OLED Transistor Aging Circuit for Off-Current Reduction
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Solution Overview
Problem
Display devices, such as those using organic light emitting diodes, suffer from off-current issues in transistors during turn-off states, leading to unwanted light emission and defects like mura, which affect image quality, especially at low grayscale levels.
Innovation Solution
A display device and driving method that include an aging frame where transistors are aged before image display, with specific voltage control periods to reduce off-currents, ensuring transistors are in a turn-off state with a significant potential difference, thereby preventing dark spots and improving transistor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors are used in display pixels without aging treatment, then device complexity is reduced, but off-current increases causing mura defects and dark spots
Solution Approach 1:
The patent applies preliminary aging treatment to transistors before they are used in normal display operation. An aging circuit is configured with transistors that undergo aging treatment in advance through specific voltage application sequences, ensuring they meet off-current specifications before being activated in pixel circuits, thereby preventing mura defects without complicating the main display driving circuitry.
Solution Approach 2:
The patent divides the transistor aging function into separate aging circuits distinct from the normal display driving circuits. The aging circuits include dedicated aging transistors, capacitors, and voltage application paths that operate independently from the pixel driving circuits, allowing aging treatment without interfering with normal display operation or increasing overall system complexity.
2Reliability
If aging treatment is applied to all transistors, then transistor reliability improves, but manufacturing process complexity increases
Solution Approach 1:
The patent applies aging treatment selectively to specific transistors that require it based on their functional requirements. Not all transistors in the display device undergo aging treatment - only those in critical positions where off-current would cause visible defects. This localized approach ensures reliability where needed while keeping the manufacturing process simple for other components.
Solution Approach 2:
The aging treatment is integrated into the manufacturing process as a preliminary step before final assembly. The aging circuits are formed simultaneously with other display device components through the same manufacturing processes, and the aging treatment itself is applied before the device is put into service, eliminating the need for separate post-manufacturing aging steps.
3Manufacturing precision
If transistors operate without preliminary aging, then productivity is higher, but image quality deteriorates due to mura defects
Solution Approach 1:
The patent performs aging treatment during the manufacturing process before the display device is activated for normal use. By the time the device is shipped and activated, all aging treatment is already complete, so end-users experience immediate high-quality display without any delay. The aging process occurs offline during production, not during actual device operation.
Solution Approach 2:
The aging treatment is applied in controlled periodic cycles during manufacturing, with specific voltage application sequences and timing. This structured approach ensures consistent aging results across all transistors while maintaining efficient production flow, achieving both display uniformity and manufacturing productivity.
Data Source
AI summary
A display device includes a plurality of pixels, each of the pixels including an organic light emitting diode and a plurality of transistors configured to control a current applied to the organic light emitting diode, wherein an aging frame includes an aging period in which at least one of the plurality of transistors is aged, wherein at least one of the plurality of transistors is in a turn-off state in the aging period, and wherein a potential difference between one electrode and an other electrode of a transistor of the plurality of transistors is equal to or greater than a reference potential difference, the reference potential difference being a difference value between a high level and a low level of a first power source voltage.