# US 10,504,423 B2 · Display device and electronic device including display device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,504,423 B2 - Document ID: US10504423B2 - Status: Granted - Kind: B2 - Application number: 16/130,447 - Filed: 2018-09-13 - Published: 2019-01-10 - Granted: 2019-12-10 - Earliest claimed: 2009-10-21 - Assignees: Semiconductor Energy Laboratory Co., Ltd. - Applicants: Semiconductor Energy Laboratory Co., Ltd. - Inventors: Shunpei Yamazaki; Jun Koyama; Hiroyuki Miyake - Web page: https://patentgrep.com/patent/US10504423B2 ## CPC - G09G 3/3208: organic, e.g. using organic light-emitting diodes [OLED] - G09G 3/2003: {Display of colours (specific for liquid crystal displays G09G3/3607)} - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - H01L 27/1225 - H01L 27/3262 - H01L 27/3276 - H01L 29/7869 - H01L 29/78609 - H01L 29/78693 - H01L 29/78696 - G09G 2330/021: Power management, e.g. power saving - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) - H01L ## Abstract Objects are to provide a display device the power consumption of which is reduced, to provide a self-luminous display device the power consumption of which is reduced and which is capable of long-term use in a dark place. A circuit is formed using a thin film transistor in which a highly-purified oxide semiconductor is used and a pixel can keep a certain state (a state in which a video signal has been written). As a result, even in the case of displaying a still image, stable operation is easily performed. In addition, an operation interval of a driver circuit can be extended, which results in a reduction in power consumption of a display device. Moreover, a light-storing material is used in a pixel portion of a self-luminous display device to store light, whereby the display device can be used in a dark place for a long time. ## Claims ### Claim 1 A display device comprising: a driving transistor comprising: a first gate electrode; a second gate electrode over the first gate electrode; a first oxide semiconductor layer between the first gate electrode and the second gate electrode; a first source electrode over and electrically connected to the first oxide semiconductor layer; and a first drain electrode over and electrically connected to the first oxide semiconductor layer; a switching transistor comprising: a second oxide semiconductor layer; a third gate electrode over the second oxide semiconductor layer; a second source electrode over and electrically connected to the second oxide semiconductor layer; and a second drain electrode over and electrically connected to the second oxide semiconductor layer; and an organic EL element, wherein the switching transistor does not comprise a gate electrode under the second oxide semiconductor layer, wherein the organic EL element comprises a first electrode, a second electrode over the first electrode, and a layer comprising an organic compound between the first electrode and the second electrode, wherein one of the second source electrode and the second drain electrode is electrically connected to a signal line, wherein the other of the second source electrode and the second drain electrode is electrically connected to one of the first gate electrode and the second gate electrode of the driving transistor, wherein one of the first source electrode and the first drain electrode is electrically connected to the organic EL element, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises indium, gallium, and zinc, wherein a length of the first gate electrode in a channel length direction is larger than a length of the second gate electrode in the channel length direction, and wherein each of the first source electrode and the first drain electrode overlaps with the first gate electrode. ### Claim 2 (depends on 1) The display device according to claim 1, further comprising a color filter under the first electrode of the organic EL element. ### Claim 3 (depends on 1) The display device according to claim 1, wherein the organic EL element is configured to emit white light. ### Claim 4 (depends on 1) The display device according to claim 1, wherein a potential of the first gate electrode is different from a potential of the second gate electrode. ### Claim 5 (depends on 1) The display device according to claim 1, wherein an off-state current of the switching transistor per a channel width of 1 μm is less than or equal to 1×10−16 A/μm. ### Claim 6 (depends on 1) The display device according to claim 1, wherein the first oxide semiconductor layer and the second oxide semiconductor layer each have a hydrogen concentration of less than or equal to 5×1019 /cm3. ### Claim 7 (depends on 1) The display device according to claim 1, wherein each of a carrier concentration of the first oxide semiconductor layer and a carrier concentration of the second oxide semiconductor layer is less than 1×1014 /cm3. ### Claim 8 (depends on 1) An electronic device comprising the display device according to claim 1, wherein the electronic device is any of a portable game machine, a digital camera, a television receiver, a computer, a mobile phone, and an e-book reader. ### Claim 9 A display device comprising: a driving transistor comprising: a first gate electrode; a second gate electrode over the first gate electrode; a first oxide semiconductor layer between the first gate electrode and the second gate electrode; a first source electrode over and electrically connected to the first oxide semiconductor layer; and a first drain electrode over and electrically connected to the first oxide semiconductor layer; a switching transistor comprising: a second oxide semiconductor layer; a third gate electrode over the second oxide semiconductor layer; a second source electrode over and electrically connected to the second oxide semiconductor layer; and a second drain electrode over and electrically connected to the second oxide semiconductor layer; and an organic EL element, wherein the switching transistor does not comprise a gate electrode under the second oxide semiconductor layer, wherein the organic EL element comprises a first electrode, a second electrode over the first electrode, and a layer comprising an organic compound between the first electrode and the second electrode, wherein one of the second source electrode and the second drain electrode is electrically connected to a signal line, wherein the other of the second source electrode and the second drain electrode is electrically connected to one of the first gate electrode and the second gate electrode of the driving transistor, wherein one of the first source electrode and the first drain electrode is electrically connected to the organic EL element, wherein the organic EL element is provided over the driving transistor, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises indium, gallium, and zinc, wherein a length of the first gate electrode in a channel length direction is larger than a length of the second gate electrode in the channel length direction, and wherein each of the first source electrode and the first drain electrode overlaps with the first gate electrode. ### Claim 10 (depends on 9) The display device according to claim 9, further comprising a color filter under the first electrode of the organic EL element. ### Claim 11 (depends on 9) The display device according to claim 9, wherein the organic EL element is configured to emit white light. ### Claim 12 (depends on 9) The display device according to claim 9, wherein a potential of the first gate electrode is different from a potential of the second gate electrode. ### Claim 13 (depends on 9) The display device according to claim 9, wherein an off-state current of the switching transistor per a channel width of 1 μm is less than or equal to 1×10−16 A/μm. ### Claim 14 (depends on 9) The display device according to claim 9, wherein the first oxide semiconductor layer and the second oxide semiconductor layer each have a hydrogen concentration of less than or equal to 5×1019 /cm3. ### Claim 15 (depends on 9) The display device according to claim 9, wherein each of a carrier concentration of the first oxide semiconductor layer and a carrier concentration of the second oxide semiconductor layer is less than 1×1014 /cm3. ### Claim 16 (depends on 9) An electronic device comprising the display device according to claim 9, wherein the electronic device is any of a portable game machine, a digital camera, a television receiver, a computer, a mobile phone, and an e-book reader. ### Claim 17 A display device comprising: a driving transistor comprising: a first gate electrode; a second gate electrode over the first gate electrode; a first oxide semiconductor layer between the first gate electrode and the second gate electrode; and a first electrode over and electrically connected to the first oxide semiconductor layer; and a switching transistor comprising: a second oxide semiconductor layer; and a third gate electrode over the second oxide semiconductor layer; an organic EL element, wherein the switching transistor does not comprise a gate electrode under the second oxide semiconductor layer, wherein the organic EL element comprises a second electrode, a third electrode over the second electrode, and a layer comprising an organic compound between the second electrode and the third electrode, wherein the switching transistor is electrically connected to a signal line, wherein one of a source and a drain of the switching transistor is electrically connected to one of the first gate electrode and the second gate electrode of the driving transistor, wherein one of a source and a drain of the driving transistor is electrically connected to the organic EL element, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises indium, gallium, and zinc, wherein a length of the first gate electrode in a channel length direction is larger than a length of the second gate electrode in the channel length direction, and wherein the first electrode overlaps with the first gate electrode. ### Claim 18 (depends on 17) The display device according to claim 17, further comprising a color filter under the first electrode of the organic EL element. ### Claim 19 (depends on 17) The display device according to claim 17, wherein the organic EL element is configured to emit white light. ### Claim 20 (depends on 17) The display device according to claim 17, wherein a potential of the first gate electrode is different from a potential of the second gate electrode. ### Claim 21 (depends on 17) The display device according to claim 17, wherein an off-state current of the switching transistor per a channel width of 1 μm is less than or equal to 1×10−16 A/μm. ### Claim 22 (depends on 17) The display device according to claim 17, wherein the first oxide semiconductor layer and the second oxide semiconductor layer each have a hydrogen concentration of less than or equal to 5×1019 /cm3. ### Claim 23 (depends on 17) The display device according to claim 17, wherein each of a carrier concentration of the first oxide semiconductor layer and a carrier concentration of the second oxide semiconductor layer is less than 1×1014 /cm3. ### Claim 24 (depends on 17) An electronic device comprising the display device according to claim 17, wherein the electronic device is any of a portable game machine, a digital camera, a television receiver, a computer, a mobile phone, and an e-book reader.