Types of Organic Solar Cells

Table 1 Some state-of-the-art material combinations for different types of organic solar cells.

Working principles of organic solar cells are well described in a recent review and some monographs. More or less all types of organic solar cells described above comprise two components in the photoactive layer. One component serves as electron donor, whereas the other works as electron acceptor. Absorption of photons by the active layer components results in the electron transfer from donor to acceptor. This process called photoinduced charge transfer is a fundamental principle of operation of all known organic photovoltaic devices as well as the natural photosynthetic systems. In many cases, donor material is capable of efficient p-type transport and therefore can be called as p-type organic semiconductor. At the same time, electron acceptor material is denoted as n-type semiconductor in many cases. 

There are two main types of PSCs including bilayer heterojunction and bulk-heterojunction [7]. Bulk-heterojunction PSCs are more attractive due to their high surface area junction that increases conversion efficiency. This type of polymer solar cell consists of Glass, ITO, PEDOT PSS, active layer, calciiun and aluminum in which conjugated polymer are used as active layer [8]. The organic solar cells with maximum conversion efficiency about 6% still are at the begiiming of development and have a long... 

The donor-acceptor type small molecules reported on by Bazan and co-workers have proved to be excellent light-harvesting materials for use as donors in BHJ solar cells (Table 5.4). The simple, facile and reproducible synthesis, combined with excellent film forming capabilities and high device performance, make this class of materials well positioned to enable commercialization of organic solar cells. 

Fig. 17.5 Scheme of basic processes occurring in DSSCs (a) and organic solar cells (c). (b) Band bending for an n-type semiconductor and a p-type semiconductor in equilibrium with an electrolyte. 

Modern bacteria inhabit almost every ecological niche in the biosphere, and there are bacteria capable of using virtually every type of organic compound as a source of carbon and energy. Photosynthetic bacteria in both fresh and marine waters trap solar energy and use it to generate carbohydrates and all other cell constituents, which are in turn used as food by other forms of life. The process of evolution continues—and in rapidly reproducing bacterial cells, on a time scale that allows us to witness it in the laboratory. 

Liu prepared a sandwich type coordination compound (103) from porphyrin and phthalocyanine with the assistance of a microwave. The resulted compounds showed good solubility in conventional organic solvents. The photoelectric conversion properties have been tested with a Gratzel type cell. The results revealed that the sandwich type compound showed better photo-electric conversion efficiency than the corresponding monomeric porphyrin or phthalocyanine precursors. The short-circuit photocurrent of the solar cell with this sandwich type compound as sensitizer, was, as high as 691.31 A cm-2, which was much better, than those of porphyrin or phthalocyanine monomers [100]. 

The solar energy world finds itself on the horns of a dilemma, having to choose between metal-based solar cells, which perform well but are costly, and organic solar cells, which are cheap but inefficient. One answer is to combine the two types of semiconductor to produce a hy-... 

Possible applications of ZnO nanostructures are UV lasers (up to now only with optical excitation) [84], chemical sensors [85], or transparent substrates for thin film solar cells, e.g. as an alternative to Ti02 in injection type solar cells or in organic solar cells [79,86,87]. In the latter two applications the increased effective surface of arrays of ZnO nanowires leads to... 

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