I Have a Research Support System

"Next, let's check the results of our junior." Chen Wanqing said.

"Senior, don't worry, you'll be fine." Xu Qiu was full of confidence.

"Okay, then I'll wait and see," Chen Wanqing said, "I'll teach you how to test first."

Following the guidance of the senior sister, Xu Qiu looked at a set of instruments on the right side of the evaporation machine.

A computer, a box with a digital display panel, a component integrating eight probes, and a black cover;

The most conspicuous one is a searchlight-shaped hemisphere embedded in the bottom of the glove box, and the nameplate next to it is marked "Sol3A Class AAA Solar Simulator, 94043A Solar Simulator".

Chen Wanqing was not in a hurry to introduce the instrument, but started from the principle:

"The testing process, in simple terms, is to irradiate the battery device with simulated sunlight.

During this period, a linear voltage sweep is used to obtain the curve of the current density changing with the voltage, that is, the J-V characteristic curve.

Through the J-V characteristic curve, the short-circuit current density Jsc, open-circuit voltage Voc and fill factor FF of the device can be calculated.

In addition, there is also the input power density. We are simulating the AM1.5G condition, that is, the average illuminance of sunlight incident on the surface, and the specific value is 100 milliwatts per square centimeter.

Finally, the photoelectric conversion efficiency (PCE) of the device is equal to Jsc*Voc*FF/input power density through the formula. "

Xu Qiu has seen these physical quantities in the review before, so he is no stranger to them, but this is the first time he has seen the simulated light source.

He wondered: "How do you know this light source, it simulates exactly the intensity of a sun's light?"

"At the beginning of use, the standard silicon battery was used to calibrate its light intensity," Chen Wanqing explained: "However, after a long time of use, the light intensity will decline, so every once in a while, it needs to be re-calibrated, otherwise the test results will be lower.”

Chen Wanqing continued: "It has two switches, one is the master switch and the other is the light control switch.

Turn the main switch, that is, the red button from 0 to 1, and let it warm up first. It usually takes ten minutes to warm up. During this time, I can introduce other components to you. "

Xu Qiu turned on the main switch, and there was a "whoosh" sound from inside the instrument, as if a fan was running.

"Senior sister, do you want to turn on the computer?"

"Yes."

Xu Qiu entered the glove box and pressed the power button of the computer.

The familiar XP system startup screen is loading.

After waiting for more than ten seconds, the computer desktop with blue sky and white clouds appeared.

But the above is clean, except for "My Computer", there is only one software, the name is "Madou Comprehensive University Physics Laboratory".

"Is it this software?" Xu Qiu moved the mouse over.

"Yes, Teacher Wei asked for this from the Department of Physics, and they programmed it with LabVIEW." Chen Wanqing said.

Xu Qiu opened the software and found that the interface of the software was very simple without any bells and whistles.

The upper left is the parameter setting area, the lower left is the image display area, there are two coordinate axes, horizontal and vertical, the horizontal axis is voltage, the unit is volts, and the vertical axis is current density, the unit is ampere per square centimeter;

The upper right is the test result display area, including Jsc, Voc, FF, and PCE, and the lower right is the dark state compensation, start, and stop buttons.

The parameters have default values, which are basically set.

The initial scanning voltage is -1 volt, the maximum voltage is 1 volt, the scanning interval is 0.01 volts, the battery area is 0.09 square centimeters, the dark state compensation is 0, and the current test condition is dark state.

After getting familiar with the software interface, Xu Qiu looked at the box with the digital display panel next to the computer and asked:

"Sister, what is this? Is it used to test the current?"

"It's very smart," Chen Wanqing said, "This is a Keithley 2400 source meter, it can provide a highly stable DC voltage, and the current test passed in real time has a voltage accuracy of 1 picoamp, which is ten minus 12 times. Fang Ampere."

Xu Qiu pressed the start button of the source meter, and after a beep, the instrument started, and the two digital display panels lighted up, showing current and voltage respectively.

He then proceeded to install the substrate.

First take a zinc oxide substrate marked "1:1:0, 1200r", place the back of the substrate, that is, the glass side down, on the upper platform of the sun simulation light source.

There is a groove on the platform, the substrate can just be stuck in, and it is directly above the hemispherical surface of the simulated light source.

After the light source is turned on, the light can pass through the glass and irradiate the active layer vertically, where photoelectric conversion occurs and photocurrent is generated.

Next, he took the component with the eight probes and connected it with a bracket, with the probes facing down, pressing it on top of the substrate.

There are two sets of wires connected to the outside of the component. Each set of wires is black and red, and there are four wires in total. They are connected to the Keithley source meter in the "four-wire method".

The eight probes are parallel to each other, three on the left and one on the left and one on the top and bottom.

These probes fit just right on the edge of the battery device.

Among them, the left and right six probes are just attached to the ends of the six sets of aluminum electrodes of the device, while the upper and lower probes are attached to the ITO electrodes.

In fact, the ITO electrodes of the six batteries are shared, and only one probe is needed, but for the sake of beauty and preventing accidental breakage of the probes, two electrodes are designed.

Finally, Xu Qiu used a black cover to cover the solar simulation light source together with the substrate and probe components.

"Okay, it's time to prepare for the test," Chen Wanqing said: "There are two types of tests, light and dark. Generally, you need to test the dark state first, and then continue to test under the light."

"Because in the dark state, the battery device will also generate a small amount of current, which is not generated by light, so it needs to be deducted.

Although in general, even without deducting, the impact on the result is not great, but in order to ensure the rigor of the result, this step cannot be omitted. "

"Okay." Xu Qiu clicked the start button of the software.

"drop."

The source meter starts to work, and the voltage value on the left starts from -1 volt at an interval of 0.01 volts, and keeps jumping and increasing;

The current on the right is initially negative, and only at the microampere level. After the voltage reaches 0.64 volts, it turns positive and increases rapidly.

The scan ends and the results are obtained.

In the dark state, the short-circuit current density is only -0.0018 mA per square centimeter, and the photoelectric conversion efficiency is 0.0033%.

After Xu Qiu clicks Dark State Compensation, the dark state compensation in the upper left corner automatically changes to -0.0033%.

Seeing that the short-circuit current density is a negative value, he wondered: "Senior sister, why is this Jsc a negative value? The literature is all positive."

"This is caused by the test method. We provide the battery with a reverse bias voltage to offset the photo-generated current it generates, so the measured current is a negative value, which means that the direction of the current is opposite to the direction of the voltage. And in the battery When the device is actually working, it is the right time." Chen Wanqing said.

Xu Qiu nodded thoughtfully.

Then, he changed the test condition of the software to the bright state, and turned on the light control switch of the simulated light source.

There was a "pop", and a ray of light appeared from the bottom of the black cover.

Xu Qiu clicked the start button, and after voltage scanning, the bright state J-V characteristic curve was obtained.

On the right side of the software interface, four photoelectric parameters are displayed, the short-circuit current density is -11.02 mA per square centimeter, the open-circuit voltage is 0.65 volts, the fill factor is 0.60, and the photoelectric conversion efficiency is 4.30%.

"Student, it's amazing!" Seeing the results of the experiment, Chen Wanqing said a little excitedly, "It's the first time I made a device and I succeeded."