With the continuous development of the industrialization process, humans have an increasing demand for traditional fossil resources (oil, coal, natural gas, etc.). As a result, its mining has intensified, reserves have fallen sharply, and mining has become more difficult. The pollutants generated during the use of fossil energy have also made environmental pollution problems intensified. In order to solve energy and environmental problems, non-polluting, inexhaustible, and inexhaustible new energy sources have become people's new demands, such as wind energy, solar energy, water potential energy, geothermal energy, tidal energy, biomass energy, etc. As the source of all the energy of the earth, solar energy has received more and more attention. Solar cells are devices that directly convert light energy into electrical energy through photoelectric or photochemical effects, and then the electrical energy can be converted into thermal energy, light energy and other forms for utilization, so as to realize the full use of solar energy. Therefore, solar cell materials are the most important way to use solar energy. According to the different types and states of materials, solar cells mainly include the following types: crystalline silicon solar cells, thin film solar cells, organic solar cells, dye-sensitized solar cells, perovskite solar cells, and quantum dot solar cells. The semiconductor p-n junction in the solar cell generates a photoelectromotive force effect to directly convert solar energy into electrical energy. It can be seen that the most important and critical component of solar cells is semiconductor materials. The pros and cons of semiconductor materials are closely related to the conversion efficiency of solar cells.
Figure 1. Common solar cell classification
- Converting solar energy into heat energy: The conversion of solar energy into thermal energy is the most widely used and most advanced technology in the utilization of solar energy. The cost of solar energy is relatively low and it is quite economical in terms of energy efficiency. In this respect, it is generally divided into utilization under low temperature, medium temperature and high temperature. The more common one is solar water heaters, which are installed on the roofs of households, which can be used for a long time with a one-time investment, and the hot water generation efficiency is high. In addition, light energy can also be used to make refrigerators and be used in industrial fields.
- Converting solar energy into light energy: Nearly half of the energy irradiated by the sun on the earth is reflected by the clouds, and some is absorbed by the earth, and the rest is reflected by the earth. If this part of the energy reflected by the area can be effectively used, it is a considerable amount of energy. The invention of solar cells enables this part of energy to be used effectively. The use of batteries can be divided into solar cells and solar power stations according to their scale. Solar cells can be used in daily life and can supplement the electricity consumption of residents. Solar power stations are relatively large in scale and can provide electricity for a certain area.
- Converting solar energy into other energy: Solar energy can be used as the energy power of automobiles. With efficient energy absorption and conversion devices, solar energy can be continuously converted into mechanical energy of automobiles, and part of the energy can be stored for use.
- Crystalline silicon solar cells: Solar cells prepared with crystalline silicon materials as the main material, including monocrystalline silicon solar cells and polycrystalline silicon solar cells. The battery materials generally include silicon substrates, metal electrodes, transition metal oxides, and dielectric layers.
- Thin film solar cell: The cell refers to a solar cell made of elemental element thin film, inorganic compound thin film or organic material thin film. The battery is generally prepared with silicon materials, semiconductor materials, nano materials, metal sulfides, etc. as raw materials.
- Organic solar cells: Organic solar cell structures are divided into single-layer Schottky structure, double-layer heterojunction structure, bulk heterojunction structure, laminated structure and PIN structure. The core materials are organic semiconductor materials, such as thiazoles, thiophenes, polycyclic aromatic hydrocarbons, pyridines, pyrazoles, fullerenes, etc.
- Dye-sensitized solar cells: The battery usually consists of a nanocrystalline TiO2 photoanode with dye adsorption, an electrolyte containing an I-3/I-redox couple, and a counter electrode.
- Perovskite solar cells: The battery is composed of perovskite-type metal compounds, conductive glass electrodes, metal electrodes and other materials with a crystal structure of ABX3 type (A represents organic cations, B represents metal cations, and X represents halogen anions).
- Quantum dot solar cells: Quantum dot solar cells usually adopt a "planar" heterojunction structure, that is, metal oxide (such as TiO2, ZnO, etc.) films act as n-type semiconductors and window layers, and quantum dot films act as p-type semiconductors and light absorption layer.
- Dongling Ma. Solar Energy and Solar Cells [J]. Nanomaterials 2021, 11(10), 2682, 653.