Abstract:
The present invention discloses a novel purifying method for the organic optoelectronic material. More specifically the present invention relates to a purifying method for organic electroluminescent (herein referred to as organic EL) material, organic photovoltaics (herein referred to as OPV) material and organic thin-film transistor (herein referred to as OTFT) material. The organic optoelectronic device use the organic optoelectronic material can lower driving voltage, prolong half-lifetime and improve performance.

Description:
FIELD OF INVENTION 
     The present invention generally relates to a novel purifying method for organic optoelectronic material. More specifically the present invention relates to a purifying method for organic electroluminescent (herein referred to as organic EL) material, organic photovoltaics (herein referred to as OPV) material and organic thin-film transistor (herein referred to as OTFT) material. The organic optoelectronic device use the organic optoelectronic material can improve performance. 
     BACKGROUND OF THE INVENTION 
     Organic optoelectronic material has been developed for several decades. Recently the organic optoelectronic material are widely put in use in organic optoelectronic devices, such as organic EL device, OPV device and OTFT device have attracted significant attention for industries practice use due to their potential application for flat-panel and flexible display, solid-state lighting, solar energy storage, etc. Organic EL device have many advantages such as self-emitting, wider viewing angles, faster response speeds and highly luminescence. Their simpler fabrication and capable of giving clear display comparable with LCD, making organic EL device an industry display of choice and has stepped into commercialization. OPV has been considered as a highly growing trend for green energy technology because of its low cost, simple preparation and large area capability. The conversion efficiency of OPV had reached to the practical application. OTFT has grown into a hotspot in organic electronics as it also possesses the merits of low cost, flexibility, low temperature processing and large area capability. And its performance is already comparable to that of the amorphous silicon based thin film transistors. 
     However, there are still many technical problems remaining to be solved in organic optoelectronic devices, such as material impurity, material instability, low power efficiency, short life time, etc., which hindered the commercialization of organic optoelectronic devices. Especially the purity of organic optoelectronic materials need to be improved. Some metal ions, halide ions, dyes, pigments, chromatophores and other residues will appear and dying the organic optoelectronic material during synthesis procedure. These impurities exert an influence to characteristic of organic optoelectronic devices like lower efficiency, shorter half-life time and raise applied driving voltage. Therefore the purifying method for organic optoelectronic material becomes critical technology to organic optoelectronic devices. After finishing organic synthesis procedures, there are some purifying methods to improve the purity like crystallization, recrystallization, column chromatograph, sublimation, etc. Due to many organic optoelectronic materials could not be dissolved in organic solvent, chemical purifying method could not effectual purify these organic optoelectronic materials. Sublimation methods are suitable to purify non-dissolved organic optoelectronic materials. But some metal ions, halide ions, dying colour, pigments, chromatophores, etc., which still involved in organic optoelectronic materials always be bring out via sublimation vapor. These impurities could not be effectual eliminated via sublimation process and also will be bring out during deposition process when fabricate the organic optoelectronic device. The purifying method of sublimation process and deposition process need to be improved for organic optoelectronic material for industrial practice use. 
     In the present invention, for the purpose to improve the purity of organic optoelectronic material we embedded decolorized material or deionized material (herein referred to as adsorbent) into sublimation process or deposition process to eliminate these impurities. These impurities including metal ions, halide ions, dying colour, pigments, chromatophores, etc., which are absorbed and eliminated when sublimation vapor or deposition vapor passed through the adsorbent to get high purity of organic optoelectronic material. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a purifying method for organic optoelectronic material and their use for organic optoelectronic device are provided. The purifying method can eliminate impurities like as metal ions, halide ions, dying colour, pigments, chromatophores, etc. during sublimation process or deposition process. The purifying method for organic optoelectronic material can prolong half-life time, lower driving voltage and power consumption for organic optoelectronic device. 
     An object of the present invention is to provide a purifying method to eliminate impurities, then produce high purity of organic optoelectronic material. 
     Another object of the present invention is to apply the high purified organic optoelectronic material to prolong half-life time, lower driving voltage and power consumption for organic optoelectronic (Organic EL, OPV, OTFT) device. 
     The present invention has the economic advantages for industrial practice. Accordingly, the present invention discloses a purifying method for organic optoelectronic material is disclosed as following: 
     1. Adsorbent is mixed with organic optoelectronic material and put the mixed material on a quartz boat, then is placed into a quartz tube for sublimation process (See  FIG. 2 ). 
     2. Adsorbent is embedded into a double-layer filter plate and cover upon a an quartz boat wherein organic optoelectronic material is loaded in, then the quartz boat is placed into a quartz tube for sublimation process (See  FIG. 3 ). 
     3. Adsorbent is embedded into a double-layer filter cartridges and place on two side of an small quartz tube wherein organic optoelectronic material is loaded in, then the small quartz tube is placed into a quartz tube for sublimation process (See  FIG. 4 ). 
     4. Adsorbent is mixed with organic optoelectronic material and put the mixed material into a container, then is placed on a heat source of deposition machine for deposition process (See  FIG. 5 ). 
     5. Adsorbent is embedded into a double-layer filter plate and cover upon a container wherein organic optoelectronic material is loaded in, then is placed on a heat source of deposition machine for deposition process (See  FIG. 6 ). Wherein the adsorbent are selected from active carbon, celite, silica gel, zeolite, activated alumina, carbon molecular sieves, molecular sieves, etc.
 
The organic optoelectronic material is consisting of Organic EL material, OPV material, OTFT material which are used in organic optoelectronic device. The weight ratio of the adsorbent and the organic optoelectronic material is selected from 1:100 to 100:1.
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       FIG.  1 - a  show the diagram of sublimation process for equipment including a quartz boat  102  which is used for loading organic optoelectronic material and/or adsorbent, a quartz tube  103  which is used for embedding the quartz boat  102  and collect sublimed product, a tunnel furnace  104  which is used for heating the quartz tube  103  and keep it on an equilibrium temperature and a high vacuum pump  105 , which can keep this system under 10 −6  Torr, and this sublimation equipment can sublime organic optoelectronic material. FIG.  1 - b  show the diagram of deposition equipment including vacuum chamber  106 , a container  107  which is used for loading organic optoelectronic material and/or adsorbent, and a high vacuum pump  108 , which can keep this system under 10 −7  Torr, and this deposition equipment can evaporate organic optoelectronic material. 
         FIG. 2  show the diagram of a quartz boat  202  which loading the mixed material  203  including different weight ratio of the adsorbent and the organic optoelectronic material. 
         FIG. 3  show the diagram of a quartz boat  302  which loading the organic optoelectronic material  303 , then a double-layer filter plate  304  which cover upon the quartz boat  302 . 
         FIG. 4  show the diagram of a quartz tube  402  which loading the organic optoelectronic material  403 , then a double-layer filter cartridges  404  which place on two side of the quartz tube  402 . 
         FIG. 5  show the diagram of a container  502  which loading the mixed material  503  including different weight ratio of the adsorbent and the organic optoelectronic material. 
         FIG. 6  show the diagram of a container  602  which loading the mixed including different weight ratio of the adsorbent and the organic optoelectronic material  603 , then a double-layer filter plate  604  which cover upon the container  602 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     What probed into the invention is a purifying method for organic optoelectronic material. Detailed descriptions of the purifying method, equipment, procedures and organic optoelectronic material will be provided in the following to make the invention thoroughly understood. Obviously, the application of the invention is not confined to specific details familiar to those who are skilled in the art. On the other hand, the common purifying method and procedures that are known to everyone are not described in details to avoid unnecessary limits of the invention. Some preferred organic optoelectronic material can be purified by the purifying method of the present invention will now be described in greater detail in the following. However, it should be recognized that the present invention can be practiced in a wide range of other organic optoelectronic materials besides those explicitly described, that is, this invention can also be applied extensively to other organic optoelectronic materials and the scope of the present invention is expressly not limited except as specified in the accompanying claims. 
     DEFINITION 
     In a first embodiment of the present invention, the present invention discloses a purifying method for organic optoelectronic material is disclosed as following: 
     1. Adsorbent is mixed with organic optoelectronic material and put the mixed material on a quartz boat, then is placed into a quartz tube for sublimation process (See  FIG. 2 ). 
     2. Adsorbent is embedded into a double-layer filter plate and cover upon a quartz boat wherein organic optoelectronic material is loaded in, then the quartz boat is placed into a quartz tube for sublimation process (See  FIG. 3 ). 
     3. Adsorbent is embedded into a double-layer filter cartridges and place on two side of an small quartz tube wherein organic optoelectronic material is loaded in, then the small quartz tube is placed into a quartz tube for sublimation process (See  FIG. 4 ). 
     4. Adsorbent is mixed with organic optoelectronic material and put the mixed material into a container, then is placed on a heat source of deposition machine for deposition process (See  FIG. 5 ). 
     5. Adsorbent is embedded into a double-layer filter plate and cover upon a container wherein organic optoelectronic material is loaded in, then is placed on a heat source of deposition machine for deposition process (See  FIG. 6 ). Wherein the adsorbent are selected from active carbon, celite, silica gel, zeolite, activated alumina, carbon molecular sieves, molecular sieves, etc.
 
The organic optoelectronic material is consisting of Organic EL material, OPV material, OTFT material which are used in organic optoelectronic device. The weight ratio of the adsorbent and the organic optoelectronic material is selected from 1:100 to 100:1.
 
     Some examples of organic optoelectronic material use the purifying method of the present invention are listed as following: 
     Organic Electroluminescent Material 
     
       
                 
         
             
             
         
      
       
                 
         
             
             
         
       
       
                 
         
             
             
         
       
     
     
       
                 
         
             
             
         
      
       
                 
         
             
             
         
       
       
                 
         
             
             
         
       
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
       
                 
         
             
             
         
       
     
     
       
                 
         
             
             
         
      
       
                 
         
             
             
         
       
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
     
     
       
                 
         
             
             
         
      
       
                 
         
             
             
         
       
     
     
       
                 
         
             
             
         
      
     
     Example 1 
     Purification for Compound Dipyrazino[2,3-f:2,3-]Quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) 
     20 g of brown powder of HAT-CN was mixed with 10 g of active carbon and put into quartz boat  202  (see  FIG. 2 ) for sublimation process. Keep the tunnel furnace at a constant temperature (320° C.) for 8 hours. After cooling down to room temperature, scrape out purified HAT-CN from ventral quartz tube to get 8.3 g of white crystal of HAT-CN-Purified, Yield=41.5%. 
     Example 2 
     Purification for Compound 9,10-di(naphthalen-2-yl)anthracene (AND) 
     35 g of yellow powder of ADN was mixed with 20 g of celite and put into quartz boat  302  (see  FIG. 3 ) for sublimation process. Keep the tunnel furnace at a constant temperature (265° C.) for 3 hours. After cooling down to room temperature, scrape out purified AND from ventral quartz tube to get 31 g of light yellow crystal of ADN-Purified, Yield=88.5%. 
     General Method of Producing Organic EL Device 
     ITO-coated glasses with 9˜12 ohm/square in resistance and 120˜160 nm in thickness are provided (hereinafter ITO substrate) and cleaned in a number of cleaning steps in an ultrasonic bath (e.g. detergent, deionized water). Before vapor deposition of the organic layers, cleaned ITO substrates are further treated by UV and ozone. All pre-treatment processes for ITO substrate are under clean room (class  100 ). 
     These organic layers are applied onto the ITO substrate in order by vapor deposition in a high vacuum unit (10 −7  Torr), such as: resistively heated quartz boats. The thickness of the respective layer and the vapor deposition rate (0.1˜0.3 nm/sec) are precisely monitored or set with the aid of a quartz-crystal monitor. It is also possible, as described above, for individual layers to consist of more than one compound, i.e. in general a host material doped with a guest material. This is achieved by co-vaporization from two or more sources. 
     Dipyrazino[2,3-f:2,3-]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) is used as hole injection layer in this organic EL device. N,N-Bis(naphthalene-1-yl)-N,N-bis(phenyl)-benzidine (NPB) is most widely used as the hole transporting layer and 4,7-Diphenyl-2,9-bis(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-1,10-phenanthroline (LT-N8001, U.S. Pat. No. 7,754,348) is used as electron transporting material in organic EL device for its high thermal stability and long life-time than BPhen/BCP. 9,10-di(naph thalene-2-yl)anthracene (ADN, U.S. Pat. No. 5,935,721) and 10,10-Dimethyl-12-(4-(pyren-1-yl)phenyl)-1 OH-indeno[1,2-b]triphenylene (PT-302, US20140175384) are used as emitting host and (E)-6-(4-(diphenylamino)styryl)-N,N-diphenyl naphthalen-2-amine (D1) is used as guest. 4,7-Diphenyl-2,9-bis(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-1,10-phenanthroline (LT-N8001, U.S. Pat. No. 7,754,348). The above organic EL materials for producing standard organic EL device in this invention are shown its chemical structure as following: 
     
       
                 
         
             
             
         
      
       
                 
         
             
             
         
       
     
     A typical organic EL device consists of low work function metals, such as Al, Mg, Ca, Li and K, as the cathode by thermal evaporation, and the low work function metals can help electrons injecting the electron transporting layer from cathode. In addition, for reducing the electron injection barrier and improving the organic EL device performance, a thin-film electron injecting layer is introduced between the cathode and the electron transporting layer. Conventional materials of electron injecting layer are metal halide or metal oxide with low work function, such as: Li, LiF, MgO, or Li 2 O. 
     On the other hand, after the organic EL device fabrication, EL spectra and CIE coordination are measured by using a PR650 spectra scan spectrometer. Furthermore, the current/voltage, luminescence/voltage and yield/voltage characteristics are taken with a Keithley 2400 programmable voltage-current source. The above-mentioned apparatuses are operated at room temperature (about 25° C.) and under atmospheric pressure. 
     Example 3 
     Using a procedure analogous to the above mentioned general method, fluorescent blue-emitting organic EL device having the following device structure were produced: ITO/HAT-CN (20 nm) or HAT-CN-Purified/NPB (130 nm)/fluorescent blue host (PT-312) doped 5% D1 (35 nm)/LT-N8001 (30 nm)/LiF (0.5 nm)/Al (160 nm). The I-V-B and half-life time of fluorescent blue-emitting OLED device testing report as Table 1, The half-life time is defined that the initial luminance of 1000 cd/m 2  has dropped to half. 
     
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Hole 
                 Fluo- 
                   
                   
                   
                 Half-lifetime(hour) 
               
               
                 injection 
                 rescent 
                 Voltage 
                 Yield 
                   
                 Initial luminance = 
               
               
                 material 
                 blue host 
                 (V) 
                 (cd/A) 
                 CIE(y) 
                 1000(cd/m 2 ) 
               
               
                   
               
             
             
               
                 HAT-CN 
                 PT-312 
                 5.4 
                 6.0 
                 0.188 
                 220 
               
               
                 HAT-CN- 
                 PT-312 
                 4.8 
                 6.3 
                 0.188 
                 550 
               
               
                 Purified 
               
               
                   
               
             
          
         
       
     
     Example 4 
     Using a procedure analogous to the above mentioned general method, fluorescent blue-emitting organic EL device having the following device structure were produced: ITO/HAT-CN (20 nm)/NPB (60 nm)/AND or AND-purified doped 5% D1 (35 nm)/LT-N8001 (30 nm)/LiF (0.5 nm)/Al (160 nm). The I-V-B and half-life time of fluorescent blue-emitting OLED device testing report as Table 2, The half-life time is defined that the initial luminance of 1000 cd/m 2  has dropped to half. 
     
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Hole 
                 Fluo- 
                   
                   
                   
                 Half-lifetime(hour) 
               
               
                 injection 
                 rescent 
                 Voltage 
                 Yield 
                   
                 Initial luminance = 
               
               
                 material 
                 blue host 
                 (V) 
                 (cd/A) 
                 CIE(y) 
                 1000(cd/m 2 ) 
               
               
                   
               
             
             
               
                 HAT-CN 
                 ADN 
                 7.8 
                 2.9 
                 0.152 
                 150 
               
               
                 HAT-CN 
                 AND- 
                 6.9 
                 3.2 
                 0.153 
                 280 
               
               
                   
                 Purified 
               
               
                   
               
             
          
         
       
     
     In the above preferred embodiments, we show that the material HAT-CN-Purified (From Example 1) and AND-Purified (From Example 2) used as fluorescent blue-emitting organic EL device than comparable example HAT-CN and ADN without using purifying method in the present invention with higher half-life time and practical operation durability. Under the same Luminance (cd/m 2 ), lower driving voltage comparable example HAT-CN and ADN have also been achieved at 1000 cd/m 2  using the mentioned material purified method from the present invention for blue-emitting organic EL devices. 
     To sum up, the present invention discloses a purifying method for organic optoelectronic material and their use for organic optoelectronic device are provided. The purifying method for organic optoelectronic material can prolong half-life time, lower driving voltage and power consumption for organic optoelectronic device.