Patent EP-1848049-A1 (EP)
Title: Light emitting device
Inventor: BIRNSTOCK JAN
IPC: H01L51/50
Filed: 2006-05-05
Abstract: The light emitting diode comprises an arrangement of layers on a substrate (1) comprising an anode (2)- and a cathode contact, which are electrically contacted with a light emitting layer pile arranged between the anode- and the cathode contact, which on its part comprises of a polymer layer (4) and a low-molecular layer out of small molecules of an organic material separable by means of a vacuum evaporation. The small molecules are built as donor molecules with an oxidation potential in comparison to Fc/Fc +> (ferrocene/ferrocenium redox pair) of a maximum of -2.2 V. The light emitting diode comprises an arrangement of layers on a substrate (1) comprising an anode (2)- and a cathode contact, which are electrically contacted with a light emitting layer pile arranged between the anode- and the cathode contact, which on its part comprises of a polymer layer (4) and a low-molecular layer out of small molecules of an organic material separable by means of a vacuum evaporation. The small molecules are built as donor molecules with an oxidation potential in comparison to Fc/Fc +> (ferrocene/ferrocenium redox pair) of a maximum of -2.2 V, if the low-molecular layer is arranged adjacent to the cathode contact, and as acceptor molecules with a reduction potential in comparison to the Fc/Fc +> of -0.24 V, if the low-molecular layer is arranged adjacent to the anode contact. The light emitting layer pile comprises a further low-molecular layer made out of small molecules of a further organic material separable by means of vacuum evaporation. The small molecules of the further low-molecular layer is built as acceptor molecules with an oxidation potential of maximum of -0.24 V, in comparison to Fc/Fc +>, if the further low-molecular layer is arranged adjacent to the anode contact and the low-molecular layer is arranged adjacent to the cathode contact, and as donor molecules with a reduction potential in comparison to Fc/Fc +> of -2.2 V, if the further low-molecular layer is arranged adjacent to the anode contact and the low-molecular layer is arranged adjacent to the cathode contact. The donor molecules and/or the acceptor molecules have a molar mass of 200-1000g/mol. The low-molecular and/or the further low-molecular layer have a layer thickness 1-5 nm. The polymer layer is a light emitting and a charge carrier transporting layer and has a layer thickness of 50-100 nm. Between the anode contact and the polymer layer a polymer hole injection layer (3) with a thickness of 50-100 nm is arranged, if the low-molecular layer is arranged adjacent to the cathode contact. Between the low-molecular layer and the polymer layer a low-molecular organic electron transport layer (6) with a thickness of 20-100 nm is arranged, if the low-molecular layer is arranged adjacent to the cathode contact. The low-molecular organic electron transport layer comprises an organic matrix material, which is electrically doped with a low-molecular organic donor material and consists of a doping concentration (donor material molecules: matrix material molecule) of 1:100-1:10. The organic donor material has a molar mass of 200-1000g/mol. Between the low-molecular layer and the polymer layer a low-molecular organic block layer with a thickness of 5-20 nm is arranged, if the low-molecular layer is arranged adjacent to the cathode contact. Between the cathode contact and the polymer layer a polymer electron injection layer with a thickness of 50-100 nm is arranged, if the low-molecular layer is arranged adjacent to the anode contact. Between the low-molecular layer and the polymer layer a low-molecular organic hole transporting layer with a thickness of 20-100 nm is arranged, if the low-molecular layer is arranged adjacent to the anode contact. The low-molecular organic hole transport layer comprises an organic matrix material, which is electronically doped with a low-molecular organic acceptor material and has a doping concentration (acceptor molecule: matrix-material molecule) of 1:100-1:10. The organic acceptor material has a molecular mass of 200-1000g/mol. Between the low-molecular layer and the polymer layer a further low-molecular organic block layer with a thickness of 5-20 nm is arranged, if the low-molecular layer is arranged adjacent to the anode contact. The arrangement of layers is constructed as inverted design, non-inverted design, light that is generated in the light emitting layer pile, design that emits away from the substrate (top-emission) and light that is generated in the light emitting layer pile, through a substrate emitting design (bottom-emission). The arrangement of layers is transparent with the substrate. A base contact and a cover contact are intended, which are built by means of the anode contact or the cathode contact.