Organic solar cell can convert solar energy to electric energy. Based on the photovoltaic effect, organic solar cell materials can absorb photons under the irradiation of the sun. When the energy of the photon is stronger than the band gap width of organic materials, excitons will be generated, but the excitons will not dissociate automatically. When two materials with different electron affinity energies and ionization potentials contact, a contact potential difference is generated at the contact interface, which may cause excitons to dissociate. The firstly reported organic solar cell was in 1959, but the conversion efficiency is very low, only 2*10-6. Therefore, many research works focus on improving the conversion efficiency of organic solar cell (OPV) materials.
Organic solar cell (OPV) materials have the advantages of low synthesis cost, tunable structure, good flexibility and film-forming properties. The process of manufacturing organic solar cells is simple, and can be operated at low temperature, which can reduce the cost. Therefore, organic solar cell (OPV) materials are ideal candidates for portable devices, flexible systems and solar home systems.
- Portable devices: With the quickening pace of people's life and work, portable devices such as sports watch and pocket calculator have become popular, and organic solar cell materials can meet the demands.
- Flexible systems: Organic solar materials can use flexible substrates, so it is expected to be applied in the field of flexibility.
- Solar home systems: Solar home systems are designed to develop nature energy and alleviate environmental pollution. Organic solar cell (OPV) materials are ideal composition for solar home systems.
There are a wide variety of materials for organic solar cell (OPV) material, which can be divided into the following types.
- Organic small molecular solar cell materials: The organic small molecule solar cell materials have certain planar structures and can form self-assembled polycrystalline films. Such ordered molecular thin films greatly improved the mobility of organic solar cell materials. The generally organic small molecule solar cell materials are pentacene, phthalocyanines, subphthalocyanines, cyanines, porphrins, perylene bisimides and C60.
Figure 1 The molecular structures of organic small molecular solar cell materials.
- Organic macromolecular solar cell materials: Since the 1990s, Organic macromolecular solar cell materials have developed rapidly. Organic macromolecular solar cell materials include fullerene derivative, poly (p-phenylethylene) and its derivatives, polythiophene and its derivatives, nitrogen-containing conjugated polymers and polyfluorene and its derivatives.
Figure 2 Some examples of organic macromolecular solar cell materials.
- D-A system organic solar cell materials: A material that covalently connects the donor and the acceptor to form D-A system. The application of these materials in devices is expected to improve device efficiency, which is the focus of current research.
Figure 3 Some examples of D-A system solar cell materials.
- Organo-inorganic hybrid system: Organic and inorganic materials are combined to form a hybrid system. Due to the synergistic effect, the materials obtained have the advantages of both.
Figure 4 An example of organic-inorganic hybrid materials.
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