Patent Description:
The present disclosure is related to light emitting device, especially to an organic light emitting device and manufacturing method thereof.

Organic light emitting display (OLED) has been used widely in most high end electron devices. However, due to the constraint of current technology, the pixel definition is realized by coating a light emitting material on a substrate through a mask, and often, the critical dimension on the mask can not be smaller than <NUM> microns. Therefore, pixel density having <NUM> ppi or higher becomes a difficult task for an OLED maker.

<CIT> relates to a method for manufacturing an electroluminescence element that has a light emitting layer containing a quantum dot and exhibits excellent life characteristics.

<CIT> relates to an organic light-emitting display apparatus, including a pixel electrode, a pixel definition layer covering at least a portion of an edge of the pixel electrode, an emission layer on the pixel electrode, and a first intermediate layer on the pixel electrode and the pixel definition layer.

<CIT>relates to a display device that may include a first electrode, an organic light emitting layer positioned on the first electrode, a second electrode positioned on the organic light emitting layer, and an electron transport layer interposed between the organic light emitting layer and the second electrode, and including an electron transport material and an electron injection material.

<CIT> relates to an organic EL device including a substrate, a bank layer having therewithin an opening having an elongated shape in plan view, and a functional layer including an organic material, disposed within the opening, and having an elongated shape in plan view.

In the present disclosure, the light emitting units are formed by a photo sensitive material. The photo sensitive material is directly disposed on a substrate without through a mask. The pixel definition is realized by a photolithography process.

A light emitting device includes a first type carrier transportation layer and an organic light emitting unit over the first type carrier transportation layer. The light emitting device further includes a second type carrier transportation layer over the organic light emitting unit, wherein the second type is opposite to the first type. At least one of the first type carrier transportation layer and the second type carrier transportation layer includes a metal element.

In some embodiments, the metal element is a transition metal. The organic light emitting unit has a width being not greater than <NUM>. The organic light emitting unit is photo sensitive. The organic light emitting unit includes a footing extended laterally from the bottom of the organic light emitting unit. The organic light emitting unit includes a tapered sidewall and the tapered sidewall includes at least two different slopes.

A light emitting device includes a substrate and an array of organic light emitting units over the substrate. The light emitting device further has a secondary light emitting unit adjacent to one of the organic light emitting units in the array, wherein the secondary light emitting unit includes a second height and the one of the organic light emitting units in the array includes a first height, the second height is smaller than the first height.

In some embodiments, the light emitting device further includes a first type carrier transportation layer under the array of organic light emitting units and the secondary light emitting unit. The organic light emitting units in the array has a gap with an aspect ratio, wherein the aspect ratio is correlated to a height ratio between the secondary light emitting unit and an organic light emitting unit adjacent to the secondary light emitting unit. The secondary light emitting unit is in a strip shape, or in a circular shape. In some embodiments, the secondary light emitting unit is in a quadrilateral shape.

In some embodiments, the light emitting device further includes a second type carrier transportation layer over the array of organic light emitting units. The first or second type carrier transportation layer is a composite structure.

In some embodiments not forming part of the claimed invention, a method of manufacturing a light emitting device includes providing a substrate; forming a first type carrier transportation layer over the substrate; forming a metallic layer on the first type carrier transportation layer; treating the surface of the metallic layer thereby driving a metallic element from the metallic layer into the first type carrier transportation layer; forming a photo sensitive organic light emitting layer over the first type carrier transportation layer; and patterning the photo sensitive organic light emitting layer to form a light emitting unit.

In some embodiments, the metallic layer includes a transition metal or treating the surface of the metallic layer includes one of heating, microwave, or plasma treatment. In some embodiments, the method further includes a first type carrier injection layer between the first type carrier transportation layer and the substrate.

A method of manufacturing a light emitting device is defined in claim <NUM> and includes providing a substrate and forming a plurality of photosensitive bumps over the substrate. The method also includes forming a photosensitive layer over the plurality of photosensitive bumps and patterning the photosensitive layer to form a recess through the photosensitive layer to expose a surface. The method also includes disposing an organic emissive layer on the surface, and removing the patterned photosensitive layer. The method further includes forming a buffer layer between the photosensitive layer and the plurality of photosensitive bumps. The buffer layer is organic and includes fluorine. The method further includes removing a portion of the buffer layer to partially expose the plurality of photosensitive bumps. The method may further include forming a first electrode between the substrate and the plurality of photosensitive bumps. The first electrode is partially covered by the plurality of photosensitive bumps. The method may further include forming a first type carrier injection layer between the first electrode and the photosensitive layer. The method may further include forming a carrier transportation layer over the organic emissive layer.

A light emitting device includes a substrate and a plurality of bumps over the substrate and a plurality of light emitting units between the plurality of bumps and over the substrate. Each light emitting unit includes a first electrode and an organic emissive layer over the first electrode. The device further includes a common first type carrier injection layer between the first electrode and the organic emissive layer, the common first type carrier injection layer being shared by the plurality of light emitting units. The light emitting device may further include a first type carrier transportation layer between the first type carrier injection layer and the organic emissive layer. The first type carrier transportation layer is commonly shared by the plurality of light emitting units. The light emitting device may further include a second type carrier transportation layer over the organic emissive layer, wherein the second type carrier is opposite to the first type carrier. The second type carrier transportation layer is commonly shared by the plurality of light emitting units. The light emitting device may further include a second electrode over the organic emissive layer. The second electrode is commonly shared by the plurality of light emitting units. In some embodiments, the plurality of bumps are made with black material which absorbs over <NUM>% of visible light. In some embodiments, the plurality of light emitting units are configured to emit at least two different colors.

The present disclosure provides a light emitting device, especially, organic light emitting device (OLED), and a method of manufacturing thereof. In the present disclosure, an organic light emitting layer in the OLED is formed by photo lithography. In some embodiments, the organic light emitting layer is a polymer light emitting layer. In some embodiments, the organic light emitting layer includes several light emitting pixels.

<FIG> illustrates an embodiment of an electronic device <NUM>. The electronic device <NUM> can be a rigid or a flexible display. Display <NUM> can have at least four different layers substantially stacked along a thickness direction X. Layer <NUM> is a substrate configured as a platform to have a light emitting layer <NUM> disposed thereon. Layer <NUM> is a cap layer to be disposed on the light emitting layer <NUM> and layer <NUM> is configured as a window for light emitting in/out the electronic device <NUM>. In some embodiments, layer <NUM> is an encapsulation layer. Layer <NUM> can also be configured as a touch interface for the user, therefore the surface hardness of the might be high enough to meet the design requirement. In some embodiments, layer <NUM> and layer <NUM> are integrated into one layer.

Layer <NUM> might be formed with a polymer matrix material. Layer <NUM> has a bend radius being not greater than about <NUM>. In some embodiments, layer <NUM> has a minimum bend radius being not greater than <NUM>. The minimum bend radius is measured to the inside curvature, is the minimum radius one can bend layer <NUM> without kinking it, damaging it, or shortening its life. In some embodiments, several conductive traces may be disposed in layer <NUM> and form circuitry to provide current to the light emitting layer <NUM>. In some embodiments, layer <NUM> includes graphene.

Light emitting layer <NUM>, can be configured as an array, as shown in <FIG>, including many light emitting units. A cross sectional view of along ling AA is illustrated in <FIG>. In some embodiments, the layer <NUM> has a substrate <NUM>. In some embodiments, the substrate is configured to be able to provide current to the light emitting units. In some embodiments, the light emitting units <NUM> are configured as mesa disposed on the substrate <NUM>. In some embodiments, the light emitting units are configured to be in recesses of the substrate <NUM>. A thickness "h" of the light emitting units may range from about -<NUM> to about <NUM>. The thickness h is measured from the surface 140a of the substrate <NUM>. The negative value means the light emitting unit is disposed in the recess. Positive means light emitting unit protrudes like mesa shown in <FIG>. The light emitting units can be arranged in an array. Each independent light emitting unit is separated from other adjacent light emitting units. A gap, d, represents a separation distance between two adjacent light emitting units. In some embodiments, gap, d, is between about <NUM> and about <NUM>. In some embodiments, the gap, d, is controlled to be at least not greater than about <NUM> so that the density of the units can be designed to be at least more than <NUM> ppi or <NUM> ppi.

In some embodiments, a light emitting unit has a width, w, being between about <NUM> and about <NUM>. The light emitting unit is a polymeric material. In some embodiments, the light emitting unit is photo sensitive. In some embodiments the width, w, is not greater than about <NUM>.

<FIG> illustrates an embodiment of a light emitting pixel <NUM> in a light emitting layer from a crossectional view perspective. The light emitting pixel <NUM> includes a light emitting unit <NUM> as the light emitting unit in <FIG>. Further, the light emitting pixel <NUM> includes a first type carrier transportation layer <NUM> and a second type carrier transportation layer <NUM>. The first type is opposite to the second type. In some embodiments, the first type transportation layer <NUM> is a hole transportation layer (HTL) and the second type carrier transportation layer <NUM> is an electron transportation layer (ETL). In some embodiments, the first type transportation layer <NUM> is an electron transportation layer (ETL) and the second type carrier transportation layer <NUM> is a hole transportation layer (HTL).

In some embodiments, trace of metal is found in the first type carrier transportation layer <NUM> or the second type carrier transportation layer <NUM>. Moreover, metal element may appear first type carrier transportation layer <NUM> or the second type carrier transportation layer <NUM>. The metal element includes transition metal. In some embodiments, the metal element includes at one of the elements, Y, Zr, Nb, Mo, Ru, Rh, Cd, Hf, Ta, W, Re, Os.

In some embodiments, the light emitting unit <NUM> is in contact with the first type transportation layer <NUM>. In some embodiments, the light emitting unit <NUM> is in contact with the second type transportation layer <NUM>. In some embodiments, an intermediate layer is between the light emitting unit <NUM> and the first type transportation layer <NUM>. In some embodiments, an intermediate layer is between the light emitting unit <NUM> and the second type transportation layer <NUM>.

<FIG> is an enlarged view of the light emitting unit <NUM> in <FIG> in according to some embodiments. The light emitting unit <NUM> has a footing 243a extended laterally from the sidewall <NUM> of the light emitting unit <NUM>. The footing 243a is in contact with the first type transportation layer <NUM>. The lateral extension of the footing 243a has a width, e, which is measured from the sidewall <NUM> to the tip of the footing 243a. The tip is farthest point where the footing 243a can extend. The tip is also the end point where the footing meets the first type transportation layer <NUM>.

<FIG> illustrates another embodiment of a light emitting unit <NUM> in <FIG>. The sidewall <NUM> of the light emitting unit is tapered and has two different slopes. The first slope is measured from the tip F1 of the footing 243a to the turning point F2. The second slope is measured from the turning point F2 to the top corner F3 of the light emitting unit <NUM>. In some embodiments, the second slope is greater than the first slope.

One of the purposes to have a footing 243a extended from the bottom of the light emitting unit <NUM> is to increase the adhesion between the light emitting unit <NUM> and the first type transportation layer <NUM>. Because the light emitting unit <NUM> and the first type transportation layer <NUM> may be formed with different materials, the surface tension between the light emitting unit <NUM> and the first type transportation layer <NUM> may cause undesired peeling. With the footing 243a, the contact surface between the light emitting unit <NUM> and the first type transportation layer <NUM> is increased to secure the light emitting unit <NUM> sitting on the first type transportation layer <NUM>.

In some embodiments, there are some secondary light emitting unit 243b disposed between two adjacent light emitting unit <NUM>. The secondary light emitting unit 243b has a height that is smaller than the height, h, of the light emitting unit <NUM>. The secondary light emitting unit 243b is isolated from the light emitting unit <NUM>. In some embodiments, the height of the secondary light emitting unit 243b is about <NUM>/<NUM> to about <NUM>/<NUM> of the height of the light emitting unit <NUM>.

In some embodiments, the light emitting unit <NUM> and an adjacent secondary light emitting unit 243b emit a light with a same wavelength. In some embodiments, some light emitting units are designed to emit a light with a first wavelength. Some light emitting units are designed to emit a light with a second wavelength, which is different from the first wavelength. Some light emitting units are designed to emit a light with a third wavelength, which is different from the first wavelength and the second wavelength. One light emitting unit may be assigned to have a secondary light emitting unit disposed adjacent to the light emitting unit and the assigned secondary light emitting unit emits a light with the same wavelength as the corresponding light emitting unit.

Aspect ratio of light emitting unit <NUM> is defined as the height h of the light emitting unit <NUM> divided by the gap, d, between two adjacent light emitting units. As shown in <FIG>, when the height ratio between the secondary light emitting unit 243b and the light emitting unit <NUM> reaches <NUM>/<NUM>, the aspect ratio start entering into a saturation zone until the height ratio reaches <NUM>/<NUM>. For an ultra-high PPI (><NUM> ppi) display, the designer can adjust the height ratio between the secondary light emitting unit 243b and the light emitting unit <NUM> in order to meet the requirement of the aspect ratio.

<FIG> is a top view of an embodiment of an array of light emitting unit <NUM> disposed on a first type transportation layer <NUM>. The secondary light emitting unit 243b can be formed as in quadrilateral, circle, or a strip shape.

In some embodiments, a secondary light emitting unit 243b is formed to be in corresponding to only one pair of light emitting units <NUM>. The secondary light emitting unit 243b is designed to improve the aspect ratio of the gap between of the pair of light emitting units <NUM>. In some embodiments, a circular shaped secondary light emitting unit 243b may increase the maximum aspect ratio (Max in <FIG>) to be <NUM>% to <NUM>% higher than a quadrilateral one.

In some embodiments, a secondary light emitting unit 243b is formed to be in corresponding to several pairs of light emitting units <NUM>. Like the one in a strip pattern at left side, the strip-like secondary light emitting unit 243b is designed to be corresponding to at least three different pairs of light emitting units <NUM>.

In some embodiments, there are at least two separate secondary light emitting units 243b formed to be in corresponding to several pairs of light emitting units <NUM>. As the two strip-like light emitting units 243b at the right side, there are two secondary light emitting strips in parallel.

In order to minimize the interference between adjacent light emitting units <NUM>, an absorption material <NUM> can be used to fill the gaps between light emitting units <NUM> as shown in <FIG>. The absorption material <NUM> can absorb the light emitted from the light emitting units <NUM> and any visible light entering into the device from ambient.

In some embodiments, the first type carrier transportation layer <NUM> is a composite structure and includes at least a primary layer 241a and a secondary transportation layer 241b as in <FIG>. The trace of metal is found in any one sub-layer of the first type carrier transportation layer <NUM>. The metal element includes transition metal. In some embodiments, the metal element includes at one of the elements, Y, Zr, Nb, Mo, Ru, Rh, Cd, Hf, Ta, W, Re, Os.

Similarly, in some embodiments, the second type carrier transportation layer <NUM> is a composite structure and includes at least a primary layer and a secondary transportation layer. The trace of metal is found in any one sub-layer of the second type carrier transportation layer <NUM>. The metal element includes transition metal. In some embodiments, the metal element includes at one of the elements, Y, Zr, Nb, Mo, Ru, Rh, Cd, Hf, Ta, W, Re, Os. In some embodiments, layer <NUM> or <NUM> may include Cs, Rb, K, Na, Li, Yb, Lu, Tm, etc..

In some embodiments, there is a first type carrier injection layer adjacent to the first type carrier transportation layer. As in <FIG>, the first type carrier injection layer <NUM> is adjacent to the first type carrier transportation layer <NUM>. Similarly, there is a second type carrier injection layer adjacent to the second type carrier transportation layer.

<FIG> illustrate some operations of manufacturing a light emitting device. In <FIG>, a substrate including a first type carrier injection layer <NUM> and a composite first type carrier transportation layer is provided.

In <FIG>, a metal or metal complex layer <NUM> is disposed on the composite first type carrier transportation layer. The metal complex layer can be formed by various deposition processes such as, vapor deposition, sputtering, atomic layer deposition (ALD), heat evaporation, coating, or jetting. In some embodiments, the thickness of layer <NUM> is about 30Å or less. Layer <NUM> may include oxygen, nitrogen, argon, fluorine, carbon, etc..

A treatment process is introduced in <FIG>. The treatment process can be performed by heating, microwave, plasma treatment. The treatment is applied directly on layer <NUM>. During the treatment, layer <NUM> is broken down such that transitional metal element <NUM> in layer <NUM> can penetrate into the first type carrier transportation layer <NUM>. In some embodiments, the distribution of the transitional metal element <NUM> may have a gradient. In some embodiments, a density of the transitional metal element <NUM> at the top surface of the first type carrier transportation layer <NUM> is higher than a density at a location proximal to the interface between first type carrier transportation layer <NUM> and the first type carrier injection layer <NUM>. Similarly, the above metal diffusion operation can be applied to the second type carrier transportation layer.

After the treatment, the layer <NUM> may disappear or be removed from the surface of the first type carrier transportation layer <NUM>. A photo sensitive organic light emitting layer <NUM> is disposed over the first type carrier transportation layer <NUM> after the treatment or removal process as in <FIG>.

In <FIG>, a patterning process, such as photolithography, is introduced to remove excessive portion and form a light emitting unit <NUM>.

<FIG> illustrate another embodiment to form light emitting units <NUM> on a substrate <NUM>. In some embodiments, the substrate <NUM> includes a carrier transportation layer. In some embodiments, the substrate <NUM> includes a TFT (thin film transistor) array. In <FIG>, a patterned photosensitive layer <NUM> is formed on the substrate <NUM>. In some embodiments, the patterned photosensitive layer <NUM> is a photo absorption material as the photo absorption material <NUM> in <FIG>. In some embodiments, the patterned photosensitive layer <NUM> is used as a pattern defined layer. A region 251a is defined by two adjacent patterned photosensitive mesas and the region 251a is configured to receive an organic light emitting unit. In some embodiments, the patterned photosensitive layer <NUM> is fluorine free, i.e. substantially contains no fluorine.

In <FIG>, a photo resist layer <NUM> is disposed over the photosensitive layer <NUM> and in the region 251a. In some embodiments, the photo resist layer <NUM> contains fluorine. In <FIG>, the photo resist layer <NUM> is patterned to have openings 253a. In some embodiments, each opening 253a has a width less than about <NUM>. In <FIG>, an organic light emitting unit <NUM> is formed in the opening 253a. In some embodiments, the organic light emitting unit <NUM> has a height that is smaller than a height of the photosensitive layer <NUM>. The photo resist layer <NUM> can be removed in another step (not shown in the drawings).

In <FIG>, a substrate <NUM> is provided, the substrate <NUM> may include a TFT (thin film transistor) array. Several first electrode <NUM> are disposed over the substrate <NUM>. Each first electrode <NUM> is configured to be connected to a circuit embedded in the substrate <NUM> at one side and to be in contact with a light emitting material at the other side. The pattern of the first electrode array is designed for the pixel arrangement. A photosensitive layer <NUM> is disposed over the first electrodes <NUM> and the substrate <NUM>. In some embodiments, the photosensitive layer <NUM> is spin-coated over the first electrodes <NUM> and the substrate <NUM>.

The photosensitive layer <NUM> fills into the gap between adjacent first electrodes. The photosensitive layer <NUM> is heated to a predetermined temperature then exposed under a designated wavelength. The photosensitive layer <NUM> may absorb over <NUM>% of the visible light and is also called black material in the present disclosure. After exposure, the photosensitive layer <NUM> is rinsed in a solution for development. A portion of the photosensitive layer <NUM> is removed and the remaining portion is substantially covering the gap between adjacent first electrodes as shown in <FIG>. In the cross sectional view, the remaining photosensitive layer <NUM> form several bumps <NUM>, each bump <NUM> fills the gap of two adjacent first electrodes. Each first electrode <NUM> is partially covered by the bump <NUM>. The patterned bumps <NUM> are also called pixel defined layer (PDL).

The bump <NUM> can be formed in different types of shape. In <FIG>, the bump <NUM> has a curved surface. In some embodiments, the shape of bump <NUM> is tapezoid. After the bumps <NUM> formed, a cleaning operation is performed to clean the exposed surfaces of the bumps <NUM> and the first electrodes <NUM>. In one embodiment, during the cleaing operation, a DI (De-Ionized) water is heated to a tempature between <NUM> and <NUM>. After the temperture of DI water is elevated to a predetermined temperature then is introduced to the exposed surfaces of the bumps <NUM> and the first electrodes <NUM>.

In some embodiments, ultrsonic is used during the cleaning operation. The ultrasoic is introduced into the cleaning agent, such as water or IPA, etc. In some embodiments, carbon dioxide is introduced into the cleaning agent. After the cleaning operation, the cleaning agent is removed from the exposed surfaces via a heating operation. During the heating operation, the substrate <NUM> and the bump <NUM> may be heated to a temperature between about <NUM> and <NUM>. In some cases, an compressed air is introduced to the exposed surfaces to help remove the residue of clean agent while heating.

After the heating operation, the exposed surfaces may be treated with an O<NUM>, N<NUM>, or Ar plasma. The plasma is used to roughened the exposed surfaces. In some embodiments, an ozone gas is used to adjust the surface condition of the exposed surfaces.

A carrier injection layer <NUM> is disposed over the exposed surfaces of the bumps <NUM> and the first electrodes <NUM> as in <FIG>. The carrier injection layer <NUM> is continuously lining along the exposed surfaces. More specifically, the exposed surface of each first electrode <NUM> is configured as an effective light emitting area for one light emitting unit. In this embodiment, all light emitting units use a common carrier injection layer <NUM>. In some embodiments, layer <NUM> is for hole injection. In some embodiments, layer <NUM> is for electron injection. The carrier injection layer <NUM> continuously overlies several PDL bumps <NUM> and first electrodes <NUM>. Optionally, the carrier injection layer <NUM> is in contact with the PDL bumps <NUM>. In one embodiment, the carrier injection layer <NUM> is in contact with the first electrodes <NUM>. In some embodiments, the carrier injection layer <NUM> is organic.

A carrier transportation layer <NUM> (or called first type carrier transportation layer) is disposed over the exposed surfaces of the bumps <NUM> and the first electrodes <NUM> as in <FIG>. The carrier injection layer <NUM> is disposed under the carrier transportation layer <NUM>. The carrier transportation layer <NUM> is continuously lining along the carrier transportation layer <NUM>. In this embodiment, all light emitting units use a common carrier transportation layer <NUM>. In some embodiments, layer <NUM> is for hole transportation. In some embodiments, layer <NUM> is for electron transportation. The carrier transportation layer <NUM> continuously overlies several PDL bumps <NUM> and first electrodes <NUM>. Optionally, the carrier transportation layer <NUM> is in contact with the carrier injection layer <NUM>. In some embodiments, the carrier transportation layer <NUM> is organic.

In some embodiments, the carrier transportation layer <NUM> is configured to be broken into segements and the carrier injection layer <NUM> is continuously lining along the exposed PDL bumps and first electrodes as shown in <FIG>. Each segment is vertically aligned to a first electrode <NUM>. In other words, the carrier transportation layer <NUM> is not continuously lining along the carrier injection layer <NUM>. Each light emitting unit has a separate carrier transportation layer disposed thereon.

In some embodiments, the carrier injection layer <NUM> is configured to be broken into segements and the carrier transportation layer <NUM> is continuously lining along the exposed PDL bumps and the segmented carrier injection layer <NUM> as shown in <FIG>. Each segment is vertically aligned to a first electrode <NUM>. In other words, the carrier injection layer <NUM> is not continuously lining along the exposed bumps <NUM> and first electrode <NUM>. Each light emitting unit has a separate carrier injection layer <NUM> disposed thereon.

A buffer layer <NUM> is disposed over the PDL bumps <NUM> and also covers the carrier injection layer <NUM> and carrier transportation layer <NUM>, as shown in <FIG>. The buffer layer <NUM> is used to block moisture penetrating into the PDL bumps <NUM>, and the carrier injection layer <NUM> and carrier transportation layer <NUM>. In one embodiment, the buffer <NUM> is disposed by spin coating. The buffer layer <NUM> can be further heated to a temperature T<NUM>. In some embodiments, T<NUM> is about <NUM> to <NUM> below the glass temperature of the carrier injection layer <NUM> and carrier transportation layer <NUM>. The heating operation is about <NUM> to <NUM> minutes. In some embodiments, the buffer layer <NUM> includes fluorine.

In <FIG>, a photosensitive layer <NUM> is disposed over the buffer layer <NUM> after the heating operation. The photosensitive layer <NUM> is further patterned by a lithography process to expose a portion of buffer layer <NUM> through the recess <NUM>. In <FIG>, a portion of the buffer layer <NUM> is removed to have a recess <NUM> to expose the carrier transportation layer <NUM>. In some embodiments, the removal operation in <FIG> is performed by wet etch.

According to the invention, the removal operation includes at least two steps. The first step is vertical removal and the buffer layer <NUM> is carved out substantially following the dimension of opening width of the recess <NUM> as shown in <FIG>. After forming the recess <NUM>, a second step is introduced to perform a lateral removal as shown in <FIG>. An undercut <NUM> is formed to expand the recess <NUM> further into the buffer layer <NUM> in order to expose more surfaces toward the topmost point of the PDL bump <NUM>.

An organic emissive (EM) layer <NUM> is disposed into the recess <NUM> and covering the carrier transportation layer <NUM> and the photosensitive layer <NUM>. In <FIG>, the EM layer <NUM> fully covers the exposed carrier transportation layer <NUM>. The EM layer <NUM> is configured to emit a first color.

An organic carrier transportation layer <NUM> (or called second type carrier transportation layer) is disposed over the EM layer <NUM> as shown in <FIG>. The organic carrier transportation layer <NUM> can be a hole or electron transportation layer <NUM>. In some embodiments, the organic carrier transportation layer <NUM> and the carrier transportation layer <NUM> is repectively configured for opposite types of charges.

In <FIG>, a second electrode <NUM> can be disposed over the organic carrier transportation layer <NUM>. A top surface of the photosensitive layer <NUM> is also covered by the second electrode <NUM>. The photosensitive layer <NUM> can be removed after forming the second electrode <NUM>. The second electrode <NUM> can be metallic material such as Ag, Mg, etc. In some embodiments, the second electrode <NUM> includes ITO (indium tin oxide), or IZO (indium zinc oxide). In some embodiments, each light emitting unit has an independent second electrode <NUM> from a cross sectional point of view and several light emitting units share a common carrier transportation layer <NUM>.

Similar operations like <FIG> can be repeated to form a different colored light emitting unit. <FIG> illustrates another light emitting unit emitting a second color, which is different from the first color. The second electrode <NUM> for the first light emitting unit <NUM> and the second light emitting unit <NUM> is continuous. Each light emitting unit has an independent carrier transportation layer <NUM>. The independent carrier transportation layer <NUM> is segmented to have several pieces and each piece is disposed in one light emitting unit. In some embodiments, several light emitting units share a common carrier transportation layer <NUM>.

In some embodiments, each light emitting unit has an independent carrier transportation layer <NUM> (proximal to the first electrode <NUM> comparing to the carrier transportation layer <NUM>) as in <FIG>. The carrier transportation layer <NUM> is segmented to have several pieces and each piece is disposed in one light emitting unit. In some embodiments, several light emitting units share a common carrier transportation layer <NUM>. Each light emitting unit has an independent carrier injection layer <NUM>. The carrier injection layer <NUM> is segmented to have several pieces and each piece is disposed in one light emitting unit. In some embodiments, several light emitting units share a common carrier injection layer <NUM>.

In some embodiments, the second carrier transportation layer <NUM> has at least two sublayers. The first sub-layer is between the second sublayer and the EM layer <NUM>. In some embodiments, the second sublayer is between the first sublayer and the electrode. In some embodiments, both sublayers are continuous and light emitting units <NUM> and <NUM> use common first sub-layer and second sublayer. In some embodiments, one sub-layer is segmented and ther other one is continuous. In some embodiments, the first sublayer is continuous and the second sub-layer is segmentd. Each light emitting unit has an independent second sublayer. In some embodiments, the second sub-layer is continuous and the first sub-layer is segmentd. Each light emitting unit has an independent first sub-layer.

Claim 1:
A method of manufacturing a light emitting device, comprising:
providing a substrate (<NUM>, <NUM>);
forming a plurality of photosensitive bumps (<NUM>) over the substrate (<NUM>, <NUM>); and
forming a photosensitive layer (<NUM>) over the plurality of photosensitive bumps (<NUM>);
said method characterized by further comprising:
forming a buffer layer (<NUM>) between the photosensitive layer (<NUM>) and the photosensitive bumps (<NUM>);
vertically patterning the photosensitive layer (<NUM>) and the buffer layer (<NUM>) to form a recess (<NUM>, <NUM>) through the photosensitive layer (<NUM>) and the buffer layer (<NUM>);
laterally and partially removing the buffer layer (<NUM>) to expand the recess (<NUM>) and form a undercut (<NUM>) to expose a surface;
disposing an organic emissive layer (<NUM>) on the surface, and
removing the patterned photosensitive layer (<NUM>) and the buffer layer (<NUM>).