Display with redundant light emitting devices
An active matrix display where in one embodiment each cell comprises: a driving circuit for providing current to light emitting devices placed in the cell under the control of a data driver signal, a first light emitting device location connected to the driving circuit and a second light emitting device location connected in series to the first light emitting device location. A first thin-film transistor (TFT) is connected in parallel with the first light emitting device location and a second TFT is connected in parallel with the second light emitting device location, its gate node connected to the gate node of the first TFT. One terminal of a third TFT is connected to the gate nodes of the first and second TFTs and selectively connects a control signal to the first and second TFTs under the control of a scan driver signal. The control signal determines which of a first or second light emitting device placed in the cell emits light when the driving circuit provides current.
1. A method of populating a display, comprising:
placing first light emitting devices in a plurality of cells of the display;
testing the display to determine whether one or more of the first light emitting devices in the plurality of cells are defective;
placing a second light emitting device in each of the plurality of cells determined to contain a defective first light emitting device; and
programming the display to emit light by the second light emitting device in each of the plurality of cells determined to contain the defective first light emitting device.
2. The method of claim 1 , further comprising programming the display to emit light by a first light emitting device in cells other than the plurality cells determined to contain the defective first light emitting device.
3. The method of claim 1 , wherein the second light emitting device is a known good light emitting device.
4. The method of claim 1 , further comprising:
subsequent to placing the second light emitting device, testing the display to determine whether the second light emitting device is defective; and
placing a third light emitting device in a cell determined to contain a defective second light emitting device.
5. The method of claim 4 , wherein testing the display includes providing control signals of opposite polarity to the first light emitting device and the second light emitting device.
6. The method of claim 4 , further comprising programming the display to emit light by the third light emitting device in the cell determined to contain the defective second light emitting device.
7. The method of claim 4 , wherein:
the cell operates in a plurality of modes;
in a first mode, a first light emitting device is activated;
in a second mode, in the second light emitting device is activated;
in a third mode, a third light emitting device location is activated; and
in a fourth mode of operation, each of the first light emitting device, the second light emitting device, and the third light emitting device is deactivated.
8. The method of claim 7 , wherein in a fourth mode of operation, each of the first light emitting device, the second light emitting device, and the third light emitting device is activated.
9. The method of claim 4 , further comprising:
subsequent to placing the third light emitting devices, testing the display to determine whether the placed third light emitting device is defective; and
programming the display to disable the cell containing the third light emitting device determined to be defective.
10. The method of claim 1 , wherein the first light emitting device and the second light emitting device in each of the plurality of cells are connected in series.
11. The method of claim 1 , wherein the first light emitting device and the second light emitting device in each of the plurality of cells are connected in parallel.
12. The method of claim 1 , further comprising:
subsequent to placing the second light emitting device, testing the display to determine whether the placed second light emitting device is defective; and
programming the display to disable a cell containing the defective second light emitting device.
13. The method of claim 1 , wherein the first light emitting devices and the second light emitting device are inorganic light emitting devices.