# US 9,520,532 B2 · Light emitting element and light emitting device using the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,532 B2 - Document ID: US9520532B2 - Status: Granted - Kind: B2 - Application number: 14/521,695 - Filed: 2014-10-23 - Published: 2015-02-05 - Granted: 2016-12-13 - Earliest claimed: 2004-07-23 - Assignees: Semiconductor Energy Laboratory Co., Ltd. - Applicants: Semiconductor Energy Laboratory Co., Ltd. - Inventors: Daisuke Kumaki; Satoshi Seo - Web page: https://patentgrep.com/patent/US9520532B2 ## CPC - H10K 50/155: comprising dopants - H10H 20/80: Constructional details - H10H 20/81: Bodies - H10H 20/833: Transparent materials - H10H 20/856: Reflecting means - H10H 29/10: Integrated devices comprising at least one light-emitting semiconductor component covered by group H10H20/00 (active-matrix LED displays H10H29/30) - H10K 50/157: {between the light-emitting layer and the cathode} - H10K 50/165: comprising dopants - H10K 50/30: Organic light-emitting transistors - H10K 50/852: comprising a resonant cavity structure, e.g. Bragg reflector pair - H10K 59/12: Active-matrix OLED [AMOLED] displays - H10K 85/324: {comprising aluminium, e.g. Alq3} - H10K 2102/351: {Thickness} - H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES - H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS ## 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. ## Claims ### 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, and wherein the first electrode and the second electrode are a cathode and an anode, respectively. ### Claim 2 (depends on 1) The light-emitting device according to claim 1, wherein: the first layer comprises a first substance having a hole transporting property and a second substance having an electron accepting property to the first substance; and the second layer comprises a third substance having the electron transporting property and a fourth substance having an electron donating property to the third substance. ### Claim 3 (depends on 2) The light-emitting device according to claim 2, wherein: the hole transporting property of the first substance is stronger than an electron transporting property thereof; and the electron transporting property of the third substance is stronger than a hole transporting property thereof. ### Claim 4 (depends on 1) The light-emitting device according to claim 1, wherein: the first layer comprises a p-type semiconductor; and the second layer comprises an n-type semiconductor. ### Claim 5 (depends on 4) The light-emitting device according to claim 4, wherein: the first layer further comprises an electron-accepting substance with respect to the p-type semiconductor; and the second layer further comprises an electron-donating substance with respect to the n-type semiconductor. ### Claim 6 (depends on 1) The light-emitting device according to claim 1, wherein the second layer is in direct contact with the third layer. ### Claim 7 (depends on 1) The light-emitting device according to claim 1, wherein the second electrode is configured to transmit light emitted from the third layer. ### Claim 8 A light-emitting device comprising: 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. ### Claim 9 (depends on 8) The light-emitting device according to claim 8, further comprising a driver circuit electrically connected to the external input terminal through the wiring. ### Claim 10 (depends on 9) The light-emitting device according to claim 9, wherein the driver circuit is provided over the substrate. ### Claim 11 (depends on 9) The light-emitting device according to claim 9, wherein the driver circuit is provided outside the substrate. ### Claim 12 (depends on 8) The light-emitting device according to claim 8, further comprising an IC chip over the external input terminal. ### Claim 13 (depends on 8) The light-emitting device according to claim 8, further comprising a printed wiring board connected to the external input terminal. ### Claim 14 (depends on 8) The light-emitting device according to claim 8, wherein: the first layer comprises a first substance having a hole transporting property and a second substance having an electron accepting property to the first substance; and the second layer comprises a third substance having the electron transporting property and a fourth substance having an electron donating property to the third substance. ### Claim 15 (depends on 14) The light-emitting device according to claim 14, wherein: the hole transporting property of the first substance is stronger than an electron transporting property thereof; and the electron transporting property of the third substance is stronger than a hole transporting property thereof. ### Claim 16 (depends on 8) The light-emitting device according to claim 8, wherein: the first layer comprises a p-type semiconductor; and the second layer comprises an n-type semiconductor. ### Claim 17 (depends on 16) The light-emitting device according to claim 16, wherein: the first layer further comprises an electron-accepting substance with respect to the p-type semiconductor; and the second layer further comprises an electron-donating substance with respect to the n-type semiconductor. ### Claim 18 (depends on 8) The light-emitting device according to claim 8, wherein the second electrode is configured to transmit light emitted from the third layer. ### Claim 19 (depends on 8) An electronic appliance comprising the light-emitting device according to claim 8.