Patent Publication Number: US-11398600-B2

Title: Method for manufacturing electroluminescent device

Description:
TECHNICAL FIELD 
     The present disclosure is related to a method for manufacturing an electroluminescent device, and more particularly, to a method for manufacturing an organic light-emitting device. 
     BACKGROUND 
     Organic light-emitting diodes (OLEDs) have been widely used in displays due to their advantages in latency, contrast ratio, response time, and black levels. However, due to the constraints of current color-patterning technologies, the commercialization of high-resolution OLED displays remains limited. Related manufacturing issues include low manufacturing yield, high fabrication cost, and low display quality. Therefore, the OLED industry is seeking routes to address the above issues. 
     SUMMARY 
     A method of manufacturing an electroluminescent device includes forming a first patterned structure in a first pixel through a first opening of a first sacrificial layer removing the first sacrificial layer; forming a second patterned structure in a second pixel through a second opening of a second sacrificial layer; removing the second sacrificial layer; and removing a first patterned protecting layer from the first patterned structure and a second patterned protecting layer from the second patterned structure to respectively form a first patterned light-emitting layer in the first pixel and a second patterned light-emitting layer in the second pixel. 
     In some embodiments, the forming of the first patterned structure and the removing of the first sacrificial layer further include forming a first light-emitting layer and a first protecting layer over the first sacrificial layer and over the first pixel through the first opening; and removing the first sacrificial layer together with an overlying portion of the first light-emitting layer and an overlying portion of the first protecting layer to form the first patterned structure including the first patterned light-emitting layer and the first patterned protecting layer. 
     In some embodiments, the forming of the second patterned structure and the removing of the second sacrificial layer further include forming a second light-emitting layer and a second protecting layer over the second sacrificial layer and over the second pixel through the second opening; and removing the second sacrificial layer together with an overlying portion of the second light-emitting layer and an overlying portion of the second protecting layer to form the second patterned structure including the second patterned light-emitting layer and the second patterned protecting layer. 
     In some embodiments, the removing of the first sacrificial layer is performed prior to the removing of the second sacrificial layer. 
     In some embodiments, the removing of the first patterned protecting layer is performed together with the removing of the second patterned protecting layer 
     In some embodiments, the first patterned protecting layer and the second patterned protecting layer are disposed over the first patterned light-emitting layer and the second patterned light-emitting layer, respectively. 
     In some embodiments, a thickness of the first patterned protecting layer is substantially the same as a thickness of the second patterned protecting layer. 
     In some embodiments, the first patterned protecting layer and the second patterned protecting layer include halogen-containing protecting layers. 
     In some embodiments, the first patterned protecting layer and the second patterned protecting layer include halogen-free protecting layers. 
     In some embodiments, the first patterned protecting layer is soluble in an etchant and the first patterned light-emitting layer is insoluble or less soluble in the etchant. 
     In some embodiments, the etchant includes halogen-containing solvents. 
     In some embodiments, the etchant includes halogen-free solvents. 
     In some embodiments, the method further includes forming a pixel-defining layer to separate the first pixel from the second pixel prior to forming the first patterned structure and the second patterned structure. 
     A method of manufacturing a light-emitting device includes providing a substrate including a first pixel and a second pixel configured to emit different colors; forming a first light-emitting layer and a first protecting layer over the substrate through a first opening of a first sacrificial layer; forming a second light-emitting layer and a second protecting layer over the substrate through a second opening of a second sacrificial layer; and simultaneously removing the first protecting layer from the first light-emitting layer and the second protecting layer from the second light-emitting layer. 
     In some embodiments, the method further includes removing the first sacrificial layer prior to forming the second light-emitting layer and the second protecting layer. 
     In some embodiments, an etch selectivity of the first protecting layer and the second protecting layer are greater than that of the first light-emitting layer and the second light-emitting layer. 
     In some embodiments, the first protecting layer and the second protecting layer include fluorine materials. 
     In some embodiments, the first protecting layer and the second protecting layer are substantially free of fluorine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an intermediate stage in the manufacture of an electroluminescent device in accordance with some embodiments of the present disclosure. 
         FIG. 2  illustrates a top view of the intermediate stage in the manufacture of the electroluminescent device according to some embodiments of the present disclosure. 
         FIGS. 3A to 3L  illustrate a method of manufacturing an electroluminescent device according to some embodiments of the present disclosure. 
         FIGS. 4A to 4F  illustrate a method of manufacturing an electroluminescent device according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” “on,” “over,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     To achieve successful commercialization of high-resolution OLED displays, a method with low cost and high productivity is desired. One color-patterning method for OLED displays is the photolithography method. RGB color patterning is performed by lift-off processes of red, green and blue materials through a patterned photomask. This technique is widely used due to the high resolution of the displays produced. However, this method has several inherent limitations, including OLED degradation due to UV light exposure, and high fabrication cost due to the expensive production procedures of the photomask. These limitations present obstacles to the successful commercialization of high-resolution OLED displays and result in reduced display quality. 
     In the present disclosure, a protecting layer is formed on an organic light-emitting layer in the OLED. The protecting layer covering the organic light-emitting layer protects the organic light-emitting layer, and thus the organic light-emitting layer incurs less damage during the photolithography process. In addition, the protecting layer is disposed only temporarily to protect the organic light-emitting layer during fabrication, and is subsequently removed. 
       FIG. 1  illustrates an intermediate stage in the manufacture of an electroluminescent device in accordance with some embodiments of the present disclosure. As shown in  FIG. 1 , a substrate  10  is provided. The electroluminescent device may be a light-emitting device. By way of example, the electroluminescent device may be an organic light-emitting diode (OLED). In some embodiments, the electroluminescent device may be a top emission OLED, a bottom emission OLED or a transparent OLED that can be made to be both top- and bottom-emitting. 
     The substrate  10  may be a rigid or a flexible substrate. In addition, the substrate  10  may be an opaque or a transparent substrate. The substrate  10  can include glass, quartz, semiconductive material such as silicon, I-V group compound, or other suitable material. In some embodiments, the substrate  10  includes graphene. In some embodiments, the substrate  10  may be formed with a polymer matrix material. A dielectric layer  11  is optionally disposed over the substrate  10  as shown in  FIG. 1 . In some embodiments, the dielectric layer  11  may be made with silicon oxide, silicon nitride, silicon oxynitride, or other suitable materials. 
     As shown in  FIG. 1 , a plurality of light-emitting devices are disposed on the substrate  10 . The light-emitting devices include a first light-emitting device  16 G configured to emit a first light beam and a second light-emitting device  16 R configured to emit a second light beam having a wavelength different from that of the first light beam. In addition, the first light beam is substantially within a first wavelength range, and the second light beam is substantially within a second wavelength range. In some embodiments, the light-emitting devices further include a third light-emitting device  16 B configured to emit a third light beam having a wavelength different from those of the first light beam and the second light beam. The third light beam is substantially within a third wavelength range. In some embodiments, the first wavelength range includes wavelengths less than wavelengths included in the second wavelength range, and the third wavelength range includes wavelengths less than wavelengths included in the first wavelength range. Particularly, the first wavelength range is from about 495 to about 570 nm, the second wavelength range is from about 620 to about 750 nm and the third wavelength range is from about 430 to about 470 nm. More specifically, the first light beam is green light, the second light beam is red light, and the third light beam is blue light. 
     The plurality of light-emitting devices may have several sublayers stacked over the substrate  10 . In some embodiments, the plurality of light-emitting devices may have a first electrode  13 , a first carrier-injection layer  22 , a first carrier-transportation layer  24 , a light-emitting layer, a second carrier-transportation layer  26 , a second carrier-injection layer  28  and a second electrode  14 . 
     The first electrodes  13  are disposed over the dielectric layer  11  as shown in  FIG. 1 . The first electrodes  13  may include conductive materials. Specifically, the first electrodes  13  can be metal such as aluminum (Al), copper (Cu), silver (Ag), gold (Au), tungsten (W), etc. or metal alloy. In some embodiments, the first electrodes  13  can be transparent conductive material such as metal oxide. The first electrodes  13  are electrically and respectively connected to the light-emitting devices. In some embodiments, the first electrodes  13  are designed as anodes of the light-emitting devices. 
     A pixel-defining layer (also referred to as a PDL)  20  including a plurality of spacers is formed on the substrate  10  and separates the first electrodes  13  from one another when viewed in a thickness direction of the electroluminescent device. The pixel-defining layer  20  may be optionally disposed over the dielectric layer  11  as shown in  FIG. 1 . In some embodiments, the pixel-defining layer  20  partially covers the first electrodes  13  and leaves a portion of the first electrodes  13  open to receive the light-emitting devices. In some embodiments, the pixel-defining layer  20  includes polymeric material, photosensitive material or photo absorption material. In some embodiments, the pixel-defining layer  20  is formed through a photolithography operation. 
     The first carrier-injection layer  22  is disposed over the exposed surfaces of the pixel-defining layer  20  and the first electrodes  13 . The first carrier-injection layer  22  is continuously formed across the pixel-defining layer  20  and the first electrodes  13 . More specifically, the exposed surface of each first electrode  13  is configured as an effective light-emitting area for a light-emitting device. In this embodiment, all light-emitting devices use a common first carrier-injection layer  22 . In some embodiments, the first carrier-injection layer  22  performs hole injection. In some embodiments, the first carrier-injection layer  22  performs electron injection. The first carrier-injection layer  22  continuously overlies the pixel-defining layer  20  and the first electrodes  13  as illustrated in  FIG. 1 . In some embodiments, the first carrier-injection layer  22  is organic. 
     The first carrier-transportation layer  24  is disposed over the pixel-defining layer  20  and the first electrodes  13 . The first carrier-injection layer  22  is disposed under the first carrier-transportation layer  24 . The first carrier-transportation layer  24  is continuously formed across the first carrier-injection layer  22 . In this embodiment, all light-emitting devices use a common first carrier-transportation layer  24 . In some embodiments, the first carrier-transportation layer  24  performs hole transportation. In some embodiments, the first carrier-transportation layer  24  performs electron transportation. The first carrier-transportation layer  24  continuously overlies the pixel-defining layer  20  and the first electrodes  24 . In some embodiments, the first carrier-transportation layer  24  is organic. 
     A plurality of light-emitting layers is formed above the surfaces of the first electrodes  13 . In some embodiments, the light-emitting layers may include a first light-emitting layer  30 G, a second light-emitting layer  30 R, and a third light-emitting layer  30 B. The first light-emitting layer  30 G, the second light-emitting layer  30 R, and the third light-emitting layer  30 B are respectively disposed on the first carrier-transportation layer  24 . In some embodiments, a portion of the light-emitting layers may be formed on or over the pixel-defining layer  20  as illustrated in  FIG. 1 . 
     A plurality of the second carrier-transportation layers  26  is disposed on the first light-emitting layer  30 G, the second light-emitting layer  30 R, and the third light-emitting layer  30 B respectively. In some embodiments, all light-emitting devices may use a common second carrier-transportation layer  26 . The second carrier-transportation layer  26  may be used for electron transportation. In some embodiments, the second carrier-transportation layer  26  performs hole transportation. The second carrier-transportation layer  26  partially overlies the pixel-defining layer  20 . The second carrier-transportation layer  26  may include organic material. 
     A plurality of the second carrier-injection layers  28  is disposed on the second carrier-transportation layer  26 . The second carrier-injection layer  28  is formed across the exposed surfaces of the second carrier-transportation layer  26 . In some embodiments, all light-emitting devices use a common second carrier-injection layer  28 . The second carrier-injection layer  28  may be used for electron injection. In some embodiments, the second carrier-injection layer  28  performs hole injection. The second carrier-injection layer  28  may include organic material. 
     The second electrode  14  is formed above the light-emitting layers. The second electrode may include conductive materials. In some embodiments, the second electrode  14  may be provided as a transparent electrode. Examples of the transparent conductive material may include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO) and indium-doped cadmium oxide. In some embodiments, the second electrode  108  may be designed as cathode of the light-emitting device. 
     An encapsulation layer  15  for protecting the light-emitting layers from external environment factors such as moisture or oxygen may be provided on the second electrode  14 . The encapsulation layer  15  may be formed of a thin film encapsulation layer in which a plurality of organic layers and inorganic layers crossing each other are laminated. In some embodiments, the encapsulation layer  15  may include a plurality of organic layers and a plurality of inorganic layers, which are alternately laminated. The organic layers may be formed of acrylate-based materials and the inorganic layers may be formed of oxide-based materials, but the disclosure is not limited thereto. 
       FIG. 2  illustrates a top view of the intermediate stage in the manufacture of the electroluminescent device according to some embodiments of the present disclosure. As shown in  FIG. 2 , the substrate  10  includes a plurality of pixels  12 . The pixels  12  can be arranged in an array. Each independent pixel  12  is separated from other adjacent pixels  12 . Each pixel  12  includes a first sub-pixel  12 G, a second sub-pixel  12 R and a third sub-pixel  12 B. In some embodiments, the sub-pixel may be also referred to as the sub-pixel region or the pixel. 
     The first sub-pixel  12 G, the second sub-pixel  12 R and the third sub-pixel  12 B may be configured to display different colors. Specifically, the first sub-pixel  12 G, the second sub-pixel  12 R and the third sub-pixel  12 B may be configured to emit an image of a first color, an image of a second color and an image of a third color, respectively. For example, the first sub-pixel  12 G may be configured to display the color green, the second sub-pixel  12 R may be configured to display the color red and the third sub-pixel  12 B may be configured to display the color blue. 
     As shown in  FIG. 2 , the arrangement of the sub-pixels includes, from left to right, the first sub-pixel  12 G, the second sub-pixel  12 R and then the third sub-pixel  12 B, but is not limited thereto. The configuration of the sub-pixels may be altered according to the design or other considerations. For example, the arrangement of the sub-pixels may include, from left to right, the first sub-pixel  12 G, the third sub-pixel  12 B, then the second sub-pixel  12 R. Further, although the sub-pixels illustrated in  FIG. 2  are square in shape, the sub-pixels may have other suitable shapes. In addition, the number of sub-pixels in one pixel  12  may be, but is not limited to, three. Alternatively, the number of sub-pixels may be altered and there may be other suitable sub-pixels configured to display different colors, such as yellow, white or other colors. 
       FIGS. 3A to 3K  illustrate a method of manufacturing an electroluminescent device according to some embodiments of the present disclosure. As shown in  FIG. 3A , a pixel-defining layer  20  is optionally formed over the substrate  10  to separate the first sub-pixel  12 G and the second sub-pixel  12 R. The pixel-defining layer  20  can be arranged so as to form a grid when viewed in the thickness direction of the electroluminescent device. The pattern of the pixel-defining layer  20  is designed in accordance with the desired pixel arrangement. In the present embodiment, the number of sub-pixels in one pixel  12  is two sub-pixels, but is not limited thereto. 
     As shown in  FIG. 3B , a first sacrificial layer  30  is formed over the substrate  10 . The first sacrificial layer  30  covers the first sub-pixel  12 G and the second sub-pixel  12 R. In some embodiments, the first sacrificial layer  30  includes a photosensitive layer. The first sacrificial layer  30  may additionally include a releasing layer (not shown) on the substrate  10 . The releasing layer may be disposed between the photosensitive layer and the substrate  10 . The releasing layer may serve as a planarization layer to increase the flatness of the first sacrificial layer  30  or as an adhesion layer to increase the adhesion between the photosensitive layer and the pixel-defining layer  20 . 
     As shown in  FIG. 3C , the first sacrificial layer  30  is patterned to form a first opening  32  exposing the first sub-pixel  12 G. Specifically, the first sacrificial layer  30  is patterned by a photolithography process. The first sacrificial layer  30  may be heated to a predetermined temperature, then exposed to radiation of a designated wavelength. After exposure, the first sacrificial layer  30  is rinsed in a solution for development. A portion of the first sacrificial layer  30  is removed and the remaining portion is left substantially covering the second sub-pixel  12 R. 
     As shown in  FIG. 3D , a first light-emitting layer  40 G is formed over the substrate  10 . The first light-emitting layer  40 G is formed over the first sacrificial layer  30  and on the first sub-pixel  12 G through the first opening  32  of the first sacrificial layer  30 . The first light-emitting layer  40 G may be configured to display an image of a first color. In some embodiments, the first light-emitting layer  40 G may be configured to display the color green. 
     In some embodiments, the first light-emitting layer  40 G is organic. The first light-emitting layer  40 G may be formed by a physical vapor deposition (PVD) process. A heat source evaporates organic light-emitting materials, but vapor deposition can be controlled precisely with the use of a shadow mask. The organic molecules travel through the holes of the shadow mask before reaching the substrate  10 . The PVD process can include sputtering (magnetron or ion beam), which utilizes energetic ions colliding with a target to eject (or sputter) target material, or evaporation (thermal resistive or e-beam), which relies on heating a solid source material above its vaporization temperature. 
     As shown in  FIG. 3E , a first protecting layer  50 G is formed over the substrate  10 . The first protecting layer  50 G is formed over the first sacrificial layer  30  and on the first sub-pixel  12 G through the first opening  32  of the first sacrificial layer  30 . In some embodiments, the first protecting layer  50 G is formed over the first light-emitting layer  40 G. The first protecting layer  50 G may be configured to protect the underlying first light-emitting layer  40 G. In some embodiments, the first protecting layer  50 G includes a halogen-containing protecting layer. The first protecting layer  50 G may include a halogen-free protecting layer, i.e., a protecting layer that contains substantially no halogen. 
     As shown in  FIG. 3F , the first sacrificial layer  30  is removed. The first sacrificial layer  30  may be removed by a lift-off process. The first sacrificial layer  30  may be removed together with an overlying portion of the first light-emitting layer  40 G that is over the first sacrificial layer  30  and an overlying portion of the first protecting layer  50 G that is over the first sacrificial layer  30 . In other words, the first sacrificial layer  30  is washed out simultaneously with the overlying portion of the first light-emitting layer  40 G and the overlying portion of the first protecting layer  50 G that are on the surface of the first sacrificial layer  30 . 
     As defined herein, use of the term “simultaneously” indicates that the first sacrificial layer  30 , the overlying portion of the first light-emitting layer  40 G and the overlying portion of the first protecting layer  50 G may be removed in a single lift-off process. Alternatively, the first sacrificial layer  30 , the overlying portion of the first light-emitting layer  40 G and the overlying portion of the first protecting layer  50 G may be removed in different steps of the lift-off process. 
     Accordingly, a portion of the first light-emitting layer  40 G and a portion of the first protecting layer  50 G that are within the first opening  32  remain in place and substantially cover the first sub-pixel  12 G. The remaining portion of the first light-emitting layer  40 G and the remaining portion of the first protecting layer  50 G are respectively configured as the first patterned light-emitting layer  40 G′ and the first patterned protecting layer  50 G′. Further, the first patterned light-emitting layer  40 G′ and the first patterned protecting layer  50 G′ together are configured as the first patterned structure P 1  As a result, a pixel structure with the first patterned structure P 1  on the first sub-pixel  12 G is formed. 
     Referring to  FIGS. 3G to 3K , operations similar to those illustrated in  FIGS. 3B to 3F  can be repeated to form a differently-colored light-emitting layer. As shown in  FIG. 3G , a second sacrificial layer  60  is formed over the substrate  10 . The second sacrificial layer  60  covers the first patterned structure P 1  on the first sub-pixel  12 G. The second sacrificial layer  60  may have the same composition as the first sacrificial layer  30 . In some embodiments, the second sacrificial layer  60  may have a composition different from that of the first sacrificial layer  30 . In the present embodiment, the second sacrificial layer  60  includes a photosensitive layer. 
     As shown in  FIG. 3H , the second sacrificial layer  60  is patterned to form a second opening  62  exposing the second sub-pixel  12 R. Specifically, the second sacrificial layer  60  is patterned by a photolithography process. The second sacrificial layer  60  may be heated to a predetermined temperature, then exposed to radiation of a designated wavelength. After exposure, the second sacrificial layer  60  is rinsed in a solution for development. A portion of the second sacrificial layer  60  is removed and the remaining portion is left substantially covering the first patterned structure P 1  in the first sub-pixel  12 G. 
     The first patterned protecting layer  50 G′ may be configured to protect the first patterned light-emitting layer  40 G′ during the photolithography process for forming the second opening  62 . In some embodiments, the first patterned protecting layer  50 G′ includes UV-absorbing materials. The first patterned protecting layer  50 G′ may absorb the radiation such that the first patterned light-emitting layer  40 G′ incurs less damage. In some embodiments, the first patterned protecting layer  50 G′ includes heat-absorbing materials. The first patterned protecting layer  50 G′ may absorb the heat such that the first patterned light-emitting layer  40 G′ undergoes less temperature variation. 
     Referring to  FIG. 3I , a second light-emitting layer  40 R is formed over the second sacrificial layer  60  and on the second sub-pixel  12 R through the second opening  62  of the second sacrificial layer  60 . The second light-emitting layer  40 R may be configured to display an image of a second color. In some embodiments, the second light-emitting layer  40 R may be configured to display the color red. 
     As shown in  FIG. 3J , a second protecting layer  50 R is formed over the second sacrificial layer  60  and on the second sub-pixel  12 R through the second opening  62  of the second sacrificial layer  60 . In some embodiments, the second protecting layer  50 R is formed over the second light-emitting layer  40 R. The second protecting layer  50 R may be configured to protect the underlying second light-emitting layer  40 R. In some embodiments, the second protecting layer  50 R includes UV-absorbing materials. In some embodiments, the second protecting layer  50 R includes a halogen-containing protecting layer. The second protecting layer  50 R may include a halogen-free protecting layer, i.e., a protecting layer that contains substantially no halogen. 
     Referring to  FIG. 3K , the second sacrificial layer  60  is removed. The second sacrificial layer  60  may be removed by a lift-off process. The second sacrificial layer  60  may be removed together with an overlying portion of the second light-emitting layer  40 R that is over the second sacrificial layer  60  and an overlying portion of the second protecting layer  50 R that is over the second sacrificial layer  60 . In other words, the second sacrificial layer  60  is washed out simultaneously with the overlying portion of the second light-emitting layer  40 R and the overlying portion of the second protecting layer  50 R that are on the surface of the second sacrificial layer  60 . 
     As defined herein, use of the term “simultaneously” indicates that the second sacrificial layer  60 , the overlying portion of the second light-emitting layer  40 R and the overlying portion of the second protecting layer  50 R may be removed in a single lift-off process. Alternatively, the second sacrificial layer  60 , the overlying portion of the second light-emitting layer  40 R and the overlying portion of the second protecting layer  50 R may be removed in different steps of the lift-off process. 
     Accordingly, a portion of the second light-emitting layer  40 R and a portion of the second protecting layer  50 R that are within the second opening  62  remain in place and substantially cover the second sub-pixel  12 R. The remaining portion of the second light-emitting layer  40 R and the remaining portion of the second protecting layer  50 R are respectively configured as the second patterned light-emitting layer  40 R′ and the second patterned protecting layer  50 R′. Further, the second patterned light-emitting layer  40 R′ and the second patterned protecting layer  50 R′ together are configured as the second patterned structure P 2 . 
     The first patterned protecting layer  50 G′ may be configured to protect the first patterned light-emitting layer  40 G′ during the lift-off process for removing the second sacrificial layer  60 . In some embodiments, the first patterned protecting layer  50 G′ includes materials that are resistant to lift-off agents. The first patterned protecting layer  50 G′ may prevent the lift-off agents from interacting with the first patterned light-emitting layer  40 G′ during the lift-off process. As a result, a pixel structure with the first patterned structure P 1  on the first sub-pixel  12 G and the second patterned structure P 2  on the second sub-pixel  12 R is formed. 
     Referring to  FIG. 3L , the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ are respectively removed from the first patterned structure P 1  and the second patterned structure P 2 . The first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′ are left substantially in the first sub-pixel  12 G and the second sub-pixel  12 R, respectively. It is worth noting that the first patterned protecting layer  50 G′ is not removed until the second patterned structure P 2  is formed. The first patterned protecting layer  50 G′ is designed to be removed together with the second patterned protecting layer  50 R′. Thus, the procedures of the method for manufacturing the electroluminescent device are simplified and cost-effective. 
     In some embodiments, a thickness of the first patterned protecting layer  50 G′ is substantially the same as a thickness of the second patterned protecting layer  50 R′. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be simultaneously removed from the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′, respectively. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be removed by an etching process, but the present disclosure is not limited thereto. 
     As defined herein, use of the term “simultaneously” indicates that the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be removed in a single etching process. Alternatively, the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be removed in different steps of the etching process. In some embodiments, the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be removed at the same time. 
     In some embodiments, the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ are soluble in an etchant, and the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′ are insoluble or less soluble in the etchant. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be removed without causing damage to the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′. In some embodiments, the etchant includes halogen-containing solvents. In some embodiments, the etchant may include halogen-free solvents, i.e., solvents that contain substantially no halogen. 
     In some embodiments, an etch selectivity of the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ are greater than that of the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be etched away without etching the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′. In some embodiments, the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ include fluorine materials. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be free of fluorine, i.e., containing substantially no fluorine. 
     The first carrier-injection layer  22  and the first carrier-transportation layer  24  may be formed prior to the forming of the first light-emitting layer  40 G. The second carrier-injection layer  28  and the second carrier-transportation layer  26  may be formed by the same patterning process as that used to form the first light-emitting layer  40 G or the second light-emitting layer  40 R, but are not limited thereto. In some embodiments, the second carrier-injection layer  28  and the second carrier-transportation layer  26  may be formed prior to the forming of the first protecting layer  50 G or the second protecting layer  50 R. The second carrier-injection layer  28  and the second carrier-transportation layer  26  may be formed after the removing of the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′. 
     The second electrode  15  may be formed on the substrate  10  prior to the removing of the first sacrificial layer  30  or the second sacrificial layer  60 . The second electrode  15  may be formed by the same patterning process as that used to form the first light-emitting layer  40 G or the second light-emitting layer  40 R, but is not limited thereto. In some embodiments, the second electrode  15  may be formed on the substrate  10  after the removing of the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′. 
     Although not intended to be limiting, the present disclosure provides protecting layers  50 G and  50 R for the temporary protection of vulnerable organic light-emitting layers  40 G and  40 R. The protecting layers  50 G and  50 R covering the organic light-emitting layers  40 G and  40 R protect the organic light-emitting layers  40 G and  40 R. Thus, the organic light-emitting layers  40 G and  40 R incur less damage during the photolithography process. The method of manufacturing an electroluminescent device simplifies the fabrication procedures by removing the protecting layers  50 G and  50 R in a single step. Accordingly, reduced manufacturing costs can be expected. Therefore, a high-resolution electroluminescent device may be formed in a cost-effective manner. 
     Other alternatives or embodiments may be used without departure from the spirit and scope of the present disclosure. With continued reference to  FIG. 3K ,  FIGS. 4A to 4F  illustrate a method of manufacturing an electroluminescent device according to some embodiments of the present disclosure. In the present embodiment, the number of sub-pixels in one pixel  12  is three, but is not limited thereto. 
     Referring to  FIGS. 4A to 4F , operations similar to those illustrated in  FIGS. 3B to 3F  can be repeated to form a light-emitting layer that emits light of a different color. As shown in  FIG. 4A , a third sacrificial layer  70  is formed over the substrate  10 . The second sacrificial layer  60  covers the first patterned structure P 1  in the first sub-pixel  12 G and the second patterned structure P 2  in the second sub-pixel  12 R. The third sacrificial layer  70  may have the same composition as the first sacrificial layer  30 . In some embodiments, the third sacrificial layer  70  includes a photosensitive layer. 
     As shown in  FIG. 4B , the third sacrificial layer  70  is patterned to form a third opening  72  exposing the third sub-pixel  12 B. Specifically, the third sacrificial layer  70  is patterned by a photolithography process as described above. The third sacrificial layer  70  may be heated to a predetermined temperature, then exposed to radiation of a designated wavelength. After exposure, the third sacrificial layer  70  is rinsed in a solution for development. A portion of the third sacrificial layer  70  is removed and the remaining portion is left substantially covering the first patterned structure P 1  in the first sub-pixel  12 G and the second patterned structure P 2  in the second sub-pixel  12 R. 
     The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be respectively configured to protect the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′ during the photolithography process for forming the third opening  72 . In some embodiments, the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ include UV-absorbing materials. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may absorb the radiation such that the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′ incur less damage. 
     Referring to  FIG. 4C , a third light-emitting layer  40 B is formed over the third sacrificial layer  70  and on the third sub-pixel  12 B through the third opening  72  of the third sacrificial layer  70 . The third light-emitting layer  40 B may be configured to display an image of a third color. In some embodiments, the third light-emitting layer  40 B may be configured to display the color blue. 
     As shown in  FIG. 4D , a third protecting layer  50 B is formed over the third sacrificial layer  70  and on the third sub-pixel  12 B through the third opening  72  of the third sacrificial layer  70 . In some embodiments, the third protecting layer  50 B is formed over the third light-emitting layer  40 B. The third protecting layer  50 B may be configured to protect the underlying third light-emitting layer  40 B. In some embodiments, the third protecting layer  50 B includes UV-absorbing materials. In some embodiments, the third protecting layer  50 B includes a halogen-containing protecting layer. The third protecting layer  50 B may include a halogen-free protecting layer, i.e., a protecting layer containing substantially no halogen. 
     Referring to  FIG. 4E , the third sacrificial layer  70  is removed. The third sacrificial layer  70  may be removed by a lift-off process. The third sacrificial layer  70  may be removed together with an overlying portion of the third light-emitting layer  40 B that is over the third sacrificial layer  70  and an overlying portion of the third protecting layer  50 B that is over the third sacrificial layer  70 . In other words, the third sacrificial layer  70  is washed out simultaneously with the overlying portion of the third light-emitting layer  40 B and the overlying portion of the third protecting layer  50 B that are on the surface of the third sacrificial layer  70 . 
     Accordingly, a portion of the third light-emitting layer  40 B and a portion of the third protecting layer  50 B that are within the third opening  72  remain in place and substantially cover the third sub-pixel  12 B. The remaining portion of the third light-emitting layer  40 B and the remaining portion of the third protecting layer  50 B are respectively configured as the third patterned light-emitting layer  40 B′ and the third patterned protecting layer  50 B′. Further, the third patterned light-emitting layer  40 B′ and the third patterned protecting layer  50 B′ together are configured as the third patterned structure P 3 . 
     The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ may be respectively configured to protect the first patterned light-emitting layer  40 G′ and the second patterned light-emitting layer  40 R′ during the lift-off process for removing the third sacrificial layer  70 . As a result, a pixel structure with the first patterned structure P 1  on the first sub-pixel  12 G, the second patterned structure P 2  on the second sub-pixel  12 R and the third patterned structure P 3  on the third sub-pixel  12 B is formed. 
     Referring to  FIG. 4F , the first patterned protecting layer  50 G′, the second patterned protecting layer  50 R′ and the third patterned protecting layer  50 B′ are respectively removed from the first patterned structure P 1 , the second patterned structure P 2  and the third patterned structure P 3 . The first patterned light-emitting layer  40 G′, the second patterned light-emitting layer  40 R′ and the third patterned light-emitting layer  40 B′ are left substantially in the first sub-pixel  12 G, the second sub-pixel  12 R and the third sub-pixel  12 B, respectively. It is worth noting that the first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ are not removed until the third patterned structure P 3  is formed. The first patterned protecting layer  50 G′ and the second patterned protecting layer  50 R′ are designed to be removed together with the third patterned protecting layer  50 B′. Thus, the procedures of the method for manufacturing the electroluminescent device are simplified and cost-effective. 
     Although not intended to be limiting, the embodiments of the present disclosure provide significant improvements to the methods for manufacturing electroluminescent devices. The present disclosure provides a protecting layer for the sensitive organic light-emitting layer. The protecting layer prevents the organic light-emitting layer from damage during the photolithography process. The method overcomes process constraints of the photolithography process by minimizing the process procedures. Further, less damage is incurred by the light-emitting layer and reduced manufacturing cost can be expected. Therefore, a high-resolution electroluminescent device is formed in a cost-effective manner. 
     As used herein, the singular terms “a,” “an,” and “the” may include a plurality of referents unless the context clearly dictates otherwise. 
     As used herein, the terms “approximately,” “substantially,” “substantial” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to +10% of that numerical value, such as less than or equal to ±5%, less than or equal to 4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to 1%, less than or equal to 0.5%, less than or equal to 0.1%, or less than or equal to 0.05%. For example, two numerical values can be deemed to be “substantially” the same or equal if the difference between the values is less than or equal to ±10% of an average of the values, such as less than or equal to +5%, less than or equal to 4%, less than or equal to 3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to 0.5%, less than or equal to 0.1%, or less than or equal to 0.05%. For example, “substantially” parallel can refer to a range of angular variation relative to 0° that is less than or equal to ±10°, such as less than or equal to 5°, less than or equal to 4°, less than or equal to 3°, less than or equal to 2°, less than or equal to 1°, less than or equal to +0.5°, less than or equal to ±0.1°, or less than or equal to 0.05°. For example, “substantially” perpendicular can refer to a range of angular variation relative to 90 that is less than or equal to 10°, such as less than or equal to +5°, less than or equal to 4°, less than or equal to 3°, less than or equal to 2°, less than or equal to 10, less than or equal to 0.5°, less than or equal to 0.1°, or less than or equal to +0.05°. 
     Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range were explicitly specified. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.