Thin film transistor, and pixel and organic light emitting display device having the same

• US 9,236,484 B2
• Filed: 11/04/2011
• Issued: 01/12/2016
• Est. Priority Date: 06/28/2011
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Kim, Chang-Yeop, Kwak, Won-Kyu, Jeong, Jin-Tae
• Primary Examiner(s): Moorad, Waseem
• Assistant Examiner(s): Shah, Sujit
• Application Number:
  US13/289,164
• Publication Number:
  US 20130002616A1
• Time in Patent Office: 1,530 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 29/78615 with a body contact

Abstract

A thin film transistor, a pixel, and an organic light emitting diode (OLED) display including the same are disclosed. The thin film transistor includes a connection to the channel region separate from connections to the source and drain.

Claims

1. A pixel comprising:

an organic light emitting diode (OLED);

a driving transistor including;

a source electrode and a drain electrode respectively connected to a source region and a drain region,

a gate electrode connected to a gate metal layer formed separately from the semiconductor layer, and

a bias electrode connected to a portion of a channel region of the semiconductor layer, wherein the driving transistor is configured to transmit a driving current according to a data signal to the organic light emitting diode (OLED);

a switching transistor transmitting a data signal to the source electrode of the driving transistor corresponding to a first scan signal;

an initialization transistor configured to apply an initialization voltage to the gate electrode of the driving transistor according to a second scan signal during an initialization period;

an assistance transistor configured to apply an assistance voltage to the bias electrode of the driving transistor according to the second scan signal during the initialization period; and

a storage capacitor including a first electrode connected to the gate electrode of the driving transistor and a second electrode connected to a first power source voltage.

2. The pixel of claim 1, wherein a voltage difference between the gate electrode voltage and the source electrode voltage of the driving transistor during the initialization period is a voltage operating the driving transistor.

3. The pixel of claim 1, wherein the second scan signal is a scan signal transmitted to a scan line previous to the scan line transmitted with the first scan signal.

4. The pixel of claim 1, wherein the second scan signal is applied with a gate-on voltage level during the initialization period.

5. The pixel of claim 1, further comprising a threshold voltage compensation transistor configured to operate according to the first scan signal after the initialization period to diode-connect the gate electrode and the drain electrode of the driving transistor and to compensate for a threshold voltage of the driving transistor.

6. The pixel of claim 1, further comprising at least one light emission control transistor between a supply source of the first power source voltage and the organic light emitting diode (OLED) and including a gate electrode configured to receive a light emission control signal to control the light emission of the organic light emitting diode (OLED).

7. The pixel of claim 6, wherein the light emission control signal is transmitted with a gate-on voltage level after the first scan signal and the second scan signal are each transmitted to the pixel with the gate-on voltage level, and are then transmitted with a gate-off voltage level.

8. The pixel of claim 1, wherein the channel region of the driving transistor includes a first connection extended in a first direction, and the bias electrode is connected to the first connection.

9. The pixel of claim 8, wherein the channel region further includes at least one second connection extended in a second direction and at least one additional bias electrode is connected to the second connection.

10. The pixel of claim 9, wherein at least one additional bias electrode applies the same voltage as the assistance voltage to the second connection.

11. The pixel of claim 8, wherein:

the first connection includes an electrode connection connected to the bias electrode and an extension connecting the electrode connection and the channel region, and

the width of the electrode connection is equal to or less than the width of the extension.

12. An organic light emitting diode (OLED) display comprising:

a display unit including a plurality of pixels connected to a plurality of scan lines transmitting a plurality of scan signals, a plurality of data lines transmitting a plurality of data signals, and a plurality of light emission control lines transmitting a plurality of light emission control signals;

a scan driver transmitting a plurality of scan signals;

a data driver transmitting a plurality of data signals, and a light emission driver transmitting a plurality of light emission control signals,

wherein the plurality of pixels respectively comprise;

an organic light emitting diode (OLED);

a driving transistor including

a source electrode and a drain electrode respectively connected to a source region and a drain region,

a gate electrode connected to a gate metal layer formed separately from the semiconductor layer, and

a bias electrode connected to a portion of a channel region of the semiconductor layer,

wherein the driving transistor is configured to transmit a driving current according to a data signal to the organic light emitting diode (OLED);

a switching transistor configured to transmit a data signal to the source electrode of the driving transistor corresponding to a first scan signal;

an initialization transistor configured to apply an initialization voltage to the gate electrode of the driving transistor according to a second scan signal during an initialization period;

an assistance transistor configured to apply an assistance voltage to the bias electrode of the driving transistor according to the second scan signal during the initialization period; and

a storage capacitor including a first electrode connected to the gate electrode of the driving transistor and a second electrode connected to a first power source voltage.

13. The organic light emitting diode (OLED) display of claim 12, wherein the second scan signal is transmitted to the scan line previous to the scan line receiving the first scan signal.

14. The organic light emitting diode (OLED) display of claim 12, wherein the plurality of pixels comprise:

a threshold voltage compensation transistor configured to operate according to the first scan signal after the initialization period to diode-connect the gate electrode and the drain electrode of the driving transistor and to compensate for a threshold voltage of the driving transistor; and

at least one light emission control transistor connected between a supply source of the first power source voltage and the organic light emitting diode (OLED) and including a gate electrode configured, to receive a light emission control signal to control the light emission of the organic light emitting diode (OLED).