Solar cell materials

There are many kinds of materials for solar cells, including amorphous silicon, polycrystalline silicon, CdTe, CuInxGa (1-x) Se2 and other semiconductors, or elements of three, five and six groups linked together. In short, the materials that generate electricity after illumination are the materials that solar cells look for.
The electric vehicle solar charging station mainly tests the reaction and absorption of light through different manufacturing processes and methods to achieve a revolutionary breakthrough of combining broad energy gap and allowing full absorption of short or long wavelength, so as to reduce the cost of materials.
There are also types of solar cells: substrate type or thin film type. The substrate can be split into single crystal type or cooled into polycrystalline blocks after dissolution. The thin film type can be better combined with the building. If there is curvature or flexible type or folded type, the material is usually amorphous silicon. There is also a kind of organic or nano material research and development, which is still prospective research and development. Therefore, we have heard about different generations of solar cells: the first generation of substrate silicon based, the second generation of thin film, the third generation of new concept research and development, and the fourth generation of composite film materials.
The first generation of solar cells has the longest development and the most mature technology. It can be divided into monocrystalline silicon, polycrystalline silicon and amorphous silicon. In terms of application, monocrystalline silicon and polycrystalline silicon were the bulk.
The second generation thin film solar cells are manufactured by thin film process. The species can be divided into Cadmium Telluride CdTe, Copper Indium Selenide CIS, Copper Indium Gallium Selenide CIGS, Gallium Arsenide GaAs
The biggest difference between the third generation battery and the previous generation battery is the introduction of organic matter and nanotechnology in the manufacturing process. There are photochemical solar cells, dye photosensitive solar cells, polymer solar cells, and nanocrystalline solar cells.
The fourth generation is to make multi-layer structure for the thin film that absorbs light from the battery.
Some battery manufacturing technology. Not only one type of battery can be manufactured. For example, in the process of polysilicon, both the type of silicon crystal plate and the type of thin film can be manufactured.
Common polymer solar cell materials include polyvinylcarbazole (PVK), polyacetylene (PA), poly-phenylene vinylene (PPV) and polythiophene (PTh).
(1) Polyvinyl carbazole (PVK)
Among the polymers with photoelectric activity, PVK is the earliest discovered and most fully studied. Its side group has a large electronic conjugation system, which can absorb ultraviolet light. The excited electrons can migrate freely through the charge complex formed by the adjacent carbazole ring. They are usually doped with I2, SbCl3, trinitrofluorenone (TNF), and nitrostilbenebenzene derivative tetracyanoquinone (TCNQ).
(2) Polyacetylene (PA)
PA is the electronic polymer with the highest conductivity measured so far. Its polymerization methods mainly include Shirakawa Yingshu method, Namm method, Durham method and rare earth catalytic system. Yingshu Shirakawa uses Ziegler-Natta catalyst with high concentration, namely TiOBu4-A1Et3, to directly prepare self-supported polyacetylene film with metallic luster from gas-phase acetylene; The film is formed on the oriented liquid crystal substrate, and the PA film is also highly oriented. The characteristic of the Narrman method is that the polymerization catalyst is "aged at high temperature", so the mechanical properties and stability of the polymer are significantly improved.
(3) Polyphenylene vinylene (PPV)
In recent years, PPV materials are the most widely used in the field of optoelectronics and have the highest device efficiency. Due to its conjugated structure, the molecular chain is very rigid, often difficult to melt and dissolve, and difficult to process. The method to obtain soluble PPV is to introduce at least one long-chain alkane into the benzene ring. The number of alkanes shall be at least 6. It is also found that the solubility of straight alkanes with branched substituents is better than that of straight alkanes with the same carbon number. The representative material is MEH-PPV (MEH; 2-methoxy-5 (2 '- ethylhexoxy)), which has good solubility and is convenient to use; The forbidden band width is 2.1eV, which is relatively moderate.
(4) Polythiophene (PT) derivatives
Among all conjugated polymers, polythiophene is a very good photovoltaic material. Because of its suitable band gap and high hole mobility, it has become one of the research hotspots of organic photovoltaic materials in recent years. Among them, the photovoltaic devices with the blend film of regionally structured poly (3-hexyl) thiophene (P3HT) and soluble C60 derivative PCBM as the active layer have the highest energy conversion efficiency under heat treatment, and the energy conversion efficiency has reached about 5%. Therefore, the design and synthesis of new polythiophene derivatives, the study of the relationship between the structure and properties of polythiophene, and the improvement of the properties of polythiophene derivatives through structural modification have attracted the attention of researchers. From the perspective of photovoltaic materials, these polythiophene derivatives should have the most basic properties: good solubility and film formation, wide absorption spectrum (especially in the visible light region) and high carrier mobility.