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EP-4250897-B1 - ORGANIC LIGHT EMITTING DIODE DISPLAY

EP4250897B1EP 4250897 B1EP4250897 B1EP 4250897B1EP-4250897-B1

Inventors

  • KIM, SE-HO
  • PARK, JIN-WOO
  • Lee, Won-Se

Dates

Publication Date
20260513
Application Date
20130802

Claims (15)

  1. An organic light emitting diode display comprising: a substrate (110); a first voltage line (172); a plurality of driving circuits on the substrate (110); a plurality of organic light emitting diodes (OLED), each of the organic light emitting diodes (OLED) being electrically coupled to a respective driving circuit; wherein each of the driving circuits comprises: a first, switching, thin film transistor (T2) implemented in a first portion (131b) of a semiconductor layer (131) and coupled to a first scan line (121) and a data line (171); a second, driving, thin film transistor (T1) implemented in a second portion (131a) of the semiconductor layer (131) and electrically coupled to the first voltage line (172) and one of the organic light emitting diodes (OLED), the semiconductor layer (131) electrically coupling the second thin film transistor (T1) to the first thin film transistor (T2), the second portion (131a) of the semiconductor layer (131) having a bent portion in a channel region of the second thin film transistor (T1); a gate insulating layer (141) covering the second portion (131a) of the semiconductor layer (131); a storage capacitor (Cst) electrically coupled to a gate electrode of the second thin film transistor (T1), the storage capacitor (Cst) comprising: a first capacitor plate (125a, 125h, Cst1) comprising the gate electrode of the second thin film transistor (T1); a second capacitor plate (127, Cst2) overlapping the first capacitor plate (125a, 125h, Cst1); and an insulating layer (142), between the first capacitor plate (125a, 125h, Cst1) and the second capacitor plate (127, Cst2), the insulating layer (142) covering the second thin film transistor (T1); and a third, compensation, thin film transistor (T3) implemented in a third portion (131c) of the semiconductor layer (131) and electrically coupled to the one of the organic light emitting diodes (OLED) and the first capacitor plate (125a, 125h, Cst1), the semiconductor layer (131) electrically coupling the third thin film transistor (T3) to the second thin film transistor (T1), wherein the bent portion of the second portion of the semiconductor layer (131) is under the gate electrode of the second thin film transistor (T1) and is covered by the first capacitor plate (125a, 125h, Cst1).
  2. The organic light emitting diode display according to claim 1, further comprising a fourth, operation control, thin film transistor (T5) implemented in a fourth portion (131e) of the semiconductor layer (131) and electrically coupled to the first voltage line (172), wherein the semiconductor layer (131) electrically couples the fourth thin film transistor (T5) to the second thin film transistor (T1).
  3. The organic light emitting diode display according to claim 2, further comprising a fifth, light emission control, thin film transistor (T6) implemented in a fifth portion (131f) of the semiconductor layer (131) and electrically coupled to the one of the organic light emitting diodes (OLED), wherein the semiconductor layer (131) electrically couples the fifth thin film transistor (T6) to the second thin film transistor (T1).
  4. The organic light emitting diode display according to claim 3, wherein gate electrodes (G5, G6) of the fourth (T5) and fifth thin film transistors (T6) are coupled together and are configured to receive a signal from a light emission control line (123).
  5. The organic light emitting diode display according to claim 3 or 4, further comprising a protective layer (180) covering the plurality of driving circuits, wherein each of the organic light emitting diodes (OLED) further comprises a pixel electrode (191) on the protective layer (180), the pixel electrode (191) being electrically coupled to a drain electrode of the fifth thin film transistor (T6) through a contact hole (181, 163).
  6. The organic light emitting diode display according to any one of claims 3 to 5, further comprising: a second voltage line (Vint); and a sixth, initialization, thin film transistor (T4) implemented in a sixth portion (131d) of the semiconductor layer (131) and electrically coupled to the second voltage line (Vint) and the first capacitor plate (125a, 125h, Cst1), wherein the semiconductor layer (131) electrically couples the sixth thin film transistor (T4) to the third thin film transistor (T3).
  7. The organic light emitting diode display according to claim 6, further comprising a seventh, current control, thin film transistor (T7) implemented in a seventh portion (131g) of the semiconductor layer (131) and electrically coupled to the second voltage line (Vint) and the one of the organic light emitting diodes (OLED), wherein the semiconductor layer (131) electrically couples the seventh thin film transistor (T7) to the fifth thin film transistor (T6), preferably wherein a gate electrode (G7) of the seventh thin film transistor (T7) is configured to receive a signal from a bypass control line (BP).
  8. The organic light emitting diode display according to claim 6 or 7, wherein the gate electrode (G4) of the sixth thin film transistor (T4) is configured to receive a signal from a second scan line (121).
  9. The organic light emitting diode display according to any preceding claim, wherein gate electrodes (G2, G3) of the first (T2) and third thin film transistors (T3) are coupled together and are configured to receive a signal from the first scan line (121).
  10. The organic light emitting diode display according to any preceding claim, wherein: the second capacitor plate (127, Cst2) is electrically coupled to the first voltage line (172); and/or a periphery of the second capacitor plate (127, Cst2) completely surrounds a periphery of the first capacitor plate (125a, 125h, Cst1) in a plan view.
  11. The organic light emitting diode display according to any preceding claim, wherein either: portions of the semiconductor layer (131) are doped with N-type impurities; or. portions of the semiconductor layer (131) are doped with P-type impurities, wherein each doped portion is a source region or a drain region at a side of a channel region of a thin film transistor.
  12. The organic light emitting diode display according to any preceding claim, further comprising a protective layer (180) covering the plurality of driving circuits, wherein each of the organic light emitting diodes (OLED) further comprises a pixel electrode (191) on the protective layer (180), the pixel electrode (191) being electrically coupled to the second thin film transistor (T1).
  13. The organic light emitting diode display according to any preceding claim, wherein the first capacitor plate (125a, 125h, Cst1) and the first scan line (121) are in the same material layer.
  14. The organic light emitting diode display according to any preceding claim, wherein any one of: the second portion (131a), including the bent portion (33), of the semiconductor layer (131) has a "S"-shape; the second portion (131a), including the bent portion (33), of the semiconductor layer (131) has a "M"-shape; the second portion (131a), including the bent portion (33), of the semiconductor layer (131) has a "W'-shape.
  15. The organic light emitting diode display according to any preceding claim, wherein: the third thin film transistor (T3) is electrically coupled to the gate electrode (G1) and a drain electrode (D1) of the second thin film transistor (T1); and/or the third thin film transistor (T3) has a dual gate electrode structure.

Description

BACKGROUND 1. Field The described technology relates generally to an organic light emitting diode display. 2. Description of Related Art An organic light emitting diode display includes two electrodes and an organic emission layer interposed therebetween, electrons injected from one electrode and holes injected from the other electrode are combined with each other in the organic emission layer to form an exciton, and light is emitted while the exciton discharges energy. The organic light emitting diode display includes a plurality of pixels, each including an organic light emitting diode that is a self-light emitting element, and a plurality of thin film transistors and capacitors for driving the organic light emitting diode. The plurality of thin film transistors includes a switching thin film transistor and a driving thin film transistor. Such an organic light emitting diode display is e.g. disclosed in JP2011114346, CN1761986 and CN102386209. In the switching thin film transistor, a thin gate insulating layer is formed between a gate electrode and a semiconductor layer to enable rapid switching operation. Because the thickness of the gate insulating layer of the driving thin film transistor, which is formed on the same layer as the switching thin film transistor, is reduced, a driving range of a gate voltage applied to the gate electrode of the driving thin film transistor becomes narrow. Therefore, it may be difficult to control the magnitude of the gate voltage Vgs of the driving thin film transistor to ensure a large number of gray levels. The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology, and may therefore contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. SUMMARY According to the present invention there is provided an organic light emitting diode display. Preferred embodiments are defined in the dependent claims. Merely for completeness, it is noted that each of the drawings references provided in the claims is merely for example and does not limit the subject-matter defined by the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an equivalent circuit of one pixel of an organic light emitting diode display according to a first example embodiment of the present invention.FIG. 2 is a view schematically showing positions of a plurality of thin film transistors and capacitors of the organic light emitting diode display according to the first example embodiment.FIG. 3 is a layout view of one pixel of the organic light emitting diode display according to the first example embodiment.FIG. 4 is a cross-sectional view of the organic light emitting diode display of the first example embodiment shown in FIG. 3, which is taken along the line IV-IV.FIG. 5 is a cross-sectional view of the organic light emitting diode display of the first exemplary embodiment shown in FIG. 3, which is taken along the line V-V.FIG. 5A is an alternative cross-sectional view of the organic light emitting diode display of the first exemplary embodiment shown in FIG. 3, which is taken along the line V-V. Therefore, each reference herein to Fig. 5 may be understood to be a reference to Fig 5 and/or Fig. 5A.FIG. 6 is an enlarged layout view of a driving thin film transistor of an organic light emitting diode display according to a second example embodiment of the present invention.FIG. 7 is a layout view of an organic light emitting diode display according to a third example embodiment of the present invention.FIG. 8 is an enlarged layout view of a driving thin film transistor of an organic light emitting diode display according to a fourth example embodiment of the present invention.FIG. 9 is an enlarged layout view of a driving thin film transistor of an organic light emitting diode display according to a fifth example embodiment of the present invention.FIG. 10 is an equivalent circuit of one pixel of an organic light emitting diode display according to a sixth example embodiment of the present invention.FIG. 11 is a layout view of the organic light emitting diode display according to the sixth example embodiment. DETAILED DESCRIPTION The described technology provides an organic light emitting diode display broadening a driving range of a driving thin film transistor to display a relatively large number of gray levels. The present invention concerns an organic light emitting diode display comprising:a substrate; a first voltage line; a plurality of driving circuits on the substrate (110); a plurality of organic light emitting diodes (OLED), each of the organic light emitting diodes being electrically coupled to a respective driving circuit; wherein each of the driving circuits comprises: a first, switching, thin film transistor implemented in a first portion of a semiconductor layer and coupled to a first scan line and a data line; a second, driving, thin f