CROSS-REFERENCE TO PRIOR APPLICATIONS

Priority is claimed to European Patent Application No. EP 18191861.6, filed on Aug. 30, 2018, the entire disclosure of which is hereby incorporated by reference herein.

FIELD

The invention relates to an organic material with a dipyrrin skeleton, and its synthesis and use in semiconducting devices, especially in organic semiconducting devices.

BACKGROUND

In organic electronics, interconnections of electrically conductive polymers or small organic molecules are used.

The invention relates to so-called “small molecules” that are non-polymeric organic molecules having a defined molecular structure and a molar mass between 100 to 2000 g/mol.

Organic electronic components can be, for example, displays, data memories or transistors, and in particular field-effect transistors. These devices also include organic opto-electronic devices such as organic photoactive devices. Such devices include solar cells and photodetectors comprising a photoactive layer in which charge carriers, e.g. bound electron-hole pairs (excitons), are generated. Further optoelectronic components are light-emitting electroluminescent components, which emit light when current flows through them.

Optoelectronic components comprise at least two electrodes, one electrode being applied to the substrate and the other acting as a counterelectrode. Between the electrodes is at least one photoactive layer, preferably at least one organic photoactive layer, as a light-absorbing layer, which may be formed as a mixed, or a stack of mixed and/or individual, layers. The inventors mean that under the at least one photoactive layer, a layer which actively contributes as an absorber layer by absorption of light contributes to the conversion of light energy into electrical energy. Additionallayers, for example transport layers, may be arranged between the electrodes. Further, a plurality of layer sequences can be stacked on top of each other between the two electrodes to form tandem or multi-stacked cells, wherein this layer sequence comprises at least one photoactive layer and at least one additional doped, undoped or partially doped layer as a transport layer, for example, pin/nip structures according to WO 2004/083,958 A2 or WO 2011/161,108 A1, and wherein each of these layers can consist of several layers.

Bura et al., J. Am. Chem. Soc. (2012), 134, 17404-17407 describes, for example, BODIPY dyes with iodoaryl radicals in the meso position of the dipyrrin skeleton and their use in solvent-processed organic solar cells.

WO 2015/036,529 A1 discloses the use of a pyrrolopyrrole-based compound in an apparatus of organic electronics.

WO 2010/133,208 A1 describes an organic semiconductor comprising a plurality of layers, wherein at least one of the layers comprises a material having an azabodipy skeleton.

SUMMARY

By using suitable novel organic materials, various novel components can be provided. As a result, the development of new applications that are thin, flexible, light and with colour variability, and also are inexpensive, is given.

There are currently known only a few NIR (near-infrared) absorbers in the range of 650 to 1400 nm for use in organic optoelectronics, especially in the area of non-polymeric compounds. NIR absorbers are of particular interest because they absorb in the non-visible region of the light spectrum and therefore appear transparent to the human observer, or, when used in combination with coloured absorbers, a wider range of the solar spectrum may be used.

NIR dyes known in the prior art are partially unsatisfactory. For example, their processability is not sufficient and/or they are not thermally stable during evaporation in vacuum. Typical organic infrared absorbers are cyanine dyes, used for optical recording media and described, for example, in DE 199 57 001 A1. Due to the ionic structure of cyanine dyes, extraordinarily high evaporation temperatures are expected, which cannot be achieved in practice because thermal decomposition of the dyes occurs before evaporation temperatures can be reached.

In addition, many NIR dyes known in the art do not have satisfactory thin film absorptivity due, for example, to improper film orientation, preferential orientation, low molar extinction coefficient, insufficient photostability, insufficient transport properties, or they do not fit energetically into the device. In addition, their synthesis is often too long and expensive for a technical application to be economical.

Technical Problem

Organic semiconducting materials are sought which absorb in the near-infrared (NIR) region between about 650 and about 1400 nm, and which, when applied in organic electronic devices, lead to an improvement in the properties of the devices. The NIR absorbers should be synthetically readily accessible, meaning their syntheses involve only a limited number of steps and no complex steps, and they should be suitable for the production of vacuum-processed organic components, in particular of vacuum-processed organic solar cells or photodetectors.

Ideally, the desired absorber materials have a suitable preferential orientation during layer growth, so that the absorbed radiation can be used via the favourable transport properties of the charge carriers.

Disclosure of the Invention and Technical Effect of the Invention

According to the invention, the technical problem is solved by compounds of general formula (I):



whereinn and m are each independently 0, 1 or 2,z1 and z2 are selected from the formulas (II) to (IV):

wherein in each of formulas (II) to (IV) one term “*” represents a potential point of attachment of the substituent z1 or z2 to the dipyrrin skeleton and the other term “*” represents a potential point of attachment to one of the aryl substituents Ar1 and Ar2,Ar1 and Ar2 are each independently selected from aryl or heteroaryl, wherein Ar1 in the case of n=0 and/or Ar2 in the case of m=0, corresponds to the formula (V), and “*” refers to the bonding site of the substituent Ar1 or Ar2 to the dipyrrin skeleton:

EWG is CN, or a fully or partially fluorinated, branched or unbranched, linear or cyclic alkyl chain, wherein hydrogen atoms of the alkyl chain may be substituted, and/or C atoms of the alkyl chain may be replaced by heteroatoms, preferably CN or CF3,X1 and X2 are selected from halogen, CN, alkyl, or fluorinated or partially fluorinated alkyl, alkenyl, alkynyl, alkoxy, aryl or heteroaryl,R1 to R4 are each independently selected from H, CN, halogen, or substituted or unsubstituted, branched or unbranched, linear or cyclic alkyl radical, andR5 and R6 are each independently selected from H, CN, halogen, or substituted or unsubstituted, branched or unbranched, linear or cyclic alkyl radical.

Further advantageous embodiments of the compounds according to the invention, as well as advantageous uses of the compounds, organic electronic components containing these compounds, and the synthesis of the compounds are the subject of further disclosure.

Advantageous Effect of the Invention

Surprisingly, it has been found that compounds of the invention, which on the one hand carry as a common structural element an electron withdrawing group on moiety EWG in the meso position of the dipyrrin skeleton, wherein the electron withdrawing group comprises either inductively withdrawing fluorine atoms or a cyano group which is both inductively and mesomerically withdrawing, or on the other hand carry in the 3,5-position of the dipyrrin skeleton a conjugated bond system characterized by a small spatial expanse, such as but not limited to, vinyl, alkynyl or furan units, broadly and strongly absorb near-infrared light. By contrast, the absorption of light in the visible range below 650 nm is relatively low, which is why the compounds according to the invention are suitable for the production of semi-transparent or transparent organic solar cells or photodetectors.

Furthermore, these compounds also have an increased charge carrier mobility, so that, in addition to photodetectors or solar cells, other organic electronic components comprising the compounds of the invention, such as transistors or OLEDs, may have improved electrical values.

The inventors have also found that the compounds of the invention can be used as charge transporting layers, e.g. as p-type materials, and thus it is possible to use them both in light-absorbing layers, as well as in charge carrier transport layers within a component.

The compounds of the invention are in particular “small molecules,” which are understood to be non-polymeric organic molecules having a defined molecular structure and a molar mass of between 100 and 2000 g/mol, which may in particular also be monodisperse.

In an embodiment, organic materials comprising compounds of the invention are applied in the form of thin films or small volumes onto substrates by printing, gluing, coating, vapor-deposition or other means. All processes which are also used for electronics on ceramic or semiconducting substrates are also suitable for the production of thin layers.

