I Have a Research Support System

Afternoon, laboratory.

As soon as she saw Xu Qiu, Chen Wanqing took the initiative to say: "My junior is here, today I will teach you the operation of spin coating."

"Okay." Xu Qiu replied.

He thought to himself that he usually took the initiative to ask the senior sister for advice. Why is the senior sister so enthusiastic today, but he didn't care too much.

After chatting for a while, the two put on their lab coats and started working.

[Spin-coating skill detected, is it recorded? 】

"Record."

"System, if you encounter skills related to experiments later, can you automatically record them?"

【Can. 】

…………

"The main instrument used in the spin coating operation is the coater.

First, drop the solution on the substrate, and then use the glue homogenizer to rotate the substrate at high speed. Under the action of centrifugal force, the solution is quickly thrown away, the solvent in the solution evaporates, and finally a uniform solid film is formed.

Usually, the thickness of the thin film prepared by spin coating method is between several nanometers and hundreds of nanometers.

Our laboratory now has two homogenizers, one inside the glove box and one outside the glove box.

Today I will teach you the spin coating method of three solutions, which are PEDOT, zinc oxide and effective layer solution.

PEDOT first, be careful when spin coating..."

After the introduction, Chen Wanqing said, "That's the principle and method of operation. Do you have any questions?"

"No problem, I understand." Xu Qiu said.

"Okay...then I'll go back. This afternoon should only be enough to finish applying PEDOT and zinc oxide. Let's talk about the effective layer on Sunday." Chen Wanqing said.

"Yeah." Xu Qiu nodded.

He felt that the senior was a little strange, what happened to her today?

Forget it, don't think about it, it's important to do experiments.

…………

By reading the literature in the past few days, Xu Qiu has a general understanding of the structure of organic solar cell devices.

Usually divided into normal structure and inverted structure.

The normal structure is glass as the substrate, the ITO on it as the positive electrode material, and then the hole transport layer and the effective layer are prepared by spin coating, and finally the electron transport layer and the negative electrode material are prepared by vacuum coating (evaporation).

In the inverted structure, the first is the glass substrate, ITO is the negative electrode material, and then the electron transport layer and the effective layer are prepared by the spin coating method, and finally the hole transport layer and the positive electrode material are prepared by the evaporation method.

Cleaning substrates, preparing solutions, spin coating, and vacuum coating are the four major skills for preparing organic solar cells. After learning spin coating today, only evaporation is left.

Xu Qiu turned on the auxiliary system to carry out experimental operations.

The first is the preparation of PEDOT film.

PEDOT is a water-soluble polymer material with high electrical conductivity. In order to increase its solubility, it is usually necessary to add a certain proportion of polystyrene sulfonate (PSS), so strictly speaking, it is called PEDOT: PSS is more suitable.

Xu Qiu first dried 24 substrates with a nitrogen gun and put them into two Petri dishes.

Then the petri dish with the lid removed was put into an ozone generator and treated for 30 minutes.

Ozone is difficult to store, and an ozone generator can convert oxygen in the air into ozone.

Treating the substrate with ozone can increase the wettability of its surface, so that the liquid can easily stay on the substrate during the spin coating process, and avoid obtaining a film with holes.

Taking advantage of the interval of ozone treatment, Xu Qiu took out the reagent bottle containing PEDOT aqueous solution from the refrigerator, sucked up about 2ml of the solution with a disposable dropper, and transferred it to a 4ml centrifuge tube.

Then take out a 1 ml disposable syringe, remove the needle and soak up the solution, and install a 0.22 micron water phase filter on the head of the syringe.

...

"What is the taste."

Xu Qiu suddenly smelled a faint fishy smell.

He quickly realized that the ozone should be leaking.

Because the toxicity of ozone is relatively low, he didn't wear a special gas mask, but took a deep breath and walked to the ozone generator.

Stop the instrument first, and then start the inspection.

The door of the instrument was tightly closed, and the rubber hose at the back of the instrument was also connected to the outside of the window.

Everything looks fine, so how did the smell come out?

Is it there?

With a deduction in Xu Qiu's mind, he found the toolbox, took out a roll of 3M black electrical tape, and took the tape back to the ozone generator.

At this time, the smell of ozone has almost dissipated.

He went around the hose at the back of the instrument and inspected it carefully section by section.

Sure enough, there was a crack in the rubber hose due to aging, and judging from the crack marks, it should have just broken.

Xu Qiu glued the cracks with adhesive tape.

Turn on the instrument again, this time there is no smell of ozone.

However, sticking with adhesive tape is only a stopgap measure, and the best way is to replace a new rubber tube.

So Xu Qiu shouted:

"Sister, the hose of the ozone generator is cracked. I'm sticking it with tape now, and I need to get a new hose later."

"Okay, I'll write it down." Chen Wanqing said.

After solving this little trouble, Xu Qiu continued the experiment after the countdown of the ozone generator was over.

He took the petri dish out of the instrument, picked up a substrate with tweezers, and placed the substrate on the platform of the gel coater.

There is a small hole under the platform, which is connected to a vacuum pump to ensure that the substrate does not move during high-speed rotation.

He set the parameters of the homogenizer, the speed is 3000 rpm, and the rotation time is set to 60 seconds.

Then use a syringe to squeeze out about 0.1 ml of PEDOT solution to the center of the substrate, and then use the end of the filter to drag the liquid surface so that the solution covers the entire substrate.

Then press the start button, the glue homogenizer will automatically turn on the vacuum pump, and run according to the preset parameters. After the platform stops completely, it will automatically turn off the vacuum pump.

Another fool-proof machine similar to an ultrasonic cleaner.

Xu Qiu picked up the spin-coated substrate with tweezers and carefully inspected it. He found that the spin coating was perfect. The blue-purple film covered the entire substrate, and the surface of the film was smooth without holes.

Put the substrate back into the original Petri dish, and continue to clamp the next piece.

After repeating the spin coating 12 times, 11 pieces were perfect, and only one piece was slightly flawed, and only three-quarters of the area was coated.

Xu Qiu threw the flawed piece into the old substrate box.

Next, is the thermal annealing step.

For the PEDOT:PSS film, the main function of annealing is to remove the residual moisture, so it only needs to be slightly higher than the boiling point of water.

Xu Qiu put the spin-coated substrate together with the petri dish on the heating platform with a set temperature of 130 degrees Celsius, and then pressed the stopwatch to start timing.

It usually takes more than 30 minutes.

After waiting for a long time, Xu Qiu returned to his desk, intending to drink some water and rest for a while.

Suddenly, the senior sister next to her suddenly asked, "Xu Qiu, what are your plans for the future?"

Xu Qiu almost spit out the water that was in his mouth.