HK1140311B - Active matrix optical device - Google Patents

Description

Active matrix optical device

Technical Field

The present invention relates to active matrix optical devices. Embodiments of the present invention relate to methods of depositing organic thin film transistors and optically active pixels on a common substrate to form active matrix devices, in particular active matrix organic light emitting devices.

Background

Transistors can be divided into two main types: bipolar junction transistors and field effect transistors. Both types share a common structure comprising three electrodes between which a semiconductor material is arranged in the channel region. The three electrodes of a bipolar transistor are called the emitter, collector and base, while in a field effect transistor the three electrodes are called the source, drain and gate. Bipolar junction transistors can be described as current-operated devices because the current between the emitter and collector is controlled by the current flowing between the base and emitter. In contrast, a field effect transistor may be described as a voltage operated device, since the current flowing between the source and drain is controlled by the voltage between the gate and the source.

Transistors can also be classified as p-type and n-type according to whether they include a semiconductor material that conducts positive charge carriers (holes) or negative charge carriers (electrons), respectively. The semiconductor material may be selected based on its ability to accept, conduct, and donate (donate) charges. The ability of a semiconductor material to accept, conduct, and donate holes or electrons may be enhanced by doping the material. The materials used for the source and drain electrodes may also be selected according to their ability to accept and inject holes or electrons.

For example, a p-type transistor can be formed by selecting a semiconductor material that is efficient at accepting, conducting, and donating holes and selecting materials for the source and drain electrodes that are efficient at injecting and accepting holes from the semiconductor material. Good energy-level matching of the fermi level in the electrode with the HOMO level of the semiconductor material can enhance hole injection and acceptance. In contrast, an n-type transistor device can be formed by selecting a material that is efficient at accepting, conducting, and donating electrons and selecting a material for the source and drain electrodes that is efficient at injecting electrons into and accepting electrons from the semiconductor material. Good energy-level matching of the fermi level in the electrode with the LOMO level of the semiconductor material can enhance electron injection and acceptance.

The transistor may be formed by depositing elements in a thin film to form a Thin Film Transistor (TFT). When an organic material is used as the semiconductor material in such devices, it is referred to as an Organic Thin Film Transistor (OTFT). OTFTs can be manufactured by low-cost, low-temperature methods such as solution processing. Furthermore, OTFTs are compatible with flexible plastic substrates, which may offer the prospect of mass production of OTFTs on flexible substrates in a roll-to-roll process.

Various arrangements of organic thin film transistors are known. One such device is an insulated gate field effect transistor which includes source and drain electrodes with a semiconductor material disposed therebetween in a channel region, a gate electrode disposed adjacent to the semiconductor material, and a layer of insulating material disposed between the gate electrode and the semiconductor material in the channel region.

One use of transistors is in active matrix optical devices such as light detecting and emitting devices, particularly organic light emitting devices and organic photodetector arrays. For example, an active matrix organic light emitting display includes a matrix of organic light emitting devices forming the pixels of the display. Each organic light emitting device includes an anode, a cathode, and an organic light emitting layer disposed therebetween. In operation, holes are injected into the device through the anode and electrons are injected into the device through the cathode. The holes and electrons combine in the organic light-emitting layer to form an exciton which then undergoes radiative decay to give light (in a light-detecting device this process essentially goes in reverse). Other layers may also be provided between the electrodes to enhance charge injection and transport, such as hole injection layers, electron injection layers, hole transport layers, and/or electron transport layers. Mixtures of materials may also be used to enhance operation, such as mixtures of charge transport and emissive materials. Organic photoresponsive devices comprise the same structure of organic layers between two electrodes and can in fact be considered as organic light-emitting devices that operate in reverse (i.e. generate holes and electrons and separate when the device is exposed to light).

A pixel of an active matrix organic light emitting display may be switched between an emissive state and a non-emissive state by varying the current flowing through the pixel using a storage element, typically comprising a storage capacitor and two transistors, one of which is a drive transistor.

It is known to use a common substrate for thin film transistors and organic light emitting devices to form active matrix organic light emitting displays. For example, US 6150668 discloses depositing an Organic Thin Film Transistor (OTFT) and an Organic Light Emitting Device (OLED) on a common substrate and using the same material layer for both the OTFT gate and the OLED anode. The OLED cathode is selectively deposited through a shadow mask. Furthermore, US 692450 discloses depositing an OTFT and an OLED on a common substrate and using the same material layer for the source and drain electrodes of the OTFT and the anode of the OLED. This document also discloses forming the top gate of the OTFT and the cathode of the OLED in one step by depositing a metal over the entire surface and then patterning this layer to form the top gate and the cathode.

In view of the above, it is clear that in prior art monolithically integrated OLED/OTFT constructions, certain layers in the OLED and OTFT must be selectively deposited and patterned by post-deposition processing. For example, separate structures are provided to contain the organic semiconductor material of the OTFT and the organic light emitting material of the OLED. Furthermore, in prior art arrangements, the cathode of the OLED and the gate of the OTFT have been selectively deposited or patterned by post-deposition processing in order to prevent electrical shorts between the OTFT and OLED on the top surface of the device.

It is an aim of certain embodiments of the present invention to provide a method of manufacturing an active matrix organic light emitting display comprising thin film transistors and organic light emitting devices deposited on a common substrate which is simpler and faster than prior art arrangements, thus saving time and cost in the display manufacturing process.

It is a further object of certain embodiments of the present invention to reduce the processing steps involved in such methods and to fabricate new structures for active matrix organic light emitting displays comprising thin film transistors and organic light emitting devices deposited on a common substrate.

It is a further object of some embodiments of the present invention to provide alternative methods and structures for isolating thin film transistors deposited on a common substrate from organic light emitting devices in an active matrix organic light emitting display to prevent electrical shorts between the thin film transistors and the organic light emitting devices.

It is a further object of some embodiments of the present invention to provide alternative methods and structures for packaging thin film transistors and organic light emitting devices together deposited on a common substrate in an active matrix organic light emitting display.

Disclosure of Invention

An active matrix organic optical device comprising a plurality of organic thin film transistors and a plurality of pixels deposited on a common substrate, wherein the organic thin film transistors and pixels are provided with a common bank layer defining a plurality of wells, wherein some of the wells contain organic semiconductor material of the organic thin film transistors therein and others of the wells contain organic optically active material of the pixels therein.

The optical device may be an organic photoresponsive device (e.g. a photodetector) or an organic light-emitting device (e.g. an organic light-emitting display). Preferably, the device is an organic light emitting device, in which case the organic optically active material is an organic light emitting material.

A pixel circuit is formed by each pixel and its associated organic thin film transistor, together with any additional drive elements. For example, each pixel circuit in an active matrix organic light emitting device will typically comprise a light emitting pixel diode; an associated organic thin film transistor serving as a driving transistor; a switching thin film transistor; and a capacitor.

According to a second aspect of the present invention there is provided a method of manufacturing an active matrix organic optical device comprising forming a plurality of organic thin film transistors and a plurality of pixels on a common substrate, wherein a common bank layer is provided for the organic thin film transistors and the pixels, the bank layer defining a plurality of wells, wherein some of the wells contain organic semiconductor material of the organic thin film transistors therein and others of the wells contain organic optically active material of the pixels therein.

According to the first and second aspects of the invention, a common bank structure is provided in an active matrix organic optical device for both the organic semiconductor material of the organic thin film transistor and the organic optically active material of the pixel. The common bank structure provides a quick and easy method for isolating the OTFTs and the pixel structures when they are deposited on a common substrate.

According to a third aspect of the present invention there is provided a method of forming an active matrix organic optical device comprising: a plurality of thin film transistors and a plurality of organic optically active pixels are deposited on a common substrate, wherein insulating separation structures are provided to electrically isolate the thin film transistors from the organic optically active pixels on a top surface of the active matrix organic optical device.

According to a fourth aspect of the present invention there is provided an active matrix organic optical device comprising: a plurality of thin film transistors and a plurality of organic optically active pixels on a common substrate, wherein an insulating separating structure is provided to electrically isolate the thin film transistors from the organic optically active pixels on a top surface of the active matrix organic optical device.

According to third and fourth aspects of the invention, insulating separation structures are provided to electrically isolate the thin film transistors from the pixels on the top surface of the active matrix organic optical device. With this arrangement, there is no need to selectively deposit or pattern the top electrode material of at least one of the pixels and thin film transistors by post-deposition processing as in prior art arrangements. To this end, the insulating separation structure is provided before the deposition of the top electrode layer.

In one arrangement, the insulating separation structure is provided as a raised ring around the thin film transistor such that the top electrode material of the thin film transistor is electrically isolated from the top electrode material of the pixel. The ring may be formed by photolithography and may have an undercut structure (i.e., the thickness of the ring wall is widest at or near its upper surface).

The top electrode may be formed of one or more layers, for example, the top electrode of a pixel may be a cathode including an aluminum single layer or a barium and aluminum double layer. In the case of an organic light emitting device, the top electrode of the organic light emitting pixel is preferably the cathode, however, for a so-called "inverted" device in which the pixels are constructed in the order cathode-organic light emitting material-anode, it may be the anode.

In another arrangement, the insulating separating structure comprises a layer of insulating material over the thin film transistor so as to electrically isolate the thin film transistor from the top electrode material of the pixel.

In yet another arrangement, a combination of an insulating ring separation structure around the thin film transistor and a layer of insulating material over the thin film transistor is provided.

The insulating separating structure may be provided in addition to the manner of the common bank structure described in relation to the first and second aspects of the invention. For example, a raised ring structure may be provided on top of the bank structure around the thin film transistor.

The top electrodes of both the thin film transistor and the pixel may be formed by depositing a common material, so that separate deposition and patterning of the top electrodes for the thin film transistor and the organic light emitting pixel may be avoided. As described in relation to the third and fourth aspects of the invention, the top electrode material may be blanket deposited over the entire active area of the display, with the insulating separating structure electrically isolating the thin film transistors from the top electrodes of the organic light emitting pixels. That is, the top electrodes of the thin film transistors and the organic light emitting pixels may be formed in a single deposition step.

Drawings

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

figure 1 shows a portion of an active matrix organic light emitting display according to an embodiment of the present invention;

figure 2 shows a portion of an active matrix organic light emitting display according to another embodiment of the present invention;

FIG. 3 illustrates the steps involved in forming an active matrix organic light emitting display according to the embodiment shown in FIG. 1;

fig. 4 shows a plan view illustrating separation of an organic thin film transistor and an organic light emitting device according to an embodiment of the present invention;

FIG. 5 shows a plan view illustrating an active matrix organic light emitting display including a plurality of electrode separation structures of the type shown in FIG. 4;

fig. 6 shows a plan view illustrating an active matrix organic light emitting display including a plurality of electrode separating structures according to another embodiment;

figure 7 shows a portion of an active matrix organic light emitting display including a top gate thin film transistor according to an embodiment of the present invention; and

fig. 8 shows a portion of an active matrix organic light emitting display including a common cathode and gate electrode with a channel hole connecting the gate electrodes according to another embodiment of the present invention.

Detailed Description

Fig. 1 shows a portion of an active matrix organic light emitting display according to an embodiment of the present invention. The figure shows an Organic Light Emitting Device (OLED) deposited on the right side of the substrate and an Organic Thin Film Transistor (OTFT) deposited on the left side of the substrate for driving the OLET.

The OTFT is a bottom gate type and includes: a gate electrode 2; a gate dielectric layer 4; source and drain electrodes 6, 8; and a layer of organic semiconductor material 10.

The OLED includes: an anode 20; a hole injection layer 22; a hole transport layer 24; an organic light-emitting layer 26; and a cathode 28.

The common bank structure 30 provides a well into which at least some layers of the OLED and OTFT are deposited.

A separation ring 32 is provided on top of the bank structure 30 around the OTFT. The separating ring 32 isolates the OTFTs from the OLEDs so that the cathode material of the OLEDs can be blanket deposited over the active area of the display without shorting the OLEDs and OTFTs across the top of the device. That is, the separating ring separates the cathode material deposited on the OLED from the cathode material deposited on the OTFT. The separating ring advantageously has an undercut (under-cut) structure to enhance the electrical isolation of the OLED from the OTFT.

The above arrangement is advantageous because for active matrix organic light emitting displays, the cathode of the OLED, which may be a PLED (polymer light emitting device) or a SMOLED (small molecule organic light emitting device), is typically deposited over the entire active surface of the display. This is because, for an active matrix OLED display, each OLED sub-pixel has a common cathode connection and is selected by controlling the anode connection.

One problem with bottom-emitting active matrix OLED displays is that the OTFTs and OLEDs are deposited side-by-side on the same substrate. For a bottom gate display, the organic semiconductor of the OTFT is exposed on the surface and will be in contact with the cathode. By using the techniques disclosed herein, a cathode separator ring around the OTFT electrically isolates the cathode metal covering the OTFT from the cathode of the OLED. At the same time, the metal covering the OTFT acts as the primary encapsulant.

As an alternative to the cathode separator ring structure described above, a layer of insulating material may be provided over the OTFT prior to deposition of the cathode material of the OLED. It may be desirable to use such insulating layers to protect/passivate the OTFT from the cathode, to prevent shorting of the cathode to the source and drain electrodes in the event of exposure of the metal regions due to incomplete organic semiconductor coverage, and to prevent channel shorting effects. This can be achieved by depositing an organic insulating film on top of the OTFT prior to cathode deposition.

In one arrangement shown in fig. 2, the two alternatives discussed above are combined. That is, both the separating ring and the insulating layer 34 (organic passivation material) are provided to further protect and isolate the OTFT from the electrical, physical, and chemical properties of the cathode. For example, if the organic semiconductor material is deposited from solution, the effects associated with solvent evaporation may cause the resulting thin film 19 to be thinner at its periphery than at its center. In this case, the insulating layer 34 serves to prevent the cathode material layer covering the organic thin film transistor from contacting the source and/or drain electrodes 6, 8. The other elements in fig. 2 are the same as those shown in fig. 1 except that an insulating layer is added over the organic semiconductor material in the TFT, and are therefore not re-numbered for clarity.

A preferred solution here would be to deposit the passivation material for the insulating layer 34 by inkjet printing on top of the organic semiconductor material. Such ink-jettable passivation materials are preferably organic. In order to avoid the passivating ink causing re-dissolution of the organic semiconductor material, one of two approaches can be utilized: (1) crosslinking the organic semiconducting material to allow the use of a wide range of passivating solvents; or (2) ink-jet printing from an orthogonal solvent. Note that in the latter approach, the organic semiconductor material is typically soluble in non-polar solvents, while the passivation material is typically soluble in polar solvents (methanol, ethanol, water, PGMEA (propylene glycol methyl ether acetate)). Typical materials used as organic passivation materials include PVA (polyvinyl acetate), PMMA (polymethyl methacrylate) and PVP (polyvinyl phenol).

FIG. 3 illustrates one method of implementing the present invention in an OTFT-PLED display. A back plane (backplane) was constructed in the following steps (a schematic cross-sectional view is shown):

1. gate 2 and PLED anode 20 deposition and patterning (e.g., patterning of ITO coated substrates);

2. dielectric deposition and patterning 4 (e.g., cross-linkable, photo-patternable dielectrics);

3. source-drain material deposition and patterning 6, 8 (e.g. gold, photolithography);

4. bank deposition and patterning 30;

5. cathode separator deposition and patterning 32;

6. organic layer deposition, for example by inkjet printing (OTFT: organic semiconductor 10; OLED: hole injection layer 22, hole transport layer 24, light emitting polymer 26); and

7. and cathode deposition 28.

The organic layer of fig. 3 is entirely contained within the well. While this is preferred, it should be recognized that it is not required. For example, the light emitting polymer may be deposited in such a way that the layer 26 extends beyond the perimeter of the well but still the emissive area of the pixel is defined by the boundaries of the well. Likewise, other layers of the pixel may extend beyond the boundary of the well (in practice this is preferred for the cathode of the emissive pixel) but the light emission and light detection regions of the pixel are still defined by the well boundary.

The cathode separator breaks the electrical continuity between the cathode metal covering the OTFT and the metal area covering the OLED.

Fig. 4 shows a plan view illustrating separation of an organic thin film transistor from an organic light emitting device. The plan view shows that the separators (shown in cross-section in the previously discussed figures) are annular in nature to provide isolation of the metal covering the OTFT. The cathode separator ring surrounds the region of the OTFT where the organic semiconductor material 10 is located. The organic semiconductor material in the embodiment of fig. 4 is contained in two wells: the materials in the two wells together form part of a single OTFT. The use of multiple wells as shown in figure 4 is advantageous in that the well dimensions may be selected to ensure good well filling when printing organic semiconductor material into the wells, however, it causes an increase in the area of the OTFT due to the inactive regions of the bank material between the wells, which in turn reduces the percentage of area of the substrate that can be used for the emitter pixel. Thus, in one alternative arrangement, the organic semiconductor material is contained in a single large well in order to minimise the area of the OTFT.

Fig. 5 shows a plan view illustrating an active matrix organic light emitting display including a plurality of electrode separation structures of the type shown in fig. 4. Since only discrete areas of the cathode are "cut away" from the cathode face, electrical continuity across the panel is maintained.

Fig. 6 shows a plan view illustrating an active matrix organic light emitting display including a plurality of electrode separation structures according to another embodiment. In such an arrangement, a cathode separator ring has been incorporated into the line across the display. This arrangement separates the cathode into columns, as in a passive matrix display. In this case, these lines would need to be connected at the edge of the display. In fig. 6, it can be seen that the cathode columns are connected along the bottom region of the display as shown to form a common cathode across the display.

Fig. 7 shows another embodiment including a top-gate thin film transistor. The same reference numerals have been used for similar components as in the bottom gate TFT shown in figure 1. In the top-gate arrangement, the OLED has the same structure as that shown in figure 1, but the structure of the TFT is actually reversed, so that the source and drain electrodes 6, 8 are deposited on the substrate. A common bank structure 30 is deposited to form a well and organic semiconductor material 10 is deposited in the well over the source and drain electrodes. The gate dielectric 4 and gate electrode 2 are then deposited to complete the TFT.

In the embodiment shown in fig. 7, a layer of insulating material 44 is deposited over the gate electrode 2 in order to isolate the gate electrode 2 from the overlying cathode material 28 of the OLED. The insulating material 44 may be the same material as used for the organic passivation layer 34 in fig. 2. Alternatively, different materials may be selected because in this arrangement the gate dielectric and gate electrode provide some protection for the underlying organic semiconductor material, and as a result a greater range of materials may be selected for layer 44 than for layer 34 in fig. 2.

Fig. 8 shows another embodiment including a common electrode and gate material 28. In this arrangement, no insulating layer is required, as the cathode material 28 of the OLED also functions as the gate electrode of the TFT. Further, common reference numerals have been used as in the previously discussed figures for common components.

In the arrangement shown in fig. 8, an additional via contact 50 for connecting the gate electrode to a conductive connection line 52 is shown.

Accordingly, embodiments of the present invention may include top-gate or bottom-gate thin film transistors. The top electrode material can be deposited over the entire active area of the display, with the insulating separation structure preventing shorting between the TFT and the OLED. Embodiments of the invention allow the manufacture of bottom-emitting active matrix displays with a common self-shadowing cathode covering the entire display surface. The separated cathode provides the primary encapsulation for the OTFT. The use of an organic passivation material in combination with the cathode separator further improves the isolation of the OTFT from the cathode and suppresses short circuit effects. The use of a common bank structure allows both the TFT and the OLED to be easily fabricated on a common substrate.

Further details of suitable materials and processes for manufacturing a device according to the invention are set out below:

substrate

The substrate may be rigid or flexible. The rigid substrate may be selected from glass or silicon, and the flexible substrate may comprise thin glass or plastic, such as polyethylene terephthalate (PET), polyethylene naphthalate PEN, polycarbonate, and polyimide.

The organic semiconductor material may be made solution processable by the use of a suitable solvent. Exemplary solvents include mono-or polyalkylbenzenes (such as toluene and xylene); tetralin; and chloroform. Preferred solution deposition techniques include spin coating and ink jet printing. Other solution deposition techniques include dip coating, roll printing, and screen printing.

Organic semiconductor material

Preferred organic semiconductor materials include small molecules (such as optionally substituted pentacene); optionally substituted polymers (such as polyaromatics, in particular polyfluorenes and polythiophenes); and an oligomer. Mixtures of materials may be used, including mixtures of different material types (e.g., polymer and small molecule mixtures).

Source and drain electrodes

For a p-channel OTFT, it is preferred that the source and drain electrodes comprise a high work function material, preferably a metal having a work function greater than 3.5eV, such as gold, platinum, palladium, molybdenum, tungsten, or chromium. More preferably, the metal has a work function in the range of 4.5 to 5.5 eV. Other suitable compounds, alloys and oxides, such as molybdenum trioxide and indium tin oxide, may also be used. The source and drain electrodes may be deposited by thermal evaporation and patterned using standard photolithography and lift-off techniques well known in the art.

Alternatively, conductive polymers may be deposited as the source and drain electrodes. An example of such a conductive polymer is polyethylene dioxythiophene (PEDOT), although other conductive polymers are also known in the art. Such conductive polymers may be deposited from solution using, for example, spin-on or inkjet printing techniques, as well as other solution deposition techniques discussed above.

For an n-channel OTFT, preferably, the source and drain electrodes comprise materials such as, for example, a thin layer of a metal or metal compound such as calcium or barium having a work function of less than 3.5eV, in particular, oxides or fluorides of basic or alkaline earth metals such as lithium fluoride, barium fluoride and barium oxide. Alternatively, conductive polymers may be deposited as the source and drain electrodes.

For ease of manufacture, the source and drain electrodes are preferably formed of the same material. However, it will be appreciated that the source and drain electrodes may be formed of different materials in order to optimize charge injection and extraction, respectively.

The channel length defined between the source and drain electrodes may be up to 500 microns, but preferably the length is less than 200 microns, more preferably less than 100 microns, most preferably less than 20 microns.

Gate electrode

The gate electrode 4 may be selected from a wide range of conductive materials, such as metals (e.g. gold) or metal compounds (e.g. indium tin oxide). Alternatively, a conductive polymer may be deposited as the gate electrode 4. Such conductive polymers may be deposited from solution using, for example, spin-on or inkjet printing techniques, as well as other solution deposition techniques discussed above.

For example, the gate electrode, source electrode and drain electrode may be about 5 to 200nm thick, although typically 50nm as measured by Atomic Force Microscopy (AFM), for example.

Insulating layer

The insulating layer comprises a dielectric material selected from insulating materials having a high resistivity. The dielectric constant k of the dielectric is typically about 2-3, although materials with high k values are desirable because the achievable capacitance for OTFTs is proportional to k and the drain current I_DProportional to the capacitance. Therefore, to achieve high drain currents with low operating voltages, OTFTs with thin dielectric layers in the channel region are preferred.

The dielectric material may be organic or inorganic. Preferred inorganic materials include SiO2, SiNx, and spin-on glass (SOG). Preferred organic materials are typically polymers and include insulating polymers such as polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), acrylates such as Polymethylmethacrylate (PMMA) and benzocyclobutene (BCB) available from DowComing. The insulating layer may be formed of a material mixture or include a multilayer structure.

The dielectric material may be deposited by thermal evaporation, vacuum treatment or lamination techniques known in the art. Alternatively, the dielectric material may be deposited from solution using, for example, spin-on or inkjet printing techniques, as well as other solution deposition techniques discussed above.

If the dielectric material is deposited from solution onto the organic semiconductor, it should not cause dissolution of the organic semiconductor. Likewise, if the organic semiconductor is deposited onto the dielectric material from solution, the dielectric material should not dissolve. Techniques to avoid such dissolution include: using orthogonal solvents, i.e. using a solvent for depositing the uppermost layer that does not dissolve the underlying layer; and crosslinking of the underlying layers.

The thickness of the insulating layer is preferably less than 2 microns, more preferably less than 500 nm.

Other layers

Other layers may be included in the device architecture. For example, a self-assembled monolayer (SAM) may be deposited on the gate, source or drain electrodes, substrate, insulating layer and organic semiconductor material to promote crystallization, reduce contact resistance, repair surface characteristics and promote adhesion as desired. In particular, the dielectric surface in the channel region, in particular for a high-k dielectric surface, is provided with a monolayer comprising a binding region and an organic region in order to improve device performance, for example by improving the morphology (in particular polymer orientation or crystallinity) of the organic semiconductor and covering the charge traps. Exemplary materials for such monolayers include chloro silanes or alkoxy silanes with long alkyl chains, such as octadecyltrichlorosilane.

While the present invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (16)

1. An active matrix organic optical device comprising a plurality of organic thin film transistors comprising organic semiconductor material and a plurality of pixels comprising organic optically active material disposed on a common substrate, wherein a common bank layer is provided for the organic thin film transistors and the pixels, the common bank layer defining a plurality of wells, some of which contain the organic semiconductor material of the organic thin film transistors therein and others of which contain the organic optically active material of the pixels therein.

2. An active matrix organic optical device according to claim 1, wherein an electrode layer is provided on the common substrate, the common bank layer is provided over the electrode layer, and the organic semiconductor material of the organic thin film transistor and the organic optically active material of the pixel are provided within the well of the common bank layer.

3. An active matrix organic optical device according to claim 2, wherein the organic thin film transistor is a bottom gate thin film transistor.

4. An active matrix organic optical device according to claim 3, wherein the electrode layer comprises a gate electrode of each organic thin film transistor, each organic thin film transistor comprising a gate dielectric layer disposed over the gate electrode, and source and drain electrodes disposed over the gate dielectric layer, wherein the common bank layer is disposed over the source and drain electrodes and the organic semiconductor material is disposed in a channel region between the source and drain electrodes.

5. An active matrix organic optical device according to claim 2, wherein the organic thin film transistor is a top gate thin film transistor.

6. An active matrix organic optical device according to claim 5, wherein the electrode layer comprises a source electrode and a drain electrode of each organic thin film transistor, the common bank layer being disposed over the source and drain electrodes, each organic thin film transistor comprising an organic semiconductor material disposed in a channel region between the source and drain electrodes, a gate dielectric layer disposed on the organic semiconductor material, and a gate electrode disposed over the gate dielectric layer.

7. An active matrix organic optical device according to any of claims 1 to 6, further comprising an insulating layer disposed over each thin film transistor.

8. An active matrix organic optical device according to any one of claims 1 to 6, wherein a top electrode layer is provided over the entire active surface of the active matrix organic optical device, and insulating separation structures are provided to electrically isolate the thin film transistors from the pixels on the top surface of the active matrix organic optical device.

9. An active matrix organic optical device according to claim 8, wherein the insulating separation structures are provided as raised rings on the bank layer around the thin film transistors.

10. An active matrix organic optical device according to claim 9, wherein the raised ring has an undercut wall structure.

11. An active matrix organic optical device according to claim 8, wherein the top electrode layer forms both the top electrode of each organic thin film transistor and the top electrode of each pixel.

12. An active matrix organic optical device according to any one of claims 9 to 10, wherein the top electrode layer forms both the top electrode of each organic thin film transistor and the top electrode of each pixel.

13. A method of manufacturing an active matrix organic optical device comprising forming a plurality of organic thin film transistors and a plurality of pixels on a common substrate, wherein a common bank layer is provided for the organic thin film transistors and the pixels, the common bank layer defining a plurality of wells, wherein some of the wells contain organic semiconductor material of the organic thin film transistors therein and others of the wells contain organic optically active material of the pixels therein.

14. An active matrix organic optical device comprising: a plurality of thin film transistors and a plurality of organic optically active pixels on a common substrate, wherein an insulating separating structure is provided to electrically isolate the thin film transistors from the organic optically active pixels on a top surface of the active matrix organic optical device.

15. A method of forming an active matrix organic optical device, comprising: depositing a plurality of thin film transistors and a plurality of organic optically active pixels on a common substrate, wherein an insulating separating structure is provided to electrically isolate the thin film transistors from the organic optically active pixels on a top surface of the active matrix organic optical device.

16. The method of claim 15, wherein the thin film transistor and the organic optically active pixel have top electrodes formed of a common material in a single deposition step.