In recent years, organic compounds with high absorption capabilities in the red and infrared spectral range have generated considerable interest because of their suitability for use in many fields of science and technology. For example, compounds of such kind can be used as active media in laser-driven recordable media such as CD or DVDs, or in solar cells to convert thermal radiation into electrical energy and in thermal insulation materials to prevent the interiors of closed spaces from overheating, in motor vehicles or display window areas for example. At the same time, compounds of such kind that absorb long-wave energy must also have the properties of absorbing practically no energy in the shorter-wave, visible spectral band as far as possible, and being thermally stable, so that they can be rendered usable for their respective purpose by vacuum evaporation processes, for example.
Many compound types that are capable of absorbing large quantities of light in the red and infrared spectral band besides being endowed with various other features defining their respective purposes have already been discovered in the past. In most cases, however, the spectrum of desired features is not available from one compound type alone. For example, polymethine dyes, most of which contain a polymethine chain of sufficient length to absorb a useful quantity of light in the red and infrared spectral band, have very low thermal stability which, due to their predominantly ionic nature, hinders non-decomposing evaporation. A similar situation applies for the products of oxidation of aromatic or heteroaromatic di- and polyamines, of the 4,4′,4″,4′″-tetrakis-(diarylamino)-N,N-tetraphenyl-benzidine type for example, and their aryl homologues, which absorb very long wave light in their oxidised state, but also vaporise poorly due to their ionic nature, and are thus unsuitable for many applications. In contrast to such compounds, nickel dithiolene complexes are also capable of absorbing very long-wave light in the infrared spectral band, and most are sufficiently thermally stable to evaporate readily, but their capacity to absorb light in the long-wave spectral band is often extremely low, so that in order to achieve absorption profiles in the IR spectral region with these compounds high concentrations or layer thicknesses must be used, which then frequently result in interference absorptions in the visible spectral band.
The only materials currently known for organic solar cells demonstrating absorption above 70 mm are compounds from the phthalocyanine series. These compounds are known for their high long-wave absorption and good stability, but because they are poorly soluble it is very difficult if not impossible to optimise them in terms of other properties such as the energy disposition of their surface orbitals.
The object of the present invention is therefore to provide semiconductor components that contain organic compounds with high absorption properties in the red and infrared spectral band, but which overcome the drawbacks of the related art and in particular are capable of non-decomposing evaporation for the purpose of manufacturing the component, that is to say they demonstrate good thermal stability and are able to absorb light in the long waveband.