DE102007019327A1 - Organic drift diode for single photon emission computed tomographic detector, has one electrode layer with type that does not correspond to another type of another electrode layer, and substrate arranged on side of photoactive layer - Google Patents

Abstract

The diode has a layer arrangement (3) arranged on a substrate (2). The arrangement includes an electrode layer (4). A photoactive layer (5) is arranged adjacent to the electrode layer. Another electrode layer (6) is arranged adjacent to the photoactive layer. One of the electrode layers includes a drift structure (7) and an electrode type, and the other electrode layer includes another electrode type that does not correspond to the former type. The substrate is semi-transparently arranged on a side of the photoactive layer. The substrate is one of plate, semiconductor wafer or a polymer foil. An independent claim is also included for a procedure for manufacturing an organic drift diode.

Description

The The invention relates to an organic drift diode with outer Terminals, as well as a method for producing a organic drift diode.

in the Nuclear Medicine is known to detect detectors as well as for the spatial and energetic measurement of gamma radiation use. For example, in the single photon emission Computed Tomography (SPECT) detected single photons. To it is known in the art to use in a scintillator material, For example, sodium iodide, avalanches photons of visible light which then pass through a two-dimensional array of photomultiplier tubes be detected. A photon or gamma quantum leads thereby to emit many thousands of visible photons through the non-directional emission and light scattering in each case several photomultiplier tubes to reach. By a weighting of several photomultipliers at the same time measured signals becomes a spatially resolved Received signal of a single gamma quantum event. By summation The signal height of the different tubes will also increase receive energy information for the event. This Operating principle is generally referred to as Anger camera.

One major disadvantage of the described technology is first due to the relatively large size of the photomultiplier tubes given. This will cause the spatial resolution limited to a few millimeters and the detector system has large Overall dimensions. The large volume of the entire detector unit in turn leads to the use of a larger one Amount of lead shielding since the detector is protected from scattered gamma and X-rays from other spatial directions than the desired must be protected to incorrect measurements to avoid. In particular, by the lead shield results thus a very high weight, that during the measurement with the corre sponding support structure must be moved together. Furthermore, such designed detectors for use in nuclear medicine disadvantageous because the photomultiplier tube not compatible with magnetic fields, so far the use of combined magnetic resonance / SPECT devices not realized could be.

Therefore was proposed instead of photomultiplier tubes To use solid state detectors. One of the examined Possibilities is the use of photodiodes. A requirement however, this is because the photodiodes are read very low noise so that the detection of individual events while determining the energy of the gamma quantum or photon remains possible.

US 2004/0159793 proposes to use organic photodiodes in radiation detectors for nuclear medicine. An advantage of the organic photodiodes for this application is that these detector devices can be manufactured significantly cheaper than silicon diodes or other inorganic semiconductor diodes by inexpensive manufacturing processes, such as spin coating, doctor blade, printing, spraying or vapor deposition, especially on larger areas. Naturally, detectors in the field of nuclear medicine are usually large-area components, since the field of view of the detector corresponds to the dimensions of the body parts to be examined, thereby achieving total areas in the three- to four-digit square centimeter range.

organic Photodiodes have the known flat structure, in which a large-area anode of a large area Opposite cathode. In between is the photoactive material. This results in a fundamental disadvantage of organic Photodiodes for use in radiation detectors for single gamma quanta. Such organic photodiodes have a typically have relatively high diode capacitance through Increase the noise at the signal amplifier the achievable energy resolution limited.

This high capacity is mainly determined by the dimension of the layer structure, because the typical layer thicknesses of the organic semiconductor layers are in the range of 100 to 500 nm. These layer thicknesses are very low in comparison to typical silicon diodes. On the other hand, it is difficult to make the layers substantially thicker (greater than 1 μm), since the efficiencies of the organic diodes would be significantly reduced due to the comparatively low charge carrier mobility and lifetime. At layer thicknesses of up to 500 nm, organic photodiodes are very efficient, especially in the visible, with external quantum efficiencies ranging from 50 to 90%. Since the dielectric constants of the organic semiconductors are in the range of 3 to 6, diode capacities are from 5 to 50 nF per cm ² . In comparison, the capacitance of a typical silicon photodiode having a thickness of 150 μm is only about 70 pF per cm ² .

Of the The present invention is therefore based on the object, an organic Element for detecting gamma quanta with reduced noise, good quantum efficiency and favorable production.

In order to achieve this object, it is provided according to the invention in the case of an organic drift diode with external terminals that it comprises a substrate and a layer arrangement arranged on the substrate Starting from the substrate-next layer, the layer arrangement comprises a first electrode layer, a photoactive layer arranged adjacent to the first electrode layer comprising an organic semiconductor mixture of an electron-transporting and a hole-transporting material and a second electrode layer arranged adjacent to the photoactive layer, wherein one of the electrode layers has a drift structure and a first type of electrode selected from the anode or cathode selection group, and the other electrode layer comprises an extended second electrode type selected from the selectable group and not corresponding to the first type of electrode, and the entirety of the layers and optionally the substrate on at least one Side of the photoactive layer is formed at least semitransparent.

The The basic idea of the present invention is therefore the concept of organic solid state detectors on the principle to transmit known as a silicon drift diode drift diode. Unlike silicon diodes is used in an organic photodiode the functionality is not determined by the doping Partial layers, but by the composition of electron and hole transport components as well as through selectivity achieved the electrode contacts. Unlike a silicon drift diode Therefore, a different structure and a different processing is required. As the photoactive layer is in the inventive organic drift diode an organic semiconductor mixture of a electron transporting and a hole transporting material applied. This forms a variety of transitions between the electron transporting and the hole transporting Material, at which transitions a space charge zone arises in which occurs when hitting a gamma quantum charge separation. Such a structure is also called bulk heterojunction. For example as the first type of electrode an anode, as the second type of electrode a Cathode selected, so is on one side of the photoactive layer an extended, the photoactive layer in particular completely covering Cathode provided, which serves for the extraction of the electrons. Therefore becomes a material with low work function, approximately in the range of 1.5-4 eV, and good electron transport properties used. The opposite anode, which is for extraction the resulting holes (positive charge carriers) serves and therefore preferably a material with high work function, for example, 4-6 eV, has a small extent. To be extracted holes are using the drift structure, to which a corresponding potential has to be applied and which ultimately also form cathodes, moved by a drift towards the anode, by a corresponding potential distribution along the drift structure a corresponding electric field within the photoactive layer is produced. These remarks apply analogously when the the first type of electrode is a cathode and the second type of electrode is a cathode Anode is.

In the structure according to the invention, it is therefore possible to significantly reduce the capacitance and thus the noise when the signal is read out. The capacity of the diode is no longer dependent on the total diode area, but is determined only by the much smaller dimension of the first type of electrode. Thus, depending on the exact geometry, capacities can be achieved in the range of a few 10 pF per cm ² . This opens up applications that require low-noise readout, for example in SPECT detectors.

Farther is the organic drift diode according to the present invention Invention on larger areas cost produced. It is thus a cost-processable Detector described.

After all is counteracted yet another disadvantage of organic photodiodes. There With very large detector areas, the dark current increases and the probability of short circuits. The dark current and the shorts are often on "leaking" areas attributed to the otherwise selective contacts. When implemented as a drift diode, depending on the exact geometry of the Structure, the area of the "leaking" anode or Cathode contact can be reduced. Thus, a reduction of Dark current density and a reduction in the number of defects per area possible.

The The organic drift diode described above should basically have at least four outer terminals, namely an outer anode connection for the anode, an external cathode connection for the cathode and at least two drift structure connections, in particular an innermost and an outermost Drift structure connection, for the drift structure. The drift structure connections are expediently at the innermost and contacted at the outermost edge of the drift structure, so that the corresponding drift field can be generated. At a Drift structure of concentric rings, for example, the innermost ring and the outermost ring with an outer ring Driftstrukturanschluss be connected.

As already shown, it is the organic drift diode not a "free-floating" structure, but a substrate is required on which the layer arrangement is arranged is. This ultimately leads to two basic, alternative embodiments of the present invention.

First can be provided that the second electrode layer, the second Electrode includes. In this case, therefore, are the drift structures and the first type of electrode between the substrate and the photoactive layer are thus applied first during manufacture. Since the Photoaktivschicht usually either from solution or by thermal evaporation, there is a risk that the drift structure and the first type of electrode are oxidatively attacked become. Therefore, it can be provided in an advantageous embodiment, that the drift ring structure and the first type of electrode made of oxidation resistant Materials exist. In addition, it has in this first embodiment proved to be advantageous when the second electrode layer semitransparent is trained. Then the incidence of light from the substrate take place on the opposite side of the photoactive layer, because the second electrode layer has a high transmission.

alternative to this first embodiment can in a second Embodiment be provided that the first electrode layer The second type of electrode therefore includes the second type of electrode between the photoactive layer and the substrate is arranged. The drift structure and the first type of electrode are then on the side facing away from the substrate arranged. In this case, it is advantageous if the second type of electrode consists of an oxidation-resistant material. To the light it can be provided that at least the substrate and the first Electrode layer are designed at least semi-transparent, so that the photons are coupled through the substrate here can. As a substrate in this case, for example Glass to be used.

in principle Of course it is also possible to put the light over the electrode layer with the drift structure and the first type of electrode couple. However, the side with the extended electrode type more advantageous as it is a homogeneous and in particular thinner Layer represents. In the case of the finely structured drift structure or the first type of electrode can unwanted optical Effects like scattering or reflection occur. It is also for the drift structure and possibly also the first type of electrode are advantageous, make the layers slightly thicker, which greatly increases light entry would hamper.

Especially in the first embodiment, but also in the second Embodiment may be provided with particular advantage be that the outer ports are on the side of the substrate facing away from the layer arrangement are provided and via via with the respective electrodes, So the anode, the cathode and the drift structure are connected. This is particularly useful if several Drift diodes as far as possible filling surfaces to be merged into a detector array. in the In the case of such a drift diode array, it is also advantageous that the organic drift diodes also directly on a wafer, for example a silicon wafer, or a ceramic substrate as a substrate can be. Not only in this case, but also in general can then advantageously the drift diode a particular of first Elekrodenart adjacent field effect transistor or amplifier include. It can also be provided that the field effect transistor is an organic, is in the layer arrangement integrated field effect transistor.

The Electrode or the electrodes of the second electrode layer can by wire bonding with the or the corresponding outer Be connected to terminals. In the case where the second Electrode layer of the drift structure and the first type of electrode is formed, this is the simplest Kontaktierungsvariante represents.

Especially in the event that the first electrode layer is the drift structure and the anode comprises, it is expedient if the layer arrangement facing the substrate, a conductor track layer for connecting at least part of the electrodes to the corresponding ones provided on the substrate outer terminals and a passivation layer for isolation over the remaining layers. It is, for example conceivable that the outer connections at the edge of the substrate in a not covered by the layer arrangement Are arranged area, which then led to corresponding conductor tracks become. Of course, in this way Also, any vias are arranged arbitrarily. A particularly advantageous embodiment results when the second electrode layer comprises the second type of electrode which laterally to a corresponding contact pad on the larger as the layer arrangement dimensioned substrate is extended. The second type of electrode is accordingly laterally over the Photoactive layer down to a corresponding contact pad, the may form part of the wiring pattern or directly with connected to the corresponding external connection is. This is a wire bonding or other method of contacting no longer necessary from above, so that a particularly compact Configuration of the drift diode is made possible.

The semiconductor mixture is particularly advantageously designed as a bi-continuous bulk heterostructure. Bi-continuous in this case means that the mixture is structured such that charge carriers from each location in the photoactive layer to the corresponding electron-transporting or hole-transporting material Electrodes can be performed. Such a bi-continuous structure is made possible by appropriate treatment of the photoactive layer in the production of the drift diode, for example by annealing.

The For example, the electron-transporting material may be the fullerene C60, a C60 derivative or phenyl-C61-butyric acid methyl ester (PCBM) be. Particularly useful is the use proven by PCBM.

For the hole transporting material may be a polyphenylenevinylene derivative, in particular MEH-PPV (poly [2-methoxy-5- (2'-ethyl-hexyloxy) -1,4-phenylenevinylene]) or a substituted thiophene, especially poly-3-hexylthiophene (P3HT) or poly-3-octylthiophene (P3OT). there P3HT is preferred.

The Thickness of the photoactive layer can be from 100 to 500 nm, in particular 200 nm. It should be chosen so that one highest possible quantum efficiency is achieved and yet the charge carriers can reach the respective electrodes.

In Another embodiment of the invention, the layer arrangement between the photoactive layer and the first and / or second electrode layer another organic semiconductor layer, namely a electron transporting or a hole transporting transport layer include. Such an organic transport layer can, for example consist of Pedot (Polyethylendioxytiophen).

As already mentioned, the electrode contacts should have a specific Have selectivity. This should be the anode for extraction the resulting positive charge carriers (holes) consist of a material with high work function, the cathode against it for extracting electrons from a low work function material. Similar requirements apply to the drift structure as for the second type of electrode. Accordingly, can for example, the indium tin oxide (ITO), gold, silver, Platinum, palladium or a mixture of these substances. The cathode can be made of indium tin oxide (ITO), aluminum, magnesium, Silver, calcium, an inorganic salt, especially lithium fluoride, Sodium fluoride or cesium fluoride, or a mixture consist of these substances. When choosing the materials is especially note that the ones used in the first electrode layer Materials should be as resistant to oxidation as possible. As a particularly suitable material has indium tin oxide (ITO) proved, as it combines several advantages. For one thing, it can be for Both types of electrodes are used because the work function and the transport properties through the stoichiometry and the type of processing can be varied. To the Others ITO is transparent and stable.

Process Technically, so in the context of production, it is particularly favorable when the first type of electrode and the drift structure are different Materials exist. Then both materials can be successively processed accordingly, so applied and structured.

The first type of electrode and / or the drift structure can thereby have a thickness of 100-300 nm, in particular 200 nm. The second type of electrode can be made thinner and a thickness of 10-30 nm, in particular 20 nm.

For the substrate are a variety of advantageous embodiments conceivable. Thus, the substrate may be made of glass, ceramic or metal or a semiconductor wafer, a circuit board or a foil, in particular a polymer film. Glass or a foil are particularly suitable if the substrate is to be configured at least semitransparent. In a semiconductor wafer, a ceramic substrate (e.g. from LTCC) or a printed circuit board are particularly favorable through contacts or the integration of a field effect transistor or amplifier possible.

The Substrate may generally have a thickness of 0.5 to 1 mm, in particular 0.7 mm.

To protect the sensitive substances from oxygen and moisture, it can be expediently provided that the drift diode comprises an encapsulation for protecting the layer arrangement. Such a passivating encapsulation, which protects against environmental influences, can be realized in various ways. For example, it is conceivable that the encapsulation comprises a glass or metal substrate which covers the drift diode from the side of the second electrode layer. Advantageously, the glass or metal substrate of the encapsulation is at least so large that it covers the layer arrangement, in particular the stack structure of the first electrode layer, the photoactive layer and the second electrode layer, and even projects slightly beyond it. In this case, however, the area of the glass or metal substrate is smaller than the area of the opposing substrate, so that access to external terminals, which can be arranged, for example, at the edge of the substrate, is simplified. Alternatively or additionally, the encapsulation may comprise at least one thin layer of organic and / or inorganic material, in particular silicon nitride, silicon oxide, aluminum oxide, aluminum oxynitride, epoxy, parylene or polyacrylate. Such a design protects the drift diode on all sides against environmental influences. It is particularly useful when wire bonding is used for contacting. Then, before the actual inorganic passivation (from nitride or oxide), a first organic passivation layer (made of epoxy, polyacrylate or parylene), which wraps the wires and provides a relatively smooth surface for the further, inorganic coating, can first be applied.

to Improvement of the detector properties of the drift diode can be provided be that the electrode layer comprising the drift structure in addition includes at least one guard electrode for field degradation. Such guard electrodes are basically known and serve to field the field of the side facing away from the anode of the drift structure so that as little loss of generated charge carriers may occur. Such guard structures comprise at least a guard electrode made of similar materials the above-mentioned electrodes can exist. About one another external connection is the guard electrode brought to the appropriate, ideal for field shaping potential.

The design of the drift structure can be advantageously carried out in various ways in the drift electrode according to the invention, depending on the application. Thus, it may be provided that the drift structure comprises spaced-apart, concentric ring electrodes or polygonal electrodes or an extended ring electrode or polygonal electrode or circular electrode or square electrode or a spirally outwardly extending spiral electrode. The "classical" arrangement comprises various, concentric, mutually unconnected ring electrodes (drift rings), of which with a diode area of 1 cm ^2, typically about 10 to 100 are provided, whereby most of the innermost and the outermost ring is connected to an external terminal. Alternatively, however, it can also be provided that a spiral-type drift structure is used in which the potential difference along the spiral is achieved by means of a higher sheet resistance If a spiral electrode is used, then the innermost part of the spiral electrode can also be connected to the first type of electrode Finally, it is also possible to realize the drift structure as a continuous resistance layer, for example a circular electrode, in which case the sheet resistance should be slightly higher than for a spiral electrode and again the innermost contact can be saved. In order to enable a better packing ratio, for example when used in a SPECT detector, it is possible to deviate from the round geometry and polygonal geometries can be used. Hexagonal or rectangular structures are particularly suitable for dense packing.

to Arrangement of the first type of electrode in the drift structure are two Alternatives are conceivable and feasible. The first type of electrode can be arranged in the center of the drift structure, but also the drift structure surround. In the second case is a larger area first type of electrode necessary.

In further advantageous embodiment can also be provided in that the drift structure comprises spaced, parallel strip electrodes and the first type of electrode as parallel to the strip electrodes formed the drift structure extending strip electrode and adjacent to an outer strip electrode the drift structure is arranged. In this way, a linear constructed organic drift diode realized. Such a detector can also be used for position determination, as over the time delay of the signal to the radiation entrance determines the drift path perpendicular to the drift strip electrodes can be.

Besides the invention also relates to a process for the preparation of a organic drift diode. As for the two embodiments already mentioned, is the case in which the drift structure on the substrate side is (first embodiment) to distinguish from the case in which the drift structure on the side facing away from the substrate is arranged (second embodiment). Both realization possibilities put different demands on the processing, the be presented together with their solution now.

in the first case, so for the substrate side arranged combination from drift structure and first type of electrode, there is the difficulty therein, the electrode material, in particular lower Work function, structured and not by the subsequent Attack process steps. Is the first type of electrode the Anode, should the drift structure so basically for the cathode can be made of suitable materials, so can For example, not extremely sensitive to oxidation materials like calcium or barium.

• a) Zu einer ersten Elektrodenstruktur strukturiertes Aufbringen einer ersten Schicht aus einem ersten Material mit geringer oder keiner Oxidationsneigung auf ein Substrat oder ein mit wenigstens einer grundlegenden Schicht versehenes Substrat und zu einer zweiten Elektrodenstruktur strukturiertes Aufbringen einer zweiten Schicht aus einem zweiten Material mit geringer oder keiner Oxidationsneigung auf das Substrat, wobei die eine Elektrodenstruktur eine Driftringstruktur und die andere Elektrodenstruktur eine erste Elektrodenart, gewählt aus der Wahlgruppe Anode oder Kathode, ist und beide Elektrodenstrukturen eine erste Elektrodenschicht bilden,
• b) Aufbringen einer Photoaktivschicht aus einer organischen Halbleitermischung aus einem elektronentransportierenden und einem lochtransportierenden Material aus Lösung oder durch thermisches Verdampfen auf die erste Elektrodenschicht, wobei insbesondere außerhalb der ersten Elektrodenschicht liegende Bereiche des Substrats durch eine Schattenmaske abgedeckt sind,
• c) Aufbringen einer zweiten Elektrodenschicht als zweite Elektrodenart, die aus der Wahlgruppe gewählt ist und nicht der ersten Elektrodenart entspricht, aus einem dritten Material auf die Photoaktivschicht, insbesondere durch physikalische Gasphasenabscheidung.

To solve this problem, the following steps are provided according to the invention in a first method for producing an organic drift diode:

• a) to a first electrode structure structured application of a first layer of a first material with little or no tendency to oxidation on a substrate or provided with at least one basic layer substrate and structured to a second electrode structure applying a second layer a second material with little or no tendency to oxidize on the substrate, wherein the one electrode structure is a drift ring structure and the other electrode structure is a first type of electrode selected from the anode or cathode selection group and both electrode structures form a first electrode layer,
• b) applying a photoactive layer of an organic semiconductor mixture comprising an electron-transporting and a hole-transporting material from solution or by thermal evaporation onto the first electrode layer, wherein regions of the substrate lying outside the first electrode layer in particular are covered by a shadow mask,
• c) applying a second electrode layer as a second type of electrode, which is selected from the selection group and does not correspond to the first type of electrode, from a third material to the photoactive layer, in particular by physical vapor deposition.

starting point of the method is a substrate, as it regards The organic drift diode according to the invention already closer was explained. This substrate can already with at least be provided with a basic layer, such as a Conductor layer and a passivation layer. It lies however also in the context of the procedure, the basic layer or the to apply basic layers first. If necessary be provided with at least one basic layer substrate now in two consecutive steps structured two electrode structures applied, one of which is the drift structure, the other the anode or the cathode forms. Under structured application here is also to understand that first a layer is applied, which is first structured in a subsequent step. advantageously, Both the first and the second material are different, so that both Electrode structures can be processed one after the other. It is now envisaged that both the first material and the second material has little or no tendency to oxidize, So are essentially resistant to oxidation. This is in view to the subsequent steps advantageous to oxidation and thus to avoid a lower quality organic drift diode.

After that the photoactive layer is applied in step b). This consists from an organic semiconductor mixture, also called a semiconductor blend, from an electron transporting and a hole transporting Material. The application can be made of solution or by thermal Evaporate the first electrode layer. It can expediently outside the first electrode layer lying areas of the substrate covered by a shadow mask become. This way, if necessary, outside of the region of the first electrode layer provided outer Protected connections or the like.

After all In a step c), the extended second type of electrode is called applied second electrode layer. The second type of electrode is then in turn, a cathode when the first type of electrode is the anode or the other way around. A preferred method for application The second electrode layer is the physical vapor deposition.

On this way becomes a high quality invention organic drift diode after the first already discussed above Embodiment won. The procedure is without much effort and cost effective and allows the Production of large-scale organic drift diodes as for example in nuclear medicine applications for detection of gamma quanta or photons are needed.

As already mentioned, the structuring of the electrode structures the first electrode layer even after the application of the corresponding Materials are made. Then it can be provided that a particular lithographic structuring of the first material to the first Electrode structure and a particular lithographic structuring of the second material to the second electrode structure. Lithographic structuring is a well known and excellent suitable type for subsequent structuring, the implementation of the first method further simplified. Another variant to subsequent structuring would be, for example the nanoimprint process. In principle, the first Layer and the second layer but also already structured when applied be, for example, by a shadow mask or by printing such as pad printing, screen printing or flexographic printing. In the mentioned printing process However, it is more difficult, the fine size scale to realize the third structure or the first type of electrode exactly.

For the second electrode layer may advantageously be at least one semitransparent material can be used so that when manufactured organic drift diode, the light from the side facing away from the substrate Page is provided. This has already been regarding the Discussion of the drift diode according to the invention mentioned Advantages.

With regard to the second embodiment of the drift diode according to the invention, a drift diode is to be created in which the extended type of electrode is located on the side of the layer arrangement facing the substrate. This means, in this case, the electrode structures, ins special the drift structure, are applied to the photoactive layer structured. It should be noted that it is no longer possible to apply wet-chemical processes above the organics.

• a) Aufbringen einer ersten Elektrodenschicht aus einem Material mit geringer oder keiner Oxidationsneigung als erste Elektrodenart, gewählt aus der Wahlgruppe Anode oder Kathode, auf ein Substrat oder ein mit wenigstens einer grundlegenden Schicht versehenes Substrat,
• b) Aufbringen einer Photoaktivschicht aus einer organischen Halbleitermischung aus einem elektronentransportierenden und einem lochtransportierenden Material aus Lösung oder durch thermisches Verdampfen auf die erste Elektrodenschicht, wobei insbesondere außerhalb der Elektrodenschicht liegende Bereiche des Substrats durch eine Schattenmaske abgedeckt sind,
• c) Mittels einer Schattenmaske oder einem Druckverfahren zu einer ersten Elektrodenschicht strukturiertes Aufbringen einer ersten Schicht auf die Photoaktivschicht und mittels einer Schattenmaske oder einem Druckverfahren zu einer zweiten Elektrodenstruktur strukturiertes Aufbringen einer zweiten Schicht auf die Photoaktivschicht durch physikalische Gasphasenabscheidung, wobei die eine Elektrodenstruktur eine Driftstruktur und die andere Elektrodenstruktur eine zweite Elektrodenart, die aus der Wahlgruppe gewählt ist und nicht der ersten Elektrodenart entspricht, ist und beide Elektrodenstrukturen eine zweite Elektrodenschicht bilden.

According to a second method for producing an organic drift diode, the following steps are therefore provided according to the invention:

• a) applying a first electrode layer of a material with little or no tendency to oxidation as the first type of electrode, selected from the anode or cathode selection group, to a substrate or a substrate provided with at least one basic layer,
• b) applying a photoactive layer composed of an organic semiconductor mixture comprising an electron-transporting and a hole-transporting material from solution or by thermal evaporation onto the first electrode layer, wherein regions of the substrate lying outside the electrode layer, in particular, are covered by a shadow mask,
• c) applying a first layer to the photoactive layer structured by means of a shadow mask or a printing method to a first electrode layer and applying a second layer to the photoactive layer by physical vapor deposition by means of a shadow mask or a printing method, wherein the one electrode structure has a drift structure and the other electrode structure is a second type of electrode that is selected from the selection group and does not correspond to the first type of electrode, and both electrode structures form a second electrode layer.

in the Accordingly, the second method does not require subsequent structuring the drift structure and the type of electrode performed to due to the wet-chemical processes, the photoactive layer is not to damage. This will be a high quality and inexpensive and on large areas producible organic drift diode according to the invention of the second embodiment. The others Remarks on the remaining steps regarding of the first method are also applicable here.

at This second method can advantageously at least one semitransparent substrate, especially glass, and a semi-transparent material be used for the first electrode layer. The light incident then takes place from below through the homogeneous layers and will not due to the inhomogeneous structuring in the area of the drift structure and The second type of electrode disturbed.

In terms of the choice of material and the thickness of the individual layers and the exact structuring of the drift structure is with respect to both methods with respect to the inventive Drift diode referenced statements already made. These and other embodiments of the invention Drift diode are fully based on the invention Method transferable.

in the Embodiments are now presented below, which in principle for both methods of the invention are applicable.

One preferred method for applying the first electrode layer is the physical vapor deposition, in particular sputtering. This can be realized inexpensively and easily.

The For example, the photoactive layer may be made from solution Spray coating can be applied. In particular, the application is suitable the semiconductor mixture of preferably 1% solution in Xylene. For example, an organic semiconductor mixture may consist of PCBM and P3HT in concentration ratio 1: 1 from 1% Solution in xylene by spray coating in one layer thickness of 200 nm, for example.

As already with respect to the invention Drift diode discussed, in particular, is the formation of a bi-continuous Bulk heterojunction advantageous for the detector properties the organic drift diode. Therefore, may be provided appropriately be that between the steps b) and c) a tempering of the photoactive layer is carried out. By annealing the photoactive layer for example, at 100 ° C for 15 minutes becomes one partial separation of the mixture into a bi-continuous network achieved on sub-micron scale, thus increasing the extraction efficiency the charge carrier improved.

In further embodiment of the method according to the invention it can be provided that the application of the second electrode layer at low deposition rates, in particular at about 1 Å / s becomes. Such slow evaporation has an advantageous effect the dark current characteristic.

to Contacting of the individual electrodes with outer Connections are several variants conceivable. Advantage is it, as already shown above, in particular, if connections provided on the side facing away from the layer arrangement of the substrate are. Then, as part of the procedure before step a) vias of the substrate to connect the electrodes with external connections on the layers away side of the substrate are created.

Should alternatively, the outer terminals, for example be provided at the edge of the substrate or should the positions the vias selected as freely as possible can be, so before step a) a Printed circuit layer with structured printed conductors and contact pads and apply a structured passivation layer, that form the basic layers. To apply the basic Layers can first be obtained by physical vapor deposition, especially by sputtering, a conductive material on the substrate applied and then in particular lithographically be structured, after which a Passivierungsmaterial by physical Gas phase deposition, in particular by sputtering, is applied and in particular lithographically structured, so that the contact pads are not covered by the passivation layer. When Material for these tracks, for example, aluminum can be used, but other materials are conceivable. The Passivierungsmaterial can be, for example, SiNx, which also by chemical vapor deposition can be applied. Important is that the outer connections and the contact pads for the electrodes remain free.

The Electrode or the electrodes of the second electrode layer can for example by wire bonding, in particular under an inert gas stream, be connected to external terminals. This is particularly useful when the second electrode layer includes the drift structure. Includes the second electrode layer only the extended type of electrode, this can be advantageous be structured so that they pass over the photoactive layer on a contact pad for an outside Connection is pulled down. In this case, then no Drahtbonding required. If a wire bonding is done, so should advantageously done under inert gas, so that still none protected by an encapsulation layers none Be exposed to oxidation. In this context it is too useful, in the second electrode layer mixtures of different Materials to use, with the last applied material as resistant to oxidation as possible.

As already mentioned, the inventive Method include a step in which an encapsulation for protection of the layers is applied. For example, it is conceivable a glass substrate and / or a ceramic substrate on the second Electrode layer is adhered. This is particularly advantageous feasible if no wire bonding is used. alternative or in addition, as a thin encapsulation Layer or layer sequence of organic and / or inorganic Material, in particular silicon nitride, silicon oxide, aluminum oxide, Aluminum oxynitride, epoxy, parylene or polyacrylate, applied become. If wire bonding is used, then before the actual inorganic encapsulation first, a first organic Encapsulation layer are applied to the bonding wires wrapped and a relatively smooth surface for the further, inorganic encapsulation layer available provides.

Generally may include the drift structure when applying the layers Electrode layer a third as guard electrode or guard electrodes structured layer applied as part of the electrode layer become. The operation and advantages of guard electrodes were with respect to the invention Drift diode already discussed.

With particular advantage can be found in particular in the basic layers integrated a particular organic field effect transistor applied or be attached.

Further Advantages and details of the present invention will become apparent from the embodiments described below as well as from the drawings. Showing:

1 a cross section through a first embodiment of an organic drift diode according to the first embodiment,

2 a cross section through a second embodiment of an organic drift diode according to the first embodiment,

3 a cross section through an organic drift diode according to the second embodiment,

4 - 9 possible embodiments of the drift structure and the first type of electrode,

10 a first arrangement of a plurality of organic drift diodes for use in a SPECT detector,

11 a second arrangement of a plurality of organic drift diodes for use in a SPECT detector, and

12 a drift structure with associated electrode for a linear organic drift diode.

It should be noted in advance that, for the purpose of simplifying the illustration, exemplary embodiments are assumed in which the anode with the drift structure forms an electrode layer. Of course, however, the invention also extends to arrangements in which the cathode with the drift structure forms an electrode layer and the anode represents the extended type of electrode.

1 shows a first embodiment of an organic drift diode 1 according to the first embodiment of the present invention. The drift diode 1 includes one on a substrate 2 arranged layer arrangement 3 consisting of a first electrode layer 4 , a photoactive layer 5 and a second electrode layer 6 consists. In this case, the first electrode layer comprises 4 a drift structure 7 here in the form of drift rings, an anode 8th as the first type of electrode and a guard electrode surrounding the drift rings 9 , The second electrode layer 6 includes an extended cathode 10 as a second type of electrode. Through a glued glass substrate 11 the drift diode is protected from damaging influences. The glass substrate 11 covers the entire layer arrangement 3 ,

The cathode 10 is semitransparent, allowing light, as indicated by the arrows 12 indicated by the glass substrate 11 and the cathode 10 into the photoactive layer 5 can penetrate, where it comes in the known manner to the formation of positive and negative charge carriers. The photoactive layer 5 comprises an organic semiconductor mixture of an electron-transporting and a hole-transporting material, which form a bi-continuous bulk heterostructure. This means that resulting pairs of charge carriers can reach the corresponding electrodes via the corresponding material of the semiconductor mixture. It is characterized by the drift structure 7 generates an electric field through which the holes for extraction of the anode 8th be supplied. The basic functional principles of the drift diode are well known from silicon drift diodes and are not intended to be detailed here.

For manufacturing reasons is for the anode 8th and the drift structure 7 as well as the guard electrode 9 each chosen an oxidation resistant material.

The substrate 2 here has a thickness of 0.7 mm and is a semiconductor wafer. Of course, it is also conceivable to use other materials for the substrate, for example a glass substrate, a metal substrate, a ceramic substrate (in particular LTCC), a film, in particular a polymer film, or a printed circuit board. Advantageously, adjacent to the anode here is a field effect transistor 13 in the substrate 2 integrated, allowing a first signal processing already in the organic drift diode 1 can take place. Alternatively, it is also conceivable to integrate an organic field-effect transistor as a layer structure. In addition, an amplifier may be provided.

On the substrate is the first electrode layer 4 applied. This comprises three different electrode structures, namely the anode 8th , which is circular and centrally located, the drift structure 7 whose concentric rings are the anode 8th equidistantly surrounded as well as a guard structure, formed by the guard electrode 9 , which is also annular and the drift structure 7 surrounds. The guard electrode 9 , the drift structure 7 and the anode 8th are made of different materials so that they could be processed one after the other during production. All three electrodes 7 . 8th . 9 the first electrode layer 4 have a thickness of 200 nm in this example, but various thicknesses are possible. For different materials and different structures, different advantageous minimum layer thicknesses can result, which is due to the different grain growth. In the present example, the anode is made of gold, although other oxidation-resistant materials are conceivable. The drift structure consists of indium tin oxide (ITO), the guard electrode of silver. Again, of course, other materials are conceivable.

Regarding the drift structure 7 It should be noted that for clarity only a few rings are shown here. Usually, the drift structures are much finer, so that, for example, between 10 and 100 drift rings are provided on one cm ² .

The Photoactive layer has a thickness of 200 nm above the first Electrode layer and consists of a semiconductor mixture PCBM and P3HT in a concentration ratio of 1: 1.

The cathode 10 consists of a semi-transparent layer sequence of 5 nm calcium and 15 nm silver. The thin calcium layer is actually the electrically functional layer, which is then protected by the subsequent silver layer effectively against oxidation, especially by water molecules, as long as the manufacturing process is not completed.

At It should be noted that all thickness specifications are obvious for example only and the figures are not for better illustration are true to scale.

The organic drift diode 1 has five outer terminals a, i, o, g, c for the anode, the innermost drift ring 14 , the outermost drift ring 15 , the guard electrode 9 and the cathode 10 on. These are at the bottom of the substrate 2 arranged and via vias 16 with the respective electrodes 8th . 14 . 15 . 9 . 10 connected. To connect the cathode 10 with the corresponding outer terminal c is the cathode 10 in 1 right side over the photoactive layer 5 down to the substratum 2 pulled where they with a contact pad 17 is in electrically conductive connection. From the contact pad 17 is over the via 16 the connection with the outer terminal c given. A wire bonding is therefore not required here.

2 shows a second embodiment of an organic drift diode 1' according to the first embodiment, wherein like parts are provided with the same reference numerals. The drift electrode 1' is different from the drift electrode 1 not by building up the layers 4 . 5 and 6 but by a different type of encapsulation and a different type of external connections. It can be seen that there is no effect on the second electrode layer 6 So the cathode 10 , Glued glass substrate provided, but it is to protect against environmental influences a thin layer 18 intended as encapsulation. In this case, it is made of silicon nitride, but other materials are conceivable.

The thin film 18 does not extend beyond the present case at the edge of the substrate 2 arranged, schematically illustrated outer terminals a, i, o, g and c. To connect between the corresponding electrodes 8th . 14 . 15 . 9 and 10 with the outer terminals in this case is directly on the substrate 2 a conductor track layer 19 arranged, the corresponding conductor tracks to the outer terminals a, i, o, g, c and contact pads for the electrodes comprises, which are not shown here for clarity reasons. In order to prevent electrical contact with the electrodes is between the interconnect layer and the layer assembly 3 a passivation layer 20 provided, which is structured such that a connection of the respective electrodes 8th . 14 . 15 . 9 . 10 is made possible with the corresponding contact pads. The conductor layer 19 and the passivation layer 20 thus form basic layers that serve to contact the electrodes.

An embodiment of an organic drift diode 1'' according to the second embodiment of the present invention is in 3 shown. Again, the same reference numerals are used for the same components. As in the first embodiment, a layer arrangement 3 from a first electrode layer 4 , a photoactive layer 5 and a second electrode layer 6 on a substrate 2 arranged. In contrast to the first embodiment, however, the first electrode layer comprises herein 4 the cathode 10 and the second electrode layer 6 includes the drift structure 7 and the anode 8th , A guard electrode is not provided in this example, but could of course also be present. As the light, as indicated by the arrows 12 represented, in this case by the substrate 2 and the first electrode layer 4 is done, is the substrate 2 formed as a glass substrate. However, it would also be conceivable to use, for example, a film. The cathode 10 again, is quite thin and semi-transparent, and in this case consists of ITO processed to obtain a low work function that is resistant to oxidation and sufficiently transparent. The cathode 10 again is quite thin, it has a thickness of about 60 nm. The electrodes 7 . 8th the second electrode layer 6 in this case have a thickness of 100 nm. In this case, the choice of material for the drift structure 7 and the anode 8th a wider choice, since there is no loss of quality in the production of oxidation-sensitive materials. It can be used here, for example, barium or calcium.

The four provided in this case four outer terminals a, i, o, c for the anode 8th , the innermost drift ring 14 , the outermost drift ring 15 and the cathode 10 are in turn at the edge of the substrate 2 arranged. The cathode 10 is formed correspondingly enlarged and connected directly to its associated external contact c. The remaining connections of the electrodes 8th . 14 and 15 with its associated contacts a, i, o is connected by wire bonding wires 21 realized.

To the drift diode 1'' including the wires 21 To protect against environmental influences, is also an encapsulation 22 provided, which consists of a thin-layer sequence in the example shown. This is in the enlarged range 23 in the area of a wire 21 shown more clearly. Thereafter, the layer structure comprises the encapsulation 22 an inner organic thin film 24 and an outer inorganic thin film 25 , The inner thin film 24 In the present example, epoxy is to form a flat surface for the second thin film 25 , which consists of SiNx.

The drift ring structure 7 does not have, as shown so far, concentric rings surrounding the circular anode 8th are arranged, but there are various geometric configurations are conceivable, which with recourse to the 4 - 12 now be shown in more detail.

4 shows the drift ring structure 7 , as according to the embodiments 1 - 3 is used. Therein is a plurality concentric around the circular electrode 8th arranged drift rings 26 intended. This is the well-known "classical" geometry.

5 shows a second embodiment in which the drift structure 7 through a single spiral electrode 27 is realized, which is around the central circular anode 8th extends. It is for the electrode 27 used a material with a higher resistance, so that when contacting at the inner edge 28 and at the outer edge 29 sets the desired potential distribution.

Another embodiment of a drift structure 7 is 6 refer to. There is an extended ring electrode 26 around the central circular anode 8th intended. In this case, the sheet resistance should be slightly higher than in the spiral structure.

Regarding the embodiment in 5 and 6 It should also be noted that in this case, the inner contact can be optionally saved if a direct connection to the anode 8th will be produced.

Another embodiment of a drift structure 7 shows 7 , where here the anode 8th annular the drift structure 7 surrounds. This again consists of concentric drift rings 26 surrounding a central drift electrode 30 are arranged.

The 8th and 9 show embodiments analogous to the 5 and 6 in which as well a the drift structure 7 surrounding annular anode 8th is provided.

If an arrangement of a plurality of inventive organic drift diodes in a nuclear medicine detector, in particular a SPECT detector, adjacent to be arranged, so offer to realize a better coverage polygonal structures. 10 now shows an arrangement 31 several organic drift diodes, as in a here only indicated SPECT detector 32 can be used. The central anode 8th is hexagonal, the drift structure 7 consists of several concentric, as hexagonal, the anode 8th surrounding corner electrodes 33 , In this way, the in 10 shown honeycomb structure, with which a good coverage is achieved can be realized.

Another embodiment of an arrangement 31 ' for a SPECT detector 32 ' is in 11 shown where in the drift diodes a square central anode 8th is provided by equally square frame electrodes 34 the drift structure 7 is surrounded. Thus, a structure can be made in the manner of individual pixels.

12 shows the embodiment of a drift structure 7 , via which a linear organic drift diode can be realized. Here are in the drift structure 7 several parallel stripe electrodes 35 provided, wherein the anode 8th as well as arranged parallel, adjacent strip electrode 36 is trained. In such a structure, position information from the drift structure may be perpendicular to the strip electrodes 35 be inferred.

To produce the organic drift diodes according to the present invention, it is necessary to distinguish between the first embodiment (drift diodes 1 . 1' ) and the second embodiment (drift diode 1'' ). Drift diodes according to the first embodiment are manufactured in a first method of manufacturing, drift diodes of the second embodiment according to a second method. Examples of both methods are detailed below.

In a variant of the first method are on a glass substrate of 0.7 mm thickness initially using sputtering techniques and lithographic patterning Tracks to four outer terminals (a, i, o, c) guided at the edge of the substrate. For this purpose can for example, a 400 nm thick aluminum layer can be used, For example, structuring methods from the LCD display technology can be used. These tracks and the corresponding ones Contact pads are used for electrical insulation through a passivation layer, For example, 200 nm SiNx from chemical vapor deposition, covered. The passivation layer is then lithographically structured, only the four inner contact pads and the corresponding outer Terminals a, i, o and c remain free at the substrate edge.

On the thus provided with basic layers substrate is through Sputtering applied a 200nm thick gold layer by lithographic Processes as anode and structured as a contact pad for the cathode becomes. In a next step, in turn, by sputtering with an oxide target, a 200 nm thick ITO layer and applied also lithographically structured as a drift structure. The drift structure and the anode accordingly now together form the first electrode layer.

Subsequently becomes an organic semiconductor mixture of PCBM and P3HT in the concentration ratio of 1: 1 from a total of 1% solution in xylene by spray coating in a layer thickness of 200 nm over the first electrode layer applied as a photoactive layer. It will be done with a shadow mask the substrate edge as well as the contact pad for the later Covered cathode covered. After that, the photoactive layer becomes annealed at 100 ° C for 15 minutes, leaving a partial separation of the mixture into a bi-continuous network achieved on sub-micron scale, which is favorable affects the extraction efficiency of the charge carriers.

Subsequently, by thermal evaporation at low deposition rates of 1 Å / sec. a semi-transparent layer of 5 nm of calcium and 15 nm of silver is applied as the cathode of the second electrode layer. In this case, in turn, a shadow mask is used, through which the cathode is also led down via the photoactive layer to the contact pad for the cathode. In a final step, the entire component is protected by the adhesion of another transparent glass substrate from the effects of oxygen and humidity. This further glass substrate is slightly smaller than the glass substrate serving as a carrier substrate, so that the outer aluminum terminals remain open for contacting the anode, the cathode and the innermost and outermost drift structure contacts.

In an embodiment of the second method Again, a 0.7 mm thick glass substrate is used. On this Glass substrate is first a 400 nm thick aluminum layer applied by sputtering and to external terminals on the Textured edge of the substrate. Then it goes through to the substrate thermal evaporation a semi-transparent layer of 20 nm ITO applied and to a cathode and to a compound of the cathode to the corresponding external connection by lithographic Structured techniques. The cathode forms the first electrode layer.

After that As in the first method, an organic semiconductor mixture made of PCBM and P3HT in a concentration ratio of 1: 1 1% solution in xylene by spray coating in one layer thickness of 200 nm applied. It will in turn be with a shadow mask the substrate edge as well as the outer connections and contact pads for the later to be applied Covered electrodes. The photoactive layer becomes as in the first method annealed for 15 min. at 100 ° C.

thereupon is by thermal evaporation using a shadow mask a 100 nm thick gold layer is applied as an anode structured. In a further step, in turn, by thermal evaporation a 100 nm thick ITO layer applied through a shadow mask is structured in the form of the drift structure.

Subsequently be the anode and the drift structure, the second electrode layer form, by wire bonding with the corresponding outer Terminals or associated with these contact pads connected. This takes place advantageously in inert gas instead of affecting the sensitive layers.

immediate after that, chemical vapor deposition processes become a first organic encapsulation layer of epoxy over the entire assembly including the bonding wires applied, leaving a relative smooth surface is formed. On this relatively smooth Surface is then in a second encapsulation step with similar methods a second encapsulation layer made of inorganic silicon nitride.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 2004/0159793 [0005]

Claims (55)

Organic drift diode with outer terminals (a, i, o, u, g), characterized in that it comprises a substrate ( 2 ) and one on the substrate ( 2 ) layer arrangement ( 3 ), wherein the layer arrangement ( 3 ) starting from the substrate-next layer, a first electrode layer ( 4 ), one adjacent to the first electrode layer ( 4 ) arranged photoactive layer ( 5 ) comprising an organic semiconductor mixture of an electron-transporting and a hole-transporting material and one adjacent to the photoactive layer ( 5 ) arranged second electrode layer ( 6 ), wherein one of the electrode layers ( 4 . 6 ) a drift structure ( 7 ) and a first type of electrode selected from the anode ( 8th ) or cathode ( 10 ), and the other electrode layer ( 6 . 4 ) comprises an extended second type of electrode chosen from the group of choices and does not correspond to the first type of electrode, and the entirety of the layers and optionally of the substrate ( 2 ) on at least one side of the photoactive layer ( 5 ) is at least semitransparent. Drift diode according to claim 1, characterized in that an outer anode terminal (a) for the anode ( 8th ), an outer cathode terminal (c) for the cathode ( 10 ) and two drift structure connections (i, o), in particular an innermost drift structure connection (i) and an outermost drift structure connection (o), for the drift structure ( 7 ) are provided. Drift diode according to claim 1 or 2, characterized in that the second electrode layer ( 6 ) comprises the second type of electrode. Drift diode according to claim 3, characterized in that the second electrode layer ( 6 ) is semitransparent. Drift diode according to claim 3 or 4, characterized in that the drift structure ( 7 ) and the first type of electrode consist of oxidation-resistant materials. Drift diode according to claim 1, characterized in that the first electrode layer ( 4 ) comprises the second type of electrode. Drift diode according to claim 6, characterized in that at least the substrate ( 2 ) and the first electrode layer ( 4 ) are designed at least semitransparent. Drift diode according to one of the preceding claims, characterized in that the outer terminals (a, c, i, o, g) on the said layer arrangement ( 3 ) facing away from the substrate ( 2 ) are provided and via vias ( 16 ) with the respective electrodes ( 8th . 10 . 14 . 15 . 9 ) are connected. Drift diode according to one of the preceding claims, characterized in that the electrode or the electrodes of the second electrode layer ( 6 ) are connected by wire bonding to the corresponding outer terminals (a, c, i, o, g). Drift diode according to one of the preceding claims, characterized in that the layer arrangement ( 3 ) the substrate ( 2 ) facing a conductor track layer ( 19 ) for connecting at least part of the electrodes to the corresponding ones on the substrate ( 2 ) provided outer terminals (a, c, i, o, g) and a passivation layer ( 20 ) for isolation from the remaining layers. Drift diode according to claim 10, characterized in that the second electrode layer ( 6 ) comprises the second type of electrode, which laterally to a corresponding contact pad ( 17 ) on the larger than the layer arrangement ( 3 ) dimensioned substrate ( 2 ) is extended. Drift diode according to one of the preceding claims, characterized in that the semiconductor mixture is a bi-continuous Bulk heterostructure is formed. Drift diode according to one of the preceding claims, characterized in that the electron transporting material C60, a C60 derivative or phenyl C61-butyric acid methyl ester is. Drift diode according to one of the preceding claims, characterized in that the hole transporting material Polyphenylenevinylene derivative, in particular MEH-PPV, or a substituted Thiophene, in particular poly-3-hexylthiophene or poly-3-octyltiophene, is. Drift diode according to one of the preceding claims, characterized in that the photoactive layer ( 5 ) has a thickness of 100 to 500 nm, in particular 200 nm. Drift diode according to one of the preceding claims, characterized in that the layer arrangement ( 3 ) between the photoactive layer ( 5 ) and the first and / or second electrode layer ( 4 . 6 ) comprises a further organic semiconductor layer, namely an electron-transporting or a hole-transporting transport layer. Drift diode according to one of the preceding claims, characterized in that the Ano de ( 8th ) consists of indium tin oxide, gold, silver, platinum, palladium or a mixture of these substances. Drift diode according to one of the preceding claims, characterized in that the cathode ( 10 ) consists of indium tin oxide, aluminum, magnesium, silver, calcium, an inorganic salt, in particular lithium fluoride, sodium fluoride or cesium fluoride, or a mixture of these substances. Drift diode according to one of the preceding claims, characterized in that the first type of electrode, the anode ( 8th ) and the drift structure ( 7 ) consists of indium tin oxide, aluminum, magnesium, silver, calcium, an inorganic salt, in particular lithium fluoride, sodium fluoride or cesium fluoride, or a mixture of these substances or that the first type of electrode is the cathode ( 10 ) and the drift structure ( 7 ) consists of indium tin oxide, gold, silver, platinum, palladium or a mixture of these substances. Drift diode according to one of the preceding claims, characterized in that the first type of electrode and the drift structure ( 7 ) consist of different materials. Drift diode according to one of the preceding claims, characterized in that the first type of electrode and / or the drift structure ( 7 ) has a thickness of 100 to 300 nm, in particular 200 nm. Drift diode according to one of the preceding claims, characterized in that the second type of electrode has a thickness from 10 to 30 nm, in particular 20 nm. Drift diode according to one of the preceding claims, characterized in that the substrate ( 2 ) consists of glass, ceramic or metal or a semiconductor wafer, a circuit board or a film, in particular a polymer film is. Drift diode according to one of the preceding claims, characterized in that the substrate ( 2 ) has a thickness of 0.5 to 1 mm, in particular 0.7 mm. Drift diode according to one of the preceding claims, characterized in that it comprises an encapsulation for protecting the layer arrangement ( 3 ). Drift diode according to claim 23, characterized in that the encapsulation a glass or metal substrate ( 11 ). Drift diode according to claim 25 or 26, characterized in that the encapsulation ( 22 ) at least one thin layer ( 18 . 24 . 25 ) of organic and / or inorganic material, in particular silicon nitride, silicon oxide, aluminum oxide, aluminum oxynitride, epoxy, parylene or polyacrylate. Drift diodes according to one of the preceding claims, characterized in that the drift structure ( 7 ) comprehensive electrode layer ( 4 . 6 ) additionally at least one guard electrode ( 9 ) for field degradation. Drift diode according to one of the preceding claims, characterized in that the drift structure ( 7 ) spaced, concentric ring electrodes ( 26 ) or polygonal electrodes ( 33 ) or an extended ring electrode ( 26 ) or polygonal electrode or circular electrode or square electrode or a spirally outwardly extending spiral electrode ( 27 ). Drift diode according to claim 29, characterized in that the first type of electrode in the center of the drift structure ( 7 ) is arranged. Drift diode according to claim 29, characterized in that the first type of electrode the drift structure ( 7 ) surrounds. Drift diode according to one of claims 1 to 28, characterized in that the drift structure ( 7 ) spaced apart, parallel strip electrodes ( 35 ) and the first type of electrode as being parallel to the strip electrodes ( 35 ) of the drift structure ( 7 ) extending strip electrode ( 36 ) and adjacent to an outer strip electrode ( 35 ) of the drift structure ( 7 ) is arranged. Drift diode according to one of the preceding claims, characterized in that the drift diode ( 1 . 1' . 1' ) a field effect transistor adjacent in particular to the first type of electrode ( 13 ) or amplifier. Drift diode according to claim 33, characterized in that the field effect transistor ( 13 ) is an organic, in the layer arrangement integrated field effect transistor. SPECT detector comprising at least one organic drift diode ( 1 . 1' . 1'' ) according to one of the preceding claims. Method for producing an organic drift diode, in particular according to one of claims 1 to 35, characterized in that the following steps are provided: a) structured to a first electrode structure Depositing a first layer of a first material with little or no tendency to oxidation onto a substrate or a substrate provided with at least one basic layer; and patterning a second layer of a second material having little or no tendency to oxidize onto the substrate, structured to a second electrode structure; one electrode structure is a drift ring structure and the other electrode structure is a first type of electrode selected from the anode or cathode selection group and both electrode structures form a first electrode layer, b) application of a photoactive layer of an organic semiconductor mixture of an electron-transporting and a hole-transporting material from solution or by thermal Vaporizing the first electrode layer, wherein, in particular, regions of the substrate lying outside the first electrode layer are covered by a shadow mask, c) applying a second one Electrode layer as a second type of electrode, which is selected from the selection group and does not correspond to the first type of electrode, from a third material on the photoactive layer, in particular by physical vapor deposition. Method according to Claim 36, characterized the structuring in step a) takes place after the application, wherein a particular lithographic structuring of the first Material to the first electrode structure and one in particular lithographic structuring of the second material to the second Electrode structure is done. Method according to Claim 36, characterized that the structured application in step a) by means of a Shadow mask done. Method according to one of claims 36 to 38, characterized in that for the second electrode layer an at least semi-transparent material is used. Method for producing an organic drift diode, in particular according to one of claims 1 to 35, characterized characterized in that the following steps are provided: a) Applying a first electrode layer of a material with little or no tendency to oxidation as the first type of electrode, selected from the selection group anode or cathode, on Substrate or provided with at least one basic layer substrate b) applying a photoactive layer of an organic Semiconductor mixture of an electron transporting and a hole transporting material from solution or by thermal Evaporating on the first electrode layer, in particular outside The first electrode layer lying through areas of the substrate a shadow mask are covered, c) By means of a shadow mask or a printing process to a first electrode structure structured Applying a first layer to the photoactive layer and means a shadow mask or a printing process to a second electrode structure patterned application of a second layer to the photoactive layer by physical vapor deposition, wherein the one electrode structure a drift structure and the other electrode structure a second Type of electrode selected from the group of choices and not corresponds to the first type of electrode is, and both electrode structures a form second electrode layer. Method according to claim 40, characterized in that in that an at least semitransparent substrate, in particular glass, and a semitrans parent material for the first electrode layer be used. Method according to one of claims 36 to 41, characterized in that the first electrode layer through physical vapor deposition, in particular by sputtering, is applied. Method according to one of claims 36 to 43, characterized in that the photoactive layer by spray coating is applied. Method according to claim 43, characterized in that that the semiconductor mixture of particular 1% solution is applied in xylene. Method according to one of claims 36 to 44, characterized in that between steps b) and c) a Annealing, in particular for 15 minutes at 100 ° C, the photoactive layer is performed. Method according to one of claims 36 to 45, characterized in that the application of the second electrode layer at low deposition rates, in particular at about 1 Å / s, is carried out. Method according to one of claims 36 to 46, characterized in that prior to step a) vias of the substrate for connecting the electrodes to outer Connections on the side facing away from the layers of the Substrate are created. Method according to one of claims 36 to 47, characterized in that before step a) a conductor track layer with structured tracks and contact pads and a structured passivation layer are applied, the grund forming laying layers. Method according to claim 48, characterized that for applying the basic layers first by physical vapor deposition, in particular by sputtering conductive material applied to the substrate and then in particular lithographically structured, after which a passivation material by physical vapor deposition, in particular by sputtering, is applied and in particular lithographically structured, so that the contact pads are not covered by the passivation layer are. Method according to one of claims 36 to 49, characterized in that the electrode or the electrodes of second electrode layer by wire bonding, in particular under Inert gas flow, with external connections get connected. Method according to one of claims 36 to 50, characterized in that an encapsulation for protecting the layers is attached. Process according to claim 51, characterized in that a glass substrate and / or a ceramic substrate on the second Electrode layer is adhered. A method according to claim 51 or 52, characterized that as encapsulation a thin layer or layer sequence of organic and / or inorganic material, in particular silicon nitride, Silica, alumina, aluminum oxynitride, epoxy, parylene or polyacrylate. Method according to one of claims 36 to 53, characterized in that during the application of the layers of the Drift structure comprehensive electrode layer a third as a guard electrode or Guarde electrodes structured layer as part of the electrode layer is applied. Method according to one of claims 36 to 54, characterized in that in particular in the basic layers integrated a particular organic field effect transistor applied or is attached.