Organic solar cell (OPV) is a solar cell whose absorber layer is an organic semiconductor (polymer or small molecule). The preparation of organic semiconductor materials requires the use of highly conjugated organic materials. The conjugation of organic molecules results in the delocalization of the electrons associated with the double bond over the entire conjugation length. These electrons have higher energy than other electrons in the molecule, and can impart conductive or semi-conductive properties to organic materials. The working process of OPV includes four aspects: light absorption, exciton diffusion, exciton dissociation, and charge transport and collection. When the energy of the incident light is greater than the energy gap, the donor molecules are excited and the electrons transition from the HOMO orbital to the LUMO orbital, thereby forming a hole in the HOMO orbital. When holes and electrons bind to each other to form electron-hole pairs, excitons are formed. The excitons are diffused and dissociated to obtain free electric charges, and the photocurrent is collected in the active layer to complete the photoelectric conversion. The specific advantages of OPV are as follows: (1) Great chemical variability and a wide range of sources of raw materials; (2) It can change and improve the material's spectral absorption capacity, expand the spectral absorption range, and improve the carrier's transport capacity through a variety of ways; ( 3) It is easy to process and can be processed in a large area; (4) It is easy to carry out physical modification; (5) The battery production can be diversified; (6) The cost is low. OPV has the advantages of low manufacturing cost, wide material sources, simple preparation process, light weight, flexibility, ultra-thin, transparent and other advantages. It is convenient for transportation and flexible deployment, and is of great significance for large-scale use of solar energy to provide cheap electricity. The flexibility and light weight of organic solar cells have greatly broadened the application range and environmental compatibility of solar cells, and the installation and use of solar cells can be gradually expanded from fixed plane installation to more flexible curved installation mode, which is conducive to the realization of portable applications and is widely used in building integration and other fields.
Figure 1. OPV working mechanism