Abstract:
An organic light emitting diode (OLED) package includes a substrate, an OLED die mounted on the substrate and an encapsulation layer encapsulating the OLED die. The OLED package further includes a protecting layer formed on the OLED die. The encapsulation layer has a multi-layered structure and is deposited on the protecting layer. Refractive indexes of a cathode of the OLED die, the protecting layer and the encapsulation layer are gradually decreased in the sequence. A barrier layer for blocking moisture from entering the OLED package is formed on a bottom surface of the substrate by atomic layer deposition (ALD) method. The present disclosure also provides a method for manufacturing the OLED package.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a semiconductor emitting component and method for manufacturing the semiconductor, and more particularly, to an organic light emitting diode (OLED) and method for manufacturing the same. 
     2. Description of the Related Art 
     OLEDs have many advantages, such as light weight, thin thickness, multiple colors and low manufacturing cost, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness. Such advantages have promoted the wide use of the OLED in some illuminating device as a plane light source instead of traditional LED. 
     Due to luminescence properties of the OLED, oxygen or moisture in the air can easily affect the OLED and reduces a lifetime thereof; as such the OLED should be packaged before it is applied to the illuminating device. A conventional OLED package includes an OLED die and an encapsulation layer deposited on the OLED die. However, in the process of packaging the OLED, stress generated by depositing the encapsulation is easily transferred to the OLED die, which causes the OLED to easily crack, thereby reducing the lifespan of the OLED package. 
     Therefore, it is desirable to provide an OLED package and method for manufacturing the OLED package which can obviate the disadvantages of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is a cross-sectional view of an OLED package in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view of an OLED die of the OLED package of  FIG. 1 . 
         FIG. 3  is a top view of the OLED package of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 to 3 , an OLED package  100  in accordance with an embodiment is provided. The OLED package  100  is a top emitting type package. The OLED package  100  includes a substrate  10 , a barrier layer  20  and a thin film transistor (TFT) array  30  arranged on the substrate  10 , an OLED die  40  arranged on the TFT array  30 , a protecting layer  50  arranged on the OLED die  40 , and an encapsulation layer  60  arranged on the protecting layer  50 . 
     Specifically, the substrate  10  is flexible and made of some plastic materials such as polyimide, polymer and so on. The substrate  10  includes a bottom surface  11  and a top surface  12  opposite to the bottom surface  11 . 
     The barrier layer  20  is arranged on the bottom surface  11  of the substrate for preventing the moisture in the air from entering the OLED package  100 . The barrier layer  20  is a thin film made of some materials such as oxide, nitride, fluoride, metal or organic materials and so on. In this embodiment, the barrier layer  20  is made of aluminum oxide (Al 2 O 3 ). 
     The TFT array  30  is arranged on the top surface  12  of the substrate  10 . The TFT array  30  electrically connects with the OLED die  40  for controlling luminous state of the OLED die  40 . 
     Referring to  FIG. 2 , in this embodiment, the OLED die  40  includes an anode  41  arranged on the TFT array  30 , an active layer  42  arranged on the anode  41 , and a cathode  43  arranged on the active layer  42 . That is, the active layer  42  is sandwiched between the anode  41  and the cathode  43 . The anode  41  and the cathode  43  electrically connect with the TFT. The anode  41  is reflective for reflecting part of light generated by the active layer  42  toward the cathode  43 . The cathode  43  is semitransparent. A thickness of the cathode  43  is substantially 10 nanometers. The active layer  42  is a transparent semiconductor film. 
     The protecting layer  50  is arranged on the cathode  43  of the OLED die  40  and covers side surfaces of the OLED  40  for protecting the OLED die  40  from being destructed by stress generated in the depositing process of the encapsulation layer  60 . The protecting layer  50  is a translucent film, and the protecting layer  50  is made of some materials such as silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (Al 2 O 3 ), polymer, etc. Preferably, a refractive index of the protecting layer  50  is smaller than that of the cathode  43 . 
     The encapsulation layer  60  is arranged on the protecting layer  50 . The encapsulation layer  60  is a translucent, multi-layered structure. The encapsulation layer  60  includes a light inputting layer  61  arranged on the protecting layer  50 , a buffer layer  62  arranged on the light inputting layer  61 , and a light outputting layer  63  arranged on the buffer layer  62 . The light inputting layer  61  and the light outputting layer  63  are made of same material such as plastic, resin, etc. The buffer layer  62  is sandwiched between the light inputting layer  61  and the light outputting layer  63 . The material of the buffer layer  62  is different from that of the light inputting layer  61  and the light outputting layer  63 . The buffer layer  62  buffers a flexure stress generated in the encapsulation layer  60  to strengthen a stability of the encapsulation layer  60 . The buffer layer  62  is made of some materials such as silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (Al 2 O 3 ), polymer, etc. Preferably, a refractive index of the encapsulation layer  60  is smaller than that of the protecting layer  50 . In this embodiment, the refractive index of the encapsulation layer  60  ranges from 1.46 to 1.9. Alternatively, the encapsulation layer  60  can include a plurality of buffer layers  62  therein. The refractive index of each of the plurality of buffer layers  62  is substantially similar that of the light inputting layer  61  and the light outputting layer  62 . The difference between the refractive indexes of the multiple encapsulation layer  60  and the protecting layer  50  increases a light extraction and accordingly a brightness of light radiated by the OLED package  100 . 
     When the OLED package  100  works, since the anode  41  and the cathode  43  of the OLED die  40  electrically connect with the TFT array  30 , electrons inside the cathode  43  will be captured by electric holes inside the anode  41  under excitation of an electric field; photons are emitted in the form of light from the active layer  42  where the combinations of the electrons and the electric holes occur. The light generated by the LED die  40  successively passes through the cathode  43  and the protecting layer  50 , and enters the encapsulation layer  60  via the light inputting layer  61  and finally radiates out via the light outputting layer  63 . 
     Since a barrier layer  20  is arranged on the bottom surface  11  of the substrate  10 , the protecting layer  50  is arranged between the OLED die  40  and the encapsulation layer  60 , and a buffer layer  62  is sandwiched between the light inputting layer  61  and the light outputting layer  63 , a stability of the OLED package  100  is greatly improved. Correspondingly, the OLED die  40  is protected from being damaged, and a lifetime of the OLED package  100  is prolonged. 
     In addition, since the refractive index gradually decreases in a direction of from the cathode  43  to the light outputting layer  63 , the light output of the OLED package  100  is increased. In other words, a smaller current can be applied to the OLED die to drive the OLED die for generating the required illumination, compared with current needed for driving the LED die in the conventional OLED package. It is appreciated by a person skilled in the art that an OLED die working under a smaller current can have the benefit of a longer lifetime. 
     The disclosure provides a method for manufacturing the OLED package  100  which includes following steps. 
     Firstly, the flexible substrate  10  is provided. The barrier layer  20  is plated on the bottom surface  11  of the substrate  10  by atomic layer deposition (ALD) method. The ALD method is a self-limiting method, i.e., the amount of film material deposited in each reaction cycle being constant. Due to the self-limiting characteristics of the ALD method, the barrier layer  20  can be very compact. Furthermore, the barrier layer  20  and the substrate  10  can be tightly connected to each other. Accordingly, the barrier layer  20  can form a good barrier for resisting moisture. Thus, the OLED package  100  is protected from moisture in the air to enter the OLED package  100 . 
     Secondly, the TFT array  30  is arranged on the top surface  12  of the substrate  10 . 
     Thirdly, the OLED die  40  is arranged on the TFT array  30 . Specifically, the anode  41  of the OLED die  40  is formed to rest on the TFT array  30 , and the anode  41  and the cathode  43  are electrically connected to the TFT array  30 . 
     Thereafter, the protecting layer  50  is plated on the cathode  43  and the protecting layer  50  covers the side surfaces of the OLED die  40 . An environmental resistance to moisture and temperature of the protecting layer  50  is better than that of the OLED  40 . Accordingly, the protecting layer  50  further protects the OLED  40  from damage from the surrounding environment. 
     Finally, the encapsulation layer  60  is deposited on the protecting layer  50 . Specifically, the light inputting layer  61 , the buffer layer  62  and the light outputting layer  63  are successively deposited on the protecting layer  50  by plasma enhanced chemical vapor deposition (PECVD) method, physical vapor deposition (PVD) method or sputter method. Since the encapsulation layer  60  and the OLED die  40  are separated by the protecting layer  50 , the high stress generated by depositing the encapsulation layer  60  will not be directly transmitted to the OLED die  40  and the OLED die  40  is protected by the protecting layer  50 . 
     Alternatively, a plurality of protecting layers  50  formed of different materials can be formed between the OLED die  40  and the encapsulation layer  60 . The protecting layers  50  are translucent films. In addition, a plurality of buffer layers  62  can be continuously deposited between the light inputting layer  61  and the light outputting layer  63 . Preferably, the buffer layers  62  are translucent films. 
     It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.