Electron injection layer for an organic light-emitting diode (OLED)

Organic light emitting diode comprising at least one emission layer, an electron injection layer and at least one cathode electrode, wherein:

• the electron injection layer comprises an organic phosphine compound, wherein the electron injection layer is free of a metal, metal salt, metal complex and metal organic compound;
• the cathode electrode comprises at least a first cathode electrode layer and at least a second cathode electrode layer, wherein
• the first cathode electrode layer comprises a first zero-valent metal selected from Yb;
• and the composition of the first cathode electrode layer differs from the composition of the second cathode electrode layer, wherein the second cathode electrode layer comprises at least an additional metal, wherein the additional metal is an MgAg alloy;
• and wherein
• the electron injection layer is arranged in direct contact to the first cathode electrode layer;
• the first cathode electrode layer does not comprise or consist of an organic compound;
• the organic light emitting diode is a top emission device;
• and
• the organic phosphine compound of the electron injection layer is a compound having the Formula Ia:
• wherein:
• X is selected from O, S, or Se;
• R1 and R2 are independently selected from C1 to C12 alkyl, substituted or unsubstituted C6 to C20 aryl or substituted or unsubstituted C5 to C20 heteroaryl;
• or R1 and R2 are bridged with an alkene-di-yl group forming with the P atom a substituted or unsubstituted five, six or seven membered ring;
• and
• A1 is phenyl or selected from Formula (II):
• wherein
• R3 is selected from C1 to C8 alkane-di-yl, substituted or unsubstituted C6 to C20 arylene, or substituted or unsubstituted C5 to C20 heteroarylene;
• or
• A1 is selected from Formula (III)
• wherein
• n is selected from 0 or 1;
• m is selected from 1 or 2;
• o is selected from 1 or 2;
• and m is 1 if o is 2;
• Ar1 is selected from substituted or unsubstituted C6 to C20 arylene and substituted or unsubstituted C5 to C20 heteroarylene;
• Ar2 is selected from substituted or unsubstituted C18 to C40 arylene and substituted or unsubstituted C10 to C40 heteroarylene;
• R4 is selected from H, C1 to C12 alkyl, substituted or unsubstituted C6 to C20 aryl and substituted or unsubstituted C5 to C20 heteroaryl.