Light emitting element and light emitting device using the same
First Claim
1. A light-emitting device comprising:
- a transistor over a substrate;
a first electrode over and electrically connected to the transistor;
a first layer over and in direct contact with the first electrode, the first layer being configured to generate a hole;
a second layer over and in direct contact with the first layer, the second layer being configured to generate an electron;
a third layer over the second layer, the third layer being configured to emit light; and
a second electrode over the third layer,wherein the first layer is a single layer,wherein the second layer is a single layer,wherein an electron transporting property of the second layer is stronger than a hole transporting property of the second layer, andwherein the first electrode and the second electrode are a cathode and an anode, respectively.
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Abstract
An object of the present invention is to provide a light emitting element having slight increase in driving voltage with accumulation of light emitting time. Another object of the invention is to provide a light emitting element having slight increase in resistance value with increase in film thickness. A light emitting element of the invention includes a first layer for generating holes, a second layer for generating electrons and a third layer comprising a light emitting substance between first and second electrodes. The first and third layers are in contact with the first and second electrodes, respectively. The second and third layers are connected to each other so as to inject electrons generated in the second layer into the third layer when applying the voltage to the light emitting element such that a potential of the second electrode is higher than that of the first electrode.
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Citations
19 Claims
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1. A light-emitting device comprising:
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a transistor over a substrate; a first electrode over and electrically connected to the transistor; a first layer over and in direct contact with the first electrode, the first layer being configured to generate a hole; a second layer over and in direct contact with the first layer, the second layer being configured to generate an electron; a third layer over the second layer, the third layer being configured to emit light; and a second electrode over the third layer, wherein the first layer is a single layer, wherein the second layer is a single layer, wherein an electron transporting property of the second layer is stronger than a hole transporting property of the second layer, and wherein the first electrode and the second electrode are a cathode and an anode, respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A light-emitting device comprising:
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a substrate; a pixel portion over the substrate; a wiring over the substrate, the wiring electrically connected to the pixel portion; and an external input terminal electrically connected to the wiring, wherein; the pixel portion comprises a plurality of pixels arranged in a matrix form; and at least one of the pixels comprises; a transistor; a first electrode over and electrically connected to the transistor; a first layer over and in direct contact with the first electrode, the first layer being configured to generate a hole; a second layer over and in direct contact with the first layer, the second layer being configured to generate an electron; a third layer over the second layer, the third layer being configured to emit light; and a second electrode over the third layer, wherein the first layer is a single layer, wherein the second layer is a single layer, wherein an electron transporting property of the second layer is stronger than a hole transporting property of the second layer; and wherein the first electrode and the second electrode are a cathode and an anode, respectively. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification