I Have a Research Support System

Sunday.

Xu Qiu came to the laboratory.

Duan Yun was wearing earphones and concentrating on typing, while Chen Wanqing was sorting out paper documents on the table.

Xu Qiu greeted Duan Yun first, then went to sit next to Chen Wanqing.

"Sister, is there any news about the PEN base?"

"Well, I have contacted several manufacturers of optoelectronic materials, and one of them has ready-made PEN substrates," Chen Wanqing said, "But they only make large-area substrates, and they must buy at least 1 meter by 10 meters. I bought it according to the specifications, and it is estimated that it will arrive within a week.”

"Large-area substrate," Xu Qiu asked, "referring to a whole PEN substrate with an area of ​​10 square meters, is it evenly coated with ITO?"

"That's right." Chen Wanqing said.

"But the ITO on the glass substrate we use has patterns." Xu Qiu said.

"Then it is necessary to cut the large substrate into small pieces of one square inch, and then etch away the unnecessary ITO to obtain a patterned ITO substrate." Chen Wanqing said.

"Okay, I understand," Xu Qiu said, "Does senior sister have ready-made etching conditions?"

"It seems not." Chen Wanqing tilted her head and thought for a while.

"Like?" Xu Qiu murmured in his heart, and said, "Okay, then I'll look for it."

He took out his computer and looked through the documents on flexible substrates again.

Soon, he saw the conditions for etching ITO given by them in the experimental information section of one of the documents:

Add zinc powder to 2 moles per liter of dilute hydrochloric acid, and then put it into an ITO substrate, and the part in contact with the solution will be etched away.

However, the PEN/ITO substrate has not yet arrived, so he can only write down this method first, and then report to Chen Wanqing:

"Sister, I have found an etching method for ITO."

"I found it so quickly, let me have a look." Chen Wanqing leaned over and looked at Xu Qiu's computer.

"I remembered, this is the classic wet etching method, I remember there is also a dry etching method..." Seeing Xu Qiu staring at her, Chen Wanqing whispered:

"Would you believe me if I said I really didn't think about it just now?"

"I believe." Xu Qiu spread his hands helplessly.

…………

There is no experiment to do today, so Xu Qiu wandered around the laboratory, wanting to see if there are any other instruments that he is not familiar with.

As a result, he was surprised to find that in the entire laboratory, except for the electrochemical workstation, there was only one instrument that he had not used.

He still had a vague impression of that instrument, as if it had appeared in Tian Qing's graduation defense PPT.

Considering that after the exam week starts next week, he will not come to the laboratory for nearly a month, so Xu Qiu decided to get the instrument done today.

So, he found Chen Wanqing.

"Sister, what is that instrument in the laboratory used for? Can you teach me?"

"That one is used to test CELIV and TOF," Chen Wanqing said, "It's mainly used by Tian Qing, and her graduation project is for this.

However, Mr. Wei also taught other people the test method, and I can also operate it, but I am not very good at data analysis.

The two instruments are mainly used to characterize the transport of carriers in battery devices, and they are more biased towards theoretical research.

By building models and fitting data, it is said that a lot of information about the kinetics of charge transport can be obtained.

But now I will simply calculate the carrier mobility.

In the field of semiconductors, electrons and holes are called carriers, and their mobility can be understood as the speed at which they move in the device, usually the faster the better.

I haven't used this instrument since I learned it. If you hadn't reminded me, I wouldn't have thought of testing it. "

"Before the test, let me show you a baby." Chen Wanqing said mysteriously.

"Baby?" Xu Qiu followed the senior sister suspiciously, and her direction of travel was a locker.

Chen Wanqing took out a black square paper box from the locker and signaled Xu Qiu to open it.

After Xu Qiu opened it, he found two black zipper boxes inside.

From the outside, it can't be a glasses case, right?

He unzipped the box.

As expected, there are glasses inside, and the orange-red lenses seem to be made of special materials.

"As expected, I shouldn't expect anything." Xu Qiu thought to himself.

"Isn't it a surprise?" Chen Wanqing smiled and said, "This is goggles. We will use high-power lasers later. Wearing them can protect your eyes from being burned."

Xu Qiu forced a smile to respond.

After the two put on the goggles, they came to the instrument. Chen Wanqing introduced:

"This instrument is mainly composed of three parts, laser light source, signal generator, and oscilloscope. Because there is no computer, a USB flash drive needs to be inserted in advance, and the data will be automatically stored in the USB flash drive.

The test method is very simple, first put the sample into the sample holder, then connect the sample holder to the signal generator and oscilloscope, after setting the parameters, start the laser and the signal generator, the oscilloscope will display the waveform of the current changing with time.

The first test method is the linear boost carrier transient method, or CELIV.

The principle is to give the device a short laser pulse first, the effective layer absorbs the light energy of the laser, generates carriers inside, and then uses a linearly increasing voltage to 'sweep' the electrons and holes to the negative and positive electrodes respectively. A current is formed.

In this method, the current magnitude of the waveform is not important, because what we care about is the charge mobility, so we mainly examine the time when the current signal generates a peak value.

The shorter the time, the faster the carriers move and the higher the mobility.

In the calculation formula, the mobility is proportional to the negative square of time.

The mobility obtained by this method cannot distinguish between electrons and holes, and is their overall mobility.

The other is the time-of-flight method, TOF.

Using this method requires the preparation of special battery devices. First, the effective layer should be relatively thick, usually above 300 nanometers, to ensure that the time for carriers to 'fly' in the effective layer is long enough.

In addition, a blocking layer for electrons and holes needs to be added to the device structure. It can be understood literally that a blocking layer is a material through which electrons and holes can hardly pass.

Usually, an insulator can be used as a barrier layer. We generally use lithium fluoride, and evaporation with a thickness of 5 nanometers can effectively block the passage of electrons and holes.

The principle is similar to CELIV, but it uses a constant voltage, and mainly examines the time when the current signal begins to decay.

Because of the existence of the blocking layer, electrons and holes can be tested separately, and the respective mobility of the two kinds of carriers.

We don't have a device that can be used to test TOF now, so we only test CELIV today. "

The parameters of the instrument are all set by default, and the operation is not difficult. After Chen Wanqing demonstrated, Xu Qiu also tested the other five sets of systems.