A brief introduction about the polymer solar cells

Source: 2020 - 04 - 14 seeing then hits: time introduction of polymer solar cells, the study of polymer solar cells can be traced back to the 1980 s. In 1977, a. j。 Heeger and h. Hirakawa joined the trace amounts of iodine in the polyacetylene, get the material conductivity is 108 times that of the pure polyacetylene, close to the level of silver and copper conductors. Next, frequent some major findings: in 1986, Eastman kodak company based on Dr Tang heterojunction organic solar cells, and in 1992, the university of California, Santa Barbara, Heeger and others found that high polymer material and fuller dilution receptor exciton separation phenomenon, the development of polymer heterojunction solar cells to provide the basis. In 1995, the university of Cambridge, Friend et al. And at the university of California, Santa Barbara, Heeger et al. Independently developed based on the structure of polymer and the receptor blend block heterojunction solar cells. So far, the basic structure of the polymer solar cells have been identified, and the rapid development over the next 20 years, even though they are with silicon-based solar cells in the application has the very big disparity. Taiwan hsinchu liao, tsinghua university, people have recently made a single block polymer solar cells, high energy conversion efficiency of the new record, the record of 9. 35%, the battery is based on a new type of polymer battery PTB7. In recent years, in order to simplify the manufacturing process, improve the stability of the equipment in different areas and environment and service life, the people we intensified the efforts on the commercialization of organic solar cells. For organic solar cells, with the rapid development in recent years has caused people's interest in the system the highest efficiency. As early as 1961, Shockley and Queisser inorganic semiconductor solar cells has been proved by the theoretical study of the energy conversion efficiency is about 30% limit, and the actual efficiency of inorganic solar cells is very close to this value by adopting the method of multi-junction form and concentrated form. Organic solar cells, and is one of the main difference between inorganic solar cells, organic solar cells in the active layer material with low dielectric constant, the close combination of exciton ( Electronic - Hole pair) 。 Exciton in the combination of what is known as the Frenker exciton, their binding energy usually at 0. Between 3 ~ 1 ev. This big binding energy can prevent exciton dissociation under electric fields. For organic electroluminescent devices, this phenomenon reduces the probability of exciton into the track of no radiation decay, guarantee the efficiency of electroluminescence. In the case of organic solar cells, which adds an extra step than inorganic photovoltaic process of solar cells. So light exciton in the organic solar cells have a certain amount of energy loss in the process of separation, general is 0. 3 - 0. 4 eV, which makes the researchers generally believe that the theoretical maximum efficiency should be lower than inorganic solar cells. It is generally believed that the heterojunction donor lowest occupied molecular orbital ( LUMO) The highest occupied molecular orbital (with receptors HOMO) Is the energy difference between the driving force behind Frenkd exciton dissociation. Real limits the efficiency of organic solar cell factors seem to be very simple, but in fact, they are very complicated, it is necessary to further discuss this problem.