Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K39/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic radiation-sensitive element covered by group H10K30/00
  • H10K39/30—Devices controlled by radiation
  • H10K39/36—Devices specially adapted for detecting X-ray radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
  • G01T1/16—Measuring radiation intensity
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
  • G01T1/16—Measuring radiation intensity
  • G01T1/24—Measuring radiation intensity with semiconductor detectors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/10—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising heterojunctions between organic semiconductors and inorganic semiconductors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/30—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/30—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
  • H10K30/35—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains comprising inorganic nanostructures, e.g. CdSe nanoparticles
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/10—Organic polymers or oligomers
  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
  • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene

Definitions

• the invention relates to a photodetector for X-radiation in which X-radiation is converted into electrical charge.
• the indirect method In the detection of X-rays, there is the direct and indirect conversion of the X-radiation into electrical charge, the indirect method has at least the disadvantage that initially the photon from the X-radiation interacts in a scintillator with a material that finally shows emission, the Scattered light produced. Due to the scattered light, the resolution of the indirect method is worse than with the direct method.
• organic photodiodes as known, for example, from WO 2007/017470, is only known in connection with indirect conversion. Otherwise, the technology of conversion of X-rays by photodetectors has so far only used inorganic photodetectors.
• organic compounds Compared to inorganic photodetectors, however, organic compounds have the decisive advantage that they can be produced over a large area.
• the object of the present invention is therefore to overcome the disadvantages of the prior art and to enable the direct conversion by means of organic photodetectors.
• the object of the invention and solution of the object is an organic photodetector for the direct conversion of X-radiation, on an electrode substrate, at least one active organic layer and on top of an upper electrode, incorporated in the active layer in a semiconductive organic matrix semiconducting nanoparticles are that allow the direct conversion of X-rays into electrical charges.
• the invention provides a process for producing a photodetector in which at least the organic active layer is prepared from solution ("wet-chemical").
• the organic photodetector according to the invention is characterized in that the conversion of the X-radiation takes place in the same layer as the generation of the charges. This ensures that a high resolution can be achieved for X-ray images. So far, this has only been possible with elaborate inorganic photodetectors. In general, various semiconducting nanoparticles or mixtures of different nanoparticles, for example in the form of crystals, can be used.
• semiconducting nanocrystals are incorporated into the semiconducting layer, which in turn are preferably prepared by chemical synthesis.
• Typical nanoparticles are Group II-VI or Group III-V compound semiconductors. It is also possible to use group IV semiconductors. Ideal nanoparticles show high X-ray absorption properties, such as lead sulfide (PbS), lead selenium (PbSe), mercury sulfide (HgS), mercury selenide (HgSe), mercury telluride (HgTe). Leading nanoparticles or nanocrystals in which quantization of the energy levels impinges (quantum dots) comprise diameters of 1 to typically 20 nm, preferably 1 to 15 nm and particularly preferably 1 to 10 nm.
• the starting material of the organic active layer of the photodetector is dissolved or as a suspension in a solvent and is produced by wet-chemical process steps (spin coating, knife coating, printing, doctor blading, spray coating,
• rollers, etc. are applied to a lower layer such as a charge-coupled device (CCD) or a thin film transistor (TFT) panel.
• a lower layer such as a charge-coupled device (CCD) or a thin film transistor (TFT) panel.
• the layer thicknesses are in the nanometer or micrometer range. Only a top electrode without structuring is necessary.
• the embedding of the quantum dots in the semiconducting organic, in particular polymeric, matrix can also be carried out with a multiple spray coating method. Such a method is described for example in the still unpublished 10 2008 015 290 DE as Multiples Spray Coating System for the production of polymer-based electronic components.
• Layers with thicknesses> 100 ⁇ m for direct conversion These layers can be produced at once by means of the abovementioned wet-chemical methods or by multilayer layers with a regular sequence of a semiconductor layer and an intermediate layer for constructing the overall layer.
• the semiconductor layer is in each case applied wet-chemically, for example by spin coating, knife coating, printing, doctor blading, rolling, etc.
• the intermediate layer preferably has good electron and hole transportability and prevents dissolution of underlying organic semiconductor layers during application of the upper layers.
• FIG. 3 shows the schematic structure of such a multilayer structure.
• Multilayer coatings can also be achieved, for example, by means of stacked photodiodes or photoconductors, as shown in FIG.
• the volume fraction of nanoparticles, such. As PbS, in the absorber layer is according to an embodiment of the invention very high (typically> 50%, preferably> 55% or more preferably> 60%) in order to ensure a correspondingly high absorption of the X-ray radiation.
• a metal layer is applied to the diodes, preferably over the encapsulation.
• FIG. 1 shows the typical structure of an organic photodiode
• FIG. 2 shows a pixelated photodetector with nanoparticles embedded in the active organic layer
• FIG. 3 shows a multilayer structure for achieving thicker layers and
• FIG. 4 schematically shows the structure of a stacked diode.
• FIG. 1 shows an organic photodiode 1. It comprises on a substrate 2 a lower, preferably transparent electrode 3, optionally a hole-conducting layer 4, preferably a PEDOT / PSS layer and above this an organic photoconductive layer 5 in the form of a bulk heterojunction with one above it
• the organic-based photodiodes have a vertical layer system, wherein between a lower indium-tin-oxide electrode (ITO electrode) and an upper, for example, calcium and silver electrode comprising a PEDOT layer with a P3HT PCBM blend.
• ITO electrode indium-tin-oxide electrode
• an upper, for example, calcium and silver electrode comprising a PEDOT layer with a P3HT PCBM blend.
• the blend of the two components P3HT (poly (hexylthiophene) -2-5-diyl) as absorber and / or hole transport component and PCBM phenyl-C61 as electron acceptor and / or electron donor acts as a so-called "bulk heterojunction", ie Separation of the charge carriers takes place at the interfaces of the two materials, which form within the entire layer volume.
• the solution can be modified by replacing or adding further materials.
• the organic photodiode 1 is operated in the reverse direction and has low dark current.
• nanoparticles are added to the active organic semiconductive layer.
• nanocrystals are used as nanoparticles.
• the suitability of the nanoparticle-modified X-ray conversion layer is achieved by the energy gap in semiconductor crystals, which can also be quantized as in the case of very small nanocrystals. If photons or high-energy X-ray quanta are absorbed with an energy greater than the energy gap of the semiconductor crystal, excitons (electron-hole pairs) are generated.
• the size of the nanocrystal When the size of the nanocrystal is reduced in all three dimensions, the number of energy levels is reduced, and the size of the energy gap between the quantized valence and conduction bands becomes dependent on the diameter of the crystal and thus their absorption or emission behavior changes.
• the energy gap of PbS of approx. 0.42 eV (corresponding to a light wavelength of approx. 3 ⁇ m) in nanocrystals with a size of approx. 10 nm can be increased to IeV (corresponding to a light wavelength of 1240 nm).
• X-rays which are absorbed by nanoparticles or nanocrystals, generate excitons.
• the resulting electron-hole pairs in the organic semiconductor are separated in the electric field or at the interfaces of organic semiconductors and nanocrystals and can flow through percolation paths to the corresponding electrodes as a "photocurrent".
• Figure 2 shows a schematic structure of a pixelated flat-panel photodetector with nanoparticles 7 embedded in the organic active layer 5.
• the conversion of the X-ray takes place directly in the organic photodiode.
• the BuIk heterojunction described above acts as electron acceptor or electron donor with embedded semiconducting nanoparticles or nanocrystals.
• the photodiode with glass substrate 2 which has a structured passivation layer 12 with vias 9 to the drain electrode 13 of the lower electrode layer 3, here are the nanoparticles 7 in the organic active layer 5 clearly visible (in sum me Frontplane).
• the glass substrate comprises, for example, an inorganic transistor array with a-Si TFT, that is, amorphous silicon thin-film transistors (backplane), which are commercially available.
• Passivation layers 12 and 8 serve to either encapsulate the photodiodes (eg, glass encapsulation) or to inhibit conductivity between individual a-Si TFT pixels.
• the optional hole transport layer 4 on which, in turn, the organic active layer 5 is located, which for example has a thickness in the range from 100 to 1500 ⁇ m, preferably approximately 500 ⁇ m.
• the upper structure is analogous to that known from FIG.
• An X-ray beam 14 striking a nanoparticle 7 is absorbed there and an exciton (not shown) is released therefrom.
• the result is a charge carrier pair, as shown, an electron 15 and a hole 16 comprising.
• FIG. 2 also shows that the substrate 2 and the lower passivation layer 12 together with the lower structured electrode 3 form the commercially available backplane 10, whereas the upper part of the device with the active organic layer 5 represent the front tarpaulins 11
• FIG. 3 shows a multilayer structure, which makes it possible to build up thicker layers by means of conventional wet-chemical methods.
• FIG. 4 shows a schematic structure of a stacked diode 1. Any thicknesses can be generated with n stacked diodes.
• the lower electrode 3, the optional hole transport layer 4, the organic active layer 5 with the nanoparticles 7, the cathode 6 and the upper intermediate layer 17 are only schematically visible.
• Nanoparticles or nanocrystals with defined diameters lead to reproducible absorbers with lower charge carrier trapping compared to mechanically comminuted and therefore poorly defined nanoparticles.
• diode fabrication on TFT panels for direct conversion of X-rays can be performed without the use of vacuum technology and classical semiconductor process technology.
• This invention involves the cost-effective production of a direct X-ray converter based on a composite of organic semiconductors and semiconducting nanoparticles which can be applied over a large area as organic photodiodes or photoconductors on flatbed scanners by wet-chemical processes.

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• 2008
  • 2008-06-25 DE DE102008029782A patent/DE102008029782A1/de not_active Ceased
• 2009
  • 2009-06-24 JP JP2011515364A patent/JP5460706B2/ja not_active Expired - Fee Related
  • 2009-06-24 EP EP09769268A patent/EP2291861A1/de not_active Withdrawn
  • 2009-06-24 US US12/737,264 patent/US20110095266A1/en not_active Abandoned
  • 2009-06-24 CN CN2009801245499A patent/CN102077352B/zh not_active Expired - Fee Related
  • 2009-06-24 WO PCT/EP2009/057864 patent/WO2009156419A1/de active Application Filing

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