You promised to build cars, so why did you go into the military industry?

"It's not that I don't believe it, but this thing of yours..." Director Qi Kaifeng took a sip of tea, "If I remember correctly, the Shockley-Quisser limit is a line drawn for the photoelectric conversion efficiency of a single-structure solar photovoltaic panel."

"33.7%?" Gao Jingming's voice trembled slightly. "So, I took a different approach and adopted a layered technology."

"The technology mentioned by Edmund D. Jackson in his 1955 conference paper 'The Direction of Improvement of Semiconductor Solar Converters,' which involves stacking semiconductor PN junctions with different band gaps to improve efficiency?" Director Qi Kaifeng leaned back slightly, looking relaxed. "That makes sense."

Then, Director Qi Kaifeng got up, went to the group of five, pulled up a chair, and sat down.

"Given your patriotism and the recent contributions of comrades Wang Bing and Su Qing, I can make an exception and reveal that we have achieved this efficiency in the laboratory for the three-to-five multi-junction solar photovoltaic panels."

Everyone watched as Director Qi Kaifeng first extended four fingers of his left hand, paused for a moment, and then slowly opened his thumb.

"45?!" Gao Jingming exclaimed in disbelief.

Li Ran, who witnessed this scene, was completely bewildered and had no idea what the two were talking about.

But it seems, perhaps, almost, possibly, that the cooperation with the national aerospace team is going to fall through?

Seeing Li Ran's bewildered look, Gao Jingming, deeply affected, felt somewhat dejected and explained the whole story to Li Ran with a bitter expression.

After the explanation, Li Ran understood that the so-called Shockley-Quyther limit is also called the SQ limit.

Specifically, under standard test conditions (AM1.5 spectrum, light intensity 1000W/m²), a single-junction solar photovoltaic panel with an optimal band gap (approximately 1.34 eV) can convert up to 33.7% of the energy in incident sunlight into electrical energy.

In other words, no matter how much the materials are optimized or the process is improved, the theoretical upper limit of the photoelectric conversion efficiency of a single-layer solar photovoltaic panel is 33.7%!

There are two main reasons why the photoelectric efficiency of single-layer solar photovoltaic panels cannot reach 100%.

First, if the energy of a photon is lower than the "band gap" of a semiconductor material, it will pass directly through the solar photovoltaic panel like air and will not generate an electric current.

Secondly, since the photon energy is higher than the "band gap", the solar photovoltaic panel can only utilize the portion of energy equal to the "band gap", and the excess will be dissipated as heat.

It's like someone going to a fishpond and using a fishing net made of "special material" to catch fish.

Fish smaller than the mesh size will pass right through the mesh, while fish larger than the mesh size can break free. In the end, the person can only catch fish that are stuck in the mesh and are about the same size as the mesh.

However, if the solar photovoltaic panels are transformed from a single-layer structure to a multi-layer structure and stacked together...

For example, if the upper layer uses perovskite solar photovoltaic panels to absorb high-energy blue-violet light, and the lower layer uses crystalline silicon solar photovoltaic panels to absorb low-energy red light that passes through the upper layer, then the theoretical limit of photoelectric conversion efficiency can reach 43%.

That is, the upper layer uses a net with large mesh to catch big fish, and the lower layer uses a net with small mesh to catch small fish.

This way you can catch more fish at once.

Director Qi Kaifeng gestured to the three-to-five multi-junction solar photovoltaic panel, which has a photoelectric conversion efficiency of 45%, meaning that at least three layers of solar photovoltaic panels of different materials are stacked.

In Gao Jingming's words, he had only stacked two layers; stacking three layers was too difficult.

After listening to Gao Jingming's explanation, Li Ran's brain was working frantically. Although he was happy that the country had a more powerful product, he felt that he had overlooked something.

"What did Director Qi just say?" Li Ran stroked his chin, lost in thought. "In the laboratory, the Three-Five Clan..."

Li Ran's eyes lit up, and he slapped his thigh:

"Director Qi, you just said 'in the laboratory,' does that mean it can't be mass-produced yet?"

Director Qi Kaifeng, who had been smiling as he looked at the five-person team from United Industries, paused for a moment:

"Mass production? This thing can actually be mass-produced?"

"!" Hearing Director Qi Kaifeng's question, Gao Jingming felt a glimmer of hope.

Before coming to witness the rocket launch, Gao Jingming had just calculated the cost of his own solar photovoltaic panels and immediately said:

"We've already achieved mass production! Otherwise, we wouldn't be installing it on vehicles! And its overall cost is 3200 yuan per square meter!"

Li Ran then added:

"Our joint industrial manufacturing plant has begun upgrading its power system, with an estimated 40 square meters of solar photovoltaic panels to generate 80 kilowatt-hours of electricity per day."

To clarify, the United Industrial Manufacturing Plant is located in Linjiang County, Jiangyang City, Sichuan Province, where the average daily sunlight level is only half that under standard testing conditions.

After Li Ran finished speaking, Lin Yu, as if thinking of something, asked:

"Director Qi, the photoelectric conversion efficiency we measured in our lab doesn't require 'focused light' conditions to achieve, does it?"

Seeing that Director Qi Kaifeng was clearly frozen in place, Li, Gao, and Lin realized that they had guessed correctly, and they breathed a sigh of relief, knowing that the matter was most likely to succeed.

However, before Gao Jingming could fully relax, Director Qi Kaifeng had already gotten up and walked out:

"What are you standing there for? Take me to unpack the samples! What if these valuable things get stolen if we just leave them in this open parking lot?!"

Upon hearing this, Li Ran became somewhat nervous:

"Huh? There are spies here?"

Director Qi Kaifeng's voice echoed down the corridor:

"What if? Better safe than sorry! Quick!"

In the open-air parking lot of the launch center, a line of soldiers quietly appeared and began to impose martial law.

Soon, a movable fence was erected to enclose the open-air parking lot. Then, to avoid suspicion, the cars parked inside were loaded onto trucks and transported to a nearby military base.

The official explanation given was that "an unknown high-frequency signal was detected, requiring dismantling and inspection."

On the way to the military base with the transport vehicle, Gao Jingming noticed Director Qi Kaifeng's tense expression and reassured him:

"Director Qi, although the raw materials for our product are common elements such as calcium, titanium and silicon, the formula is also very difficult to reverse engineer."

Even if it is reverse engineered, it's useless because without the manufacturing process, it cannot be mass-produced.

Even if it were stolen by a spy, all you'd get would be an expensive toy that only exists in a laboratory.

"Your factory's employees..." Director Qi Kaifeng asked with some concern.

"Don't worry, our CEO Li is a people's entrepreneur! All employees' salaries are at least five times the industry average, and there's no upper limit for those who earn more." Gao Jingming patted his chest confidently. "The loyalty of our employees is absolutely unquestionable."

Noticing that Director Qi Kaifeng's gaze was on him, Li Ran smiled shyly: "They deserve it all."

They drove in silence until they arrived at the military base, and then drove directly into an underground warehouse.

Under the command of Lin Yu and Gao Jingming, the soldiers quickly dismantled the four modified Lingyun SU7 vehicles.

The solar panels on the vehicle were completely removed.

Subsequently, Gao Jingming and Lin Yu worked together to modularize and pack it into boxes.

Soon, a truck drove out of the military base, followed by three identical trucks that silently drove away from the base in batches at intervals, but their destinations were not the same.

Watching the last truck leave, Li Ran clicked his tongue in amazement.

"Director Qi, isn't this a bit over the top?"

"What are you thinking? It's just a normal military training exercise. The equipment is good, but it's not worth making such a fuss about." Director Qi Kaifeng smiled.

"What about just now...?"

"The troops happened to have a field training mission recently, so we lent them some props and a venue, and also to enhance the vigilance of the staff."

The next day, the cars that had been towed back were returned in batches.

Each vehicle showed obvious signs of disassembly, and some were indeed found to have hidden listening devices installed.

One of the cars, a black Volkswagen Santana, was openly mixed in with the others. Its rear seats had been completely removed, and the modularly packaged photovoltaic components were placed inside the vehicle.

After registering, a worker from Factory 627 received the Volkswagen Santana that was rightfully his, and then drove back to Chang'an to visit relatives under the pretext of taking a holiday during the National Day holiday.