1. Silicon solar cells
Silicon solar cells are classified into three types: monocrystalline silicon solar cells, polycrystalline silicon thin-film solar cells, and amorphous silicon thin-film solar cells.
(1) Monocrystalline silicon solar cells
Currently, the photoelectric conversion efficiency of monocrystalline silicon solar cells is approximately 15%, with a maximum of 24%. This is the highest photoelectric conversion efficiency among all types of solar cells. The technology is also the most mature, but its high production cost has prevented its widespread adoption. Because monocrystalline silicon is typically encapsulated in tempered glass and waterproof resin, it is durable and has a lifespan of 15 to 25 years.
(2) Polycrystalline silicon solar cells
The manufacturing process of polycrystalline silicon solar cells is similar to that of monocrystalline silicon solar cells, but the photoelectric conversion efficiency of polycrystalline silicon solar cells is much lower. The photoelectric conversion efficiency of polycrystalline silicon solar cells is approximately 12% (as of July 1, 2004, Sharp Corporation of Japan achieved an efficiency of 14.8%, which is the world's most efficient polycrystalline silicon solar cell). In terms of production cost, it is cheaper than monocrystalline silicon solar cells, the materials are simpler to manufacture, and it saves power consumption, resulting in a lower overall production cost, and therefore it has been widely developed. In addition, the lifespan of polycrystalline silicon solar cells is shorter than that of monocrystalline silicon solar cells.
(3) Amorphous thin-film solar cells
The manufacturing method of amorphous silicon thin-film solar cells is completely different from that of monocrystalline and polycrystalline silicon solar cells. The process is greatly simplified, silicon material consumption is low, power consumption is low, cost is low, conversion efficiency is high, and mass production is convenient. Its main advantage is that it can generate electricity even under low light conditions, showing great potential. However, the main problem with amorphous silicon solar cells is their low photoelectric conversion efficiency. The current international advanced level is around 10%, which is not yet stable. Over time, its conversion efficiency decreases, directly affecting its practical applications.
2. Multi-compound thin-film solar cells
The multi-compound thin-film solar cell material is an inorganic salt, mainly including gallium arsenide III-V group compounds, cadmium sulfide, cadmium sulfide and copper indium selenide thin-film cells.
3. Polymer multilayer modified electrode type solar cells
Replacing inorganic materials in solar cells with polymers is a newly emerging research direction in solar cell manufacturing. The principle involves using the different redox potentials of different redox polymers to create multilayer composites on the surface of conductive materials (electrodes), forming a unidirectional conductive device similar to an inorganic PN junction. In one electrode, the inner layer is modified with a polymer with a lower reduction potential, while the outer layer has a higher reduction potential, allowing electrons to transfer only from the inner to the outer layer. The other electrode is modified in the opposite way; the reduction potentials of the two polymers on each electrode of the first electrode are higher than those of the latter two. When the two modified electrodes are placed in an electrolytic wave containing a photosensitizer, electrons generated after the photosensitizer absorbs light are transferred to the electrode with the lower reduction potential. Electrons accumulated on the electrode with the lower reduction potential cannot transfer to the outer polymer; they can only return to the electrolytic state through the electrode with the higher reduction potential via the external circuit. Therefore, a photocurrent is generated in the external circuit.
4. Nanocrystalline chemical solar cells
Among solar cells, silicon-based solar cells are undoubtedly the most mature, but due to their high cost, they are far from meeting the requirements for large-scale promotion and application. Therefore, people have been constantly exploring technologies, new materials, and cell thinning techniques. Among them, the newly developed nano-TiO2 crystal chemical solar cell has attracted the attention of scientists at home and abroad. Since Professor Gratzel of Switzerland successfully developed the nano-TiO2 chemical solar cell, some domestic institutions have also been conducting research in this field. Nanocrystalline chemical solar cells (NPC cells) are formed by modifying a semiconductor material in its narrow bandgap and assembling it on another large bandgap semiconductor material. The narrow bandgap semiconductor material uses organic compounds, such as transition metals Ru and Os. The sensitizing dye and the large bandgap semiconductor material are nano-polycrystalline TiO2, which are then used to make the electrodes. In addition, NPC cells also use a suitable redox electrolyte.
