Organic electroluminescent device

Claim 2

An organic electroluminescent device character­ized by comprising: first and second electrodes (2 and 3) opposite to each other; and a multi-layered body consisting of a plurality of organic films including a light-emitting layer, said multi-layered body being sandwiched between said elec­trodes (2 and 3), wherein said device satisfies the fol­lowing inequalities: E M1 < E₁ E₂ < E M2 E C1 > E C2 E V1 > E V2 where E M1 is a work function of said first electrode (2); E M2 is a work function of said second electrode (3); E C1 , E₁, and E V1 are energy differences between a vacuum level and a lower end of a conduction band, the vacuum level and a Fermi level, and the vacuum level and an upper end of a valence band of a first organic film (4) on said first electrode (2) side of said multi-­layered body, respectively, and E C2 , E₂, and E V2 are energy differences between a vacuum level and a lower end of a conduction band, the vacuum level and a Fermi level, and the vacuum level and an upper end of a valence band of a second organic film (5) on said second electrode (3) side of said multi-­layered body, respectively.

Claim 3

An organic electroluminescent device according to claim 1, characterized in that said multi-layered body includes said first organic film (4) in contact with said first electrode (2) said second organic film (5) in contact with said second electrode (3) and a third organic film (6) with a band gap smaller than those of said first and second organic films, said third organic film being sandwiched between said first and second organic films (4 and 5) and serving as a light-­emitting layer.

Claim 4

An organic electroluminescent device according to claim 2, characterized in that the following inequalities are satisfied: E C3 > E C2 E V1 > E V3 where E C3 and E V3 are energy differences between a vac­uum level and a lower end of a conduction band, and the vacuum level and an upper end of a valence band of said third organic film (6), respectively.

Claim 5

An organic electroluminescent device according to claim 3, characterized in that the following inequalities are satisfied: E M1 < E3 < E M2 E C1 ≦ E C3 E V3 ≦ E V2 where E₃ is an energy difference between the vacuum level and the Fermi level of said third organic film (6).

Claim 6

An organic electroluminescent device according to claim 3, characterized in that the following inequalities are satisfied: E₃ < E M2 E C1 > E C3 E V3 ≦ E V2 where E₃ is an energy difference between the vacuum level and the Fermi level of said third organic film (6).

Claim 7

An organic electroluminescent device according to claim 3, characterized in that the following inequalities are satisfied: E M1 < E₃ E C1 ≦ E C3 E V3 > E V2 where E₃ is an energy difference between the vacuum level and the Fermi level of said third organic film (6).

Claim 8

An organic electroluminescent device according to claim 1, characterized in that said multi-layered body includes: said first organic film (4) in contact with said first electrode (2); said second organic film (5) in contact with said second electrode (3); and said third organic film (6) in contact with said first organic film (4) and a fourth organic film (7) in contact with said second organic film (5), said third and fourth organic films each having a band gap smaller than those of said first and second organic films being sandwiched between said first and second organic films (4 and 5), and serving as light-emitting layers.

Claim 9

An organic electroluminescent device according to claim 7, characterized in that the following inequalities are satisfied: E M1 < E₃ E₄ < E M2 E C1 ∼ E C3 ∼ E C4 > E C2 E V2 ∼ E V4 < E V3 ∼ E V1 where E C3 and E V3 are energy differences between a vac­uum level and a lower end of a conduction band, and the vacuum level and an upper end of a valence band of said third organic film (6), respectively; and E C4 and E V4 are energy differences between a vacuum level and a lower end of a conduction band, and the vac­uum level and an upper end of a valence band of said fourth organic film (7).

Claim 10

An organic electroluminescent device according to claim 1, characterized in that said multi-layered body includes: said first organic film (4), serving as a first light-emitting layer, in contact with said first electrode (2); and said second organic film (5), serving as a second light-emitting layer, in contact with said second elec­trode (3), electrons injected from said first electrode (2) into said first organic film (4) and holes injected from said second electrode (3) into said second organic film (5) are accumulated at a blocking barrier junction between said first and second organic films (4 and 5) when a biasing voltage is applied between said first and second electrodes (2 and 3) to set said second electrode (3) at a positive potential, and of the accumulated electrons and holes, the elec­trons are tunnel-injected into said second organic film (5) at a first threshold voltage to perform radiative recombination in said second organic film (5), and the holes are tunnel-injected into said first organic film (4) at a second threshold voltage different from the first threshold voltage to perform radiative recombi­nation in said first organic film (4).

Claim 11

An organic electroluminescent device according to claim 9, characterized in that said first and second organic films (4 and 5) have the following relationship, and hence the first threshold voltage is set to be smaller than the second threshold voltage: E C1 - E C2 < E V1 - E V2

Claim 12

An organic electroluminescent device according to claim 9, characterized in that said first and second organic films (4 and 5) have the following relationship, and hence the first threshold voltage is set to be larger than the second threshold voltage: E C1 - E C2 > E V1 - E V2

Claim 13

An organic electroluminescent device according to claim 1, characterized in that said multi-layered body includes: said first organic film (4) in contact with said first electrode (2); said second organic film (5), serving as a first light-emitting layer, in contact with said first organic film (4), and said third organic film (6), serving as a second light-emitting layer, sandwiched between said second organic film (5) and said second electrode (3), electrons injected from said first electrode (2) into said first organic film (4) and holes injected from said second electrode (3) into said second organic film (5) through said third organic film (6) are accumulated at a blocking barrier junction between said first and second organic films (4 and 5) when a biasing voltage is applied between said first and second electrodes (2 and 3; to set said second electrode (3) at a positive potential, and of the accumulated electrons and holes, the elec­trons are tunnel-injected into said second organic film (5) at a first threshold voltage to perform radiative recombination in said second organic film (5), and are transported to said third organic film (6) at a second threshold voltage to perform radiative recombination in said third organic film (6).

Claim 14

An organic electroluminescent device according to claim 12, characterized in that the following inequalities are satisfied: E C1 - E C2 < E V1 - E V2 E C2 < E C3 E V2 ∼ E V3 E M2 > E₃ where E C3 , E₃, and E V3 are energy differences between a vacuum level and a lower end of a conduction band, the vacuum level and a Fermi level, and the vacuum level and an upper end of a valence band of said third organic film, respectively.

Claim 15

An organic electroluminescent device according to claim 1, characterized in that said multi-layered body includes: said first organic film (4) serving as a first light-emitting layer; said second organic film (5) sandwiched between said first organic film (4) and said second electrode (3); and said third organic film (6), serving as a second light-emitting layer, sandwiched between said first organic film (4) and said first electrode (2), and electrons injected from said first electrode (2) into said first organic film (4) through said third organic film (6) and holes injected from said second electrode (3) into said second organic film (5) are accumulated at a blocking barrier junction between said first and second organic films (4 and 5) when a biasing voltage is applied between said first and second elec­trodes (2 and 3) to set said second electrode (3) at a positive potential, and of the accumulated electrons and holes, the holes are tunnel-injected into said first organic film (4) at a first threshold voltage to perform radiative recombi­nation in said first organic film (4), and are trans­ported to said third organic film (6) at a second threshold voltage to perform radiative recombination in said third organic film (6).

Claim 16

An organic electroluminescent device according to claim 14, characterized in that the following inequalities are satisfied: E C1 - E C2 < E V1 - E V2 E C3 ∼ E C1 E V3 < E V1 E M1 < E₃ where E C3 , E₃, and E V3 are energy differences between a vacuum level and a lower end of a conduction band, the vacuum level and a Fermi level, and the vacuum level and an upper end of a valence band of said third organic film (6), respectively.

Claim 17

An organic electroluminescent device including a multi-layered body consisting of first and second organic films (4 and 5), at least one of said first and second organic films serving a light-emitting layer, and a junction between said first and second organic films having a blocking barrier which blocks the flow of elec­trons from said first organic film (4) into said second organic film (5), and a blocking barrier which blocks the flow of holes from said second organic film (5) into said first organic film (4), a first electrode (2) for electron injection formed to be in contact with said first organic film (4); and a second electrode (3) for hole injection formed to be in contact with said second organic film (5), wherein electrons injected from said first electrode (2) into said first organic film (4) and holes injected from said second electrode (3) into said second organic film (5) are accumulated at said junction to form an electric double layer when a biasing voltage is applied between said first and second electrodes (2 and 3) to set said second electrode (3) at a positive potential, and at least one type of electrons and holes which constitute said electric double layer tunnel a blocking barrier formed in said junction at a predetermined threshold voltage to recombine with the other type, thus achieving light emission.

Claim 18

An organic electroluminescent device including a multi-layered body consisting of first and second organic films (4 and 5), at least one of said first and second organic films serving a light-emitting layer, and a junction between said first and second organic films having a blocking barrier which blocks the flow of elec­trons from said first organic film (4) into said second organic film (5), and a blocking barrier which blocks the flow of holes from said second organic film (5) into said first organic film (4), a first electrode (2) for electron injection formed to be in contact with said first organic film (4); and a second electrode (3) for hole injection formed to be in contact with said second organic film (5), wherein electrons injected from said first electrode (2) into said first organic film (4) and holes injected from said second electrode (3) into said second organic film (5) are accumulated at said junction to form an electric double layer when a biasing voltage is applied between said first and second electrodes (2 and 3) to set said second electrode (3) at a positive potential, and at least one type of electrons and holes which constitute said electric double layer tunnel a blocking barrier formed in said junction at a predetermined threshold voltage to recombine with the other type, thus achieving light emission.