Use Of Transition Metal Carbene Complexes In Organic Light-Emitting Diodes (Oleds)

Abstract

The present invention relates to the use of transition metal-carbene complexes in organic light-emitting diodes (OLEDs), to a light-emitting layer, to a blocking layer for electrons or excitons, or to a blocking layer for holes, each comprising these transition metal-carbene complexes, to OLEDs comprising these transition metal-carbene complexes, to devices which comprise an inventive OLED, and to transition metal-carbene complexes.

1 . An uncharged transition metal-carbene complex of the general formula I  
     
       
         
         
             
             
         
       
       which is suitable for use in organic light-emitting diodes, where the variables are each defined as follows:  
       M is a metal atom selected from the group consisting of Co, Rh, Ir, Nb, Pd, Pt, Fe, Ru, Os, Cr, Mo, W, Mn, Re, Cu, Ag and Au in any oxidation state possible for the particular metal atom;  
       L is a mono- or dianionic ligand which may be mono- or bidentate;  
       K is an uncharged mono- or bidentate ligand selected from the group consisting of phosphines; phosphonates and derivatives thereof; arsenates and derivatives thereof; phosphites; CO; pyridines; nitriles, monoolefins and conjugated dienes which form a π-complex with M;  
       n is the number of carbene ligands, where n is at least 1 and the carbene ligands in the complex of formula I, when n>1, may be the same or different;  
       m is the number of ligands L, where m may be 0 or ≧1 and the ligands L, when m>1, may be the same or different;  
       q is the number of ligands K, where q may be 0 or ≧1 and the ligands K, when q>1, may be the same or different, 
 where the sum of n+m+q depends upon the oxidation state and coordination number of the metal atom m and upon the denticity and the charge of the ligands, with the condition that n is at least 1;  
 
       Do is a donor atom selected from the group consisting of N, O and S;  
       r is 1 when Do is N and O when Do is O or S;  
       Y 1 , Y 2  are each independently hydrogen, alkyl, aryl, heteroaryl or alkenyl; or 
 Y 1  and Y 2 , together with the carbon atoms to which they are bonded, form a six-membered aromatic ring which may comprise one or two nitrogen atoms, and is optionally fused to a further ring which is optionally fused and optionally comprises heteroatoms;  
 
       Y 3  is hydrogen or alkyl; or 
 Y 3  and Y 2 , together with the donor atom Do and the carbon atom to which Y 2  is bonded, form a five- or six-membered ring which, apart from the donor atom Do, may also comprise a further heteroatom selected from the group consisting of N, O and S;  
 
       A is a bridge having three or four atoms, of which one or two atoms may be heteroatoms and the remaining atoms are carbon atoms, so that the group  
       
         
           
           
               
               
           
         
       
        forms a five- or six-membered heteroaromatic ring or benzene ring, each of which is optionally substituted by substituents selected from the group consisting of alkyl, alkyloxy, alkylthio, aryl, aryloxy, arylthio, halogen, CN, CHO, alkylcarbonyl, arylcarbonyl, carboxyl, alkyloxycarbonyl, aryloxycarbonyl, hydroxysulfonyl, alkyloxysulfonyl, aryloxysulfonyl, NO 2  and NO, and optionally fused with a further ring which is optionally fused and optionally comprises heteroatoms, 
 where Y 1,  together with a group selected from chemical single bond, C(Y 4 ) 2 , C(O), O, S, S(O), SO 2  and NY 5 , may optionally form a two-membered bridge B to that carbon atom or heteroatom of the bridge A which is in the α-position to the carbon atom which is bonded to the nitrogen atom of the carbene unit of the carbene ligand; and  
 
       Y 4 , Y 5  are each independently hydrogen, alkyl, aryl or heteroaryl, and the two Y 4  groups in the C(Y 4 ) 2  bridge may be varied independently of one another.  
     
   
   
       2 . The complex of formula I as claimed in  claim 1 , wherein 
 M is selected from the group consisting of Rh, Ir, Pd, Pt, Ru and Os in any oxidation state possible for the particular metal atom.    
   
   
       3 . The complex of formula I as claimed in  claim 1 , wherein 
 n is at least 2 and the carbene ligands may be the same or different;    m is 0 or ≧1 and the ligands L, when m>1, may be the same or different; and    q is 0 or ≧1 and the ligands K, when q>1, may be the same or different.    
   
   
       4 . The complex of formula I as claimed in  claim 1 , wherein 
 n is at least 2 and the carbene ligands may be the same or different; and    m, q are each 0.    
   
   
       5 . The complex of formula I as claimed in  claim 1 , wherein 
 n is at least 2 and the carbene ligands are the same; and    m and q are each 0.    
   
   
       6 . An organic light-emitting diode comprising an uncharged transition metal-carbene complex of general formula I as claimed in  claim 1 .  
   
   
       7 . A process for preparing a transition metal-carbene complex of a formula I as claimed in  claim 1  by deprotonating a ligand precursor corresponding to the particular carbene ligand and subsequently or simultaneously reacting it with a suitable metal complex comprising the desired metal.  
   
   
       8 . An OLED comprising at least one transition metal-carbene complex of formula I as claimed in  claim 1 .  
   
   
       9 . A light-emitting layer comprising at least one transition metal-carbene complex of formula I as claimed in  claim 1 .  
   
   
       10 . An OLED comprising a light-emitting layer as claimed in  claim 9 .  
   
   
       11 . A device selected from the group consisting of stationary visual display units of computers, televisions, visual display units in printers, kitchen appliances and advertising panels, illuminations, and information panels; and mobile visual display units in mobile telephones, laptops, vehicles and destination displays in buses and trains, comprising an OLED as claimed in  claim 8 .  
   
   
       12 . A method of using an uncharged transition metal-carbene complex of formula I as claimed in  claim 1  for the bulk coloration of polymeric materials.  
   
   
       13 . A device selected from the group consisting of stationary visual display units of computers, televisions, visual display units in printers, kitchen appliances and advertising panels, illuminations, and information panels; and mobile visual display units in mobile telephones, laptops, vehicles and destination displays in buses and trains, comprising an OLED as claimed in  claim 10 . 
 Photoluminescence (“Pl”) of the indium-carbene complexes                                                    PL in toluene   PL in polymethacrylate (“PMMA”) film   PL in powder                                                   Complex   λ em * [nm]   QY** [%]   CIE x   CIE y   λ em * [nm]   QY** [%]   CIE x   CIE y   CIE x   CIE y                                                         Ir(pipic) 3     398   1   0.161   0.080   —   —   —   —   0.160   0.059     Ir(cn-pibic) 3     382-454   7   0.151   0.095   454   70   0.150   0.096   —   —     Ir(psmbic) 3     472   <1   0.251   0.270   472   4   0.160   0.199   0.266   0.248     Ir(cl-pmic) 3     407   4   0.164   0.062   393, 460   2   0.180   0.149   0.195   0.212     Ir( t bu-cn-pmic) 3     431-455   26   0.149   0.099   458   55   0.149   0.105   —   —     fac-Ir(cn-pmic) 3     470   8   0.174   0.234   452   73   0.150   0.092   0.277   0.437     Ir(me 2 -cn-pmic) 3     —   —   —   —   464   67   0.149   0.141   0.279   0.382     Ir(cn-pmbic) 3     —   —   —   —   454   78   0.150   0.095   0.220   0.262     Ir(pymic) 3     403   7   0.165   0.073   478   —   0.182   0.271   0.564   0.410     Ir(btmbic) 3     —   —   —   —   493, 527,   —   0.318   0.547   —   —                         557     Ir(pombic) 3     408, 433,   —   0.195   0.138   407, 433,   10   0.156   0.082   0.440   0.441         458               457             *Wavelength(s) λ em  of the emission maximum or of the emission maxima          **Quantum yield.                                                         The PL measurements in toluene were performed with an emitter concentration of 2 mg/l in quartz cuvettes (10×10 mm). The excitation wavelength was 325 nm (HeCd laser) and the emission was detected at an angle of 90 degrees by means of fiber optics in a diode array spectrometer.    The PL measurements in PMMA were performed with an emitter doping of 2%. These were produced as follows: 2 mg/l of emitter were dissolved in a 10% PMMA solution in dichloromethane (Mw 120 kD) and knife-coated onto a microscope slide with a 60 μm doctor blade. The excitation wavelength was 325 nm (HeCd laser); the excitation was at right angles to the microscope slide and the emission was detected at an angle of 45 degrees by means of fiber optics in a diode array spectrometer.    For the OLED described, the following electrooptical data are obtained:                                                    Emission maximum   476   nm                       CIE(x, y)   0.21; 0.30                           Photometric efficiency   10.0   cd/A         Power efficiency   11.6   lm/W                       External quantum yield   5.0%                           Photometric efficiency at an   4.0   cd/A         luminance of 100 cd/m 2           Maximum luminance   3500   cd/m 2                                                                          c)    The ITO substrate is pretreated as described under a).    Subsequently, PEDT:PSS (poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)) (Baytron® P VP Al 4083) is spin-coated from aqueous solution onto the substrate in a thickness of 46 nm and the emitter layer is applied in a thickness of approx. 48 nm from PMMA dissolved in chlorobenzene (16.5 mg of PMMA for 1 ml of chlorobenzene) and the emitter substance 1 c). The concentration of the emitter corresponds to a 30% by weight doping of PMMA. Afterward, a hole blocker and electron conductor layer of BCP in a thickness of 52.5 nm, a 0.75 nm-thick lithium fluoride layer and finally a 110 nm-thick Al electrode are applied by vapor deposition.    To characterize the OLED, electroluminescence spectra are recorded at various currents and voltages. In addition, the current-voltage characteristic is measured in combination with the emitted light output. The light output may be converted to photometric parameters by calibration with a photometer.    For the OLED described, the following electrooptical data are obtained:                                                    Emission maximum   460   nm         Photometric efficiency   4.3   cd/A         Power efficiency   1.1   lm/W                       External quantum yield   3.5%                           Photometric efficiency at an   1.2   cd/A         luminance of 100 cd/m 2           Maximum luminance   150   cd/m 2