This chapter introduces what is solar energy and photovoltaic cell.
1.1 What is solar energy?
Solar energy is energy from celestial bodies outside the earth (mainly the sun). In the interior of the sun, nuclear fusion reactions are continuously taking place, releasing huge amounts of energy and continuously radiating energy into the outer space. The earth we are on is a planet in the solar system, and nature is absorbing the energy radiated by the sun at all times. Broadly speaking, in addition to light energy and heat energy, the potential energy of wind, chemical, tidal, wave, and water on the earth all come from solar energy.
Solar energy is a clean, non-polluting, non-exhaustible, free, and non-returnable energy source. The use of solar energy by mankind is mainly concentrated in two aspects: thermal energy utilization and power generation.
According to the current technology, there are two methods of solar power generation: one is to use the water vapor generated by thermal energy to drive a generator to generate electricity, referred to as thermal power generation (see Figure 1-1); the other is to generate electricity by photovoltaic cell.
1.2 What is a photovoltaic cell?
Photovoltaic cell is the abbreviation of solar photovoltaic cell, also known as photovoltaic cell or solar cell. It is a kind of semiconductor device similar to crystal diode. It is a device that converts sunlight energy into electrical energy through the photoelectric effect. As long as the photovoltaic cell is exposed to light, it can output voltage and current instantly (see Figure 1-2). This phenomenon is called photovoltaic effect in physics, or photovoltaic for short.
The history of photovoltaic cell can be traced back to the 19th century. In 1839, the photovoltaic effect was first discovered by the French physicist A.E. Bec-qurel.
In 1883, the first photovoltaic cell was successfully prepared by Charles Fritts. Charles uses a very thin gold layer on the storage semiconductor to form a semiconductor metal junction, and the device has an efficiency of only 1%.
In 1946, Russell Ohl applied for a patent for the manufacture of modern photovoltaic cell.
In 1954, the first practical single-product silicon photovoltaic cell was born in Bell Labs in the United States, with a photoelectric conversion efficiency of 6%.
Since 1960, the artificial satellites launched by the United States have used photovoltaic cell as a source of energy.
During the energy crisis in 1970, countries around the world realized the importance of energy development. In 1973, the oil crisis occurred, and people began to transfer the application of photovoltaic cell to general people’s livelihood purposes.
In the United States, Japan, Israel and other countries, a large number of solar energy devices have been used, and the goal of commercialization has been advanced. Among these countries, the United States established the world’s largest solar power plant in California in 1983, which can generate up to 16 megawatts. South Africa, Botswana, Namibia and other countries in southern Africa have also set up special projects to encourage remote rural areas to install low-cost photovoltaic cell power generation systems.
In China, the solar power generation industry is also strongly encouraged and funded by the government. In March 2009, the Ministry of Finance announced that it intends to subsidize large-scale solar projects such as solar photovoltaic buildings. Since then, photovoltaic cells have sprung up like bamboo shoots after the rain, and they have developed vigorously on the land of China. In just a few years, China has become a major country in photovoltaic cell production.
In recent years, solar photovoltaic technology has made significant progress, and more than 100 photovoltaic cells have been successfully developed, but the most are photovoltaic cells produced using silicon crystal materials, accounting for more than 90% of the total photovoltaic cells. In recent years, the photoelectric conversion efficiency of photovoltaic cells has also made a big breakthrough, generally above 13%, and the high can reach 20%.