Space solar cells: a new dawn of energy for aerospace

In the vast and boundless journey of space exploration, energy supply has always been a key factor determining the performance of spacecraft and the success or failure of missions. Space solar cells, as the core power supply equipment in the aerospace field, use sunlight as "fuel" to continuously inject power into spacecraft. Their efficiency performance profoundly affects the pace of human progress towards the universe.

The working principle of space solar cells is based on the photoelectric effect. When photons in sunlight collide with the surface of a battery made of semiconductor materials, the energy of the photons is absorbed, causing the electrons inside the semiconductor to gain enough energy to break free from atomic constraints and form a directed flow of electrons, thereby generating electrical energy. This seemingly simple process of energy conversion faces many challenges in the complex and ever-changing environment of space.

From the application examples, many spacecraft have achieved long-term stable operation with the help of solar cells. For example, the International Space Station is equipped with a large and advanced array of solar cells. The multi junction gallium arsenide solar cell used has a conversion efficiency of about 30%. These huge "wings" have an area of several hundred square meters and can provide several megawatt hours of electricity to the space station every year, maintaining the normal operation of various complex scientific research equipment, life support systems, and communication facilities inside the station. According to statistics, about 90% of the daily electricity supply of the International Space Station relies on solar cells, greatly reducing its dependence on traditional energy sources such as disposable chemical batteries. This enables the space station to operate continuously in orbit for decades, laying a solid foundation for long-term space research work.

Looking at the Mars probe again, taking China's Tianwen-1 as an example, its three junction gallium arsenide solar cell array is designed specifically to adapt to the Martian environment. Mars is further away from the Sun, with only about 43% of the light intensity in Earth's orbit, and the presence of a large amount of dust in the Martian atmosphere will further weaken the light. However, the battery array, with its high conversion efficiency and excellent radiation resistance, can still provide stable power to the probe in the complex environment of the Martian surface, supporting it to complete a series of difficult tasks such as orbit, landing, and patrol. During the months long Mars exploration mission of Tianwen-1, solar cells provided continuous and stable power supply, assisting the probe in conducting comprehensive exploration of Mars and obtaining a large amount of valuable scientific data.

In terms of efficiency advantages, space solar cells have significant characteristics compared to other energy sources. Compared to disposable chemical batteries, it eliminates fuel storage limitations and can generate electricity continuously as long as there is light. Taking the chemical batteries used in early satellites as an example, their power is limited and often runs out within weeks or months, while solar cells can theoretically provide continuous power throughout the entire service life of spacecraft. Meanwhile, compared to nuclear energy (such as radioactive isotope thermal power sources), solar cells are safer, more environmentally friendly, have no risk of nuclear leakage, and have relatively mature technology and lower costs.

Of course, space solar cells also have certain limitations. In deep space exploration missions far from the sun, the intensity of light sharply decreases, resulting in a significant decrease in battery output power. For example, near the orbit of Jupiter, the light intensity is only about 4% of that of Earth's orbit, which greatly reduces the power supply efficiency of solar cells and makes it difficult to meet the high-energy consumption needs of spacecraft. In addition, harsh space environmental factors such as space radiation and micrometeoroid impacts can gradually damage the performance of battery materials and reduce conversion efficiency. If a satellite operates in low Earth orbit for a long time, its solar cell surface will be bombarded by high-energy particles, causing the battery performance to decline year by year and affecting the satellite's service life.

To improve the efficiency of space solar cells, researchers are constantly exploring innovative technologies. On the one hand, the development of new semiconductor materials, such as perovskite materials, is expected to achieve a theoretical conversion efficiency of over 40%, and has advantages such as low cost and simple preparation process. Currently, phased results have been achieved in the laboratory; On the other hand, improving the battery structure design by adopting a multi junction stacked structure can enhance the efficiency of light energy utilization by absorbing different wavelengths of sunlight through different materials. For example, a new type of four junction solar cell being developed in the United States is expected to have a conversion efficiency of over 45%.

Space solar cells, with their unique advantages, play an irreplaceable role in existing aerospace missions. Despite facing challenges, their efficiency will continue to improve with the continuous advancement of technology, providing stronger and more sustainable energy support for the grand blueprint of human exploration of the universe, and helping us sail towards more distant stars and oceans.