System and methods for extracting correlation curves for an organic light emitting device

• US 10,176,736 B2
• Filed: 06/25/2014
• Issued: 01/08/2019
• Est. Priority Date: 02/04/2010
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza
• Primary Examiner(s): Natalini, Jeff
• Application Number:
  US14/314,514
• Publication Number:
  US 20140306868A1
• Time in Patent Office: 1,658 Days
• CPC Class Codes: G09G 2300/0413 Details of dummy pixels or dummy lines in flat panels
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

A system determines the efficiency degradation of organic light emitting devices (OLEDs) in multiple array-based semiconductor devices having arrays of pixels that include OLEDs. The system determines the relationship between changes in an electrical operating parameter of the OLEDs and the efficiency degradation of the OLEDs in each of the array-based semiconductor devices, uses the determined relationship for a selected one of the array-based semiconductor devices to determine the efficiency degradation of the OLEDs, and compensates for the efficiency degradation. The relationship between changes in an electrical operating parameter of the OLEDs and the efficiency degradation of the OLEDs in the array-based semiconductor devices may be determined by the use of a test OLED associated with each of the devices.

Claims

1. A method of determining the efficiency degradation of organic light emitting devices (OLEDs) and compensating for said deficiency in multiple array-based semiconductor display devices having arrays of pixels that include OLEDs each of the array-based semiconductor display devices further comprising a controller and a readout circuit, said method comprising:

storing a library of interdependency curves in memory of each of the array-based semiconductor display devices, said interdependency curves directly relating changes in an electrical operating parameter for one or more reference OLED pixels to the efficiency degradation of said one or more reference OLED pixels for a plurality of stress conditions;

for each of the array-based semiconductor display devices in operation, using the controller thereof to;

a) control the readout circuit thereof to periodically measure the electrical operating parameter for at least one OLED in at least one of the pixels of the array-based semiconductor display devices, determine a change in said electrical operating parameter from a baseline value, and store the change in the memory;

b) calculate the rate of change of the electrical operating parameter based on a current value of the change and one or more previously recorded values of the change;

c) determine a stress condition of the at least one OLED using the calculated rate of change of the electrical operating parameter for the at least one OLED;

d) select at least one interdependency curve from the stored library based on the determined stress condition,

e) determine the efficiency degradation of the at least one OLED based on the at least one interdependency curve, and

f) modify a programming voltage or current for the at least one of the pixels to compensate for said efficiency degradation.

2. The method of claim 1 wherein the libraries of the interdependency curves stored with the display devices comprise interdependency curves that are obtained by the controllers measuring one or more test OLEDs in each of the respective array-based semiconductor display devices using a readout circuit of the display and one or more optical sensors coupled to said one or more test OLEDs.

3. The method of claim 1 wherein the arrays of pixels of the multiple array-based semiconductor display devices are fabricated from a same substrate, the substrate further including one or more test OLED devices, the method comprising:

using one or more photo sensors optically coupled to the one or more test OLED devices and a readout circuit electrically coupled to the one or more test OLED devices to obtain a set of interdependency curves for a set of different stress conditions, each of said interdependency curves directly relating changes in the electrical operating parameter of the one or more test OLED devices to the efficiency degradation thereof at one of the stress conditions, and

storing the set of interdependency curves in the library of interdependency curves of each array based semiconductor display.

4. The method of claim 3 wherein the one or more photo sensors are comprised within said one or more test OLED devices.

5. The method of claim 3 comprising, for at least one of the array-based semiconductor display devices in operation:

i) measuring a test OLED comprised in said at least one array-based semiconductor display,

ii) identifying an interdependency curve from the library that has the closest aging behavior to said measured test OLED,

iii) comparing the difference between the aging behaviors of said identified interdependency curve and said measured test OLED with a predetermined threshold, and

iv) if said difference exceeds said threshold, using the test OLED to obtain a new interdependency curve and updating the library of interdependency curves stored with the display.

6. The method of claim 5 comprising using said identified interdependency curve to compensate for the efficiency degradation of the display containing said measured test OLED if said difference is less than said threshold.

7. The method of claim 1 in which the controller in at least one of the display devices compares the rate of change and the change determined in steps (a) and (b) to stored values thereof to determine the stress condition.

8. The method of claim 1 further comprising, for at least one of the array-based semiconductor display devices in operation, measuring a test OLED comprised in said at least one array-based semiconductor display device, generating an interdependency curve that corresponds to the measurements of said test OLED in said array-based semiconductor display device, and updating the library of interdependency curves in said at least one of the array-based semiconductor display devices with the interdependency curve generated from the measurements of said test OLED.