretched out his hand and said.

What? Chen Wanqing pretended not to understand.

Template, origin, senior sister, your acting skills are too exaggerated. Xu Qiu laughed.

Oh—— Chen Wanqing also smiled and said, It's easy to say, when you want to draw a picture, I will pack a copy for you.