OLED Pixel Unit Optical Compensation for Luminance Uniformity
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Solution Overview
Problem
The luminance uniformity of OLED displays is affected by the drift in threshold voltages of driving transistors in different pixel units, leading to inconsistencies in light emission, which existing compensation methods fail to adequately address.
Innovation Solution
A pixel unit is designed with a photosensitive element and a switch circuit that senses light intensity and adjusts light-emitting control data based on sensed signals, allowing for external control of luminance through a compensation method that involves optical and electrical compensation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal or external electrical compensation is used to guarantee luminance uniformity, then threshold voltage drifts can be compensated, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The pixel unit uses its own light-emitting element to generate test light that is sensed by the photosensitive element within the same pixel unit. This self-service approach eliminates the need for external compensation circuits, allowing the pixel to autonomously measure and compensate for threshold voltage drifts without adding device complexity
Solution Approach 2:
The light-emitting element serves dual functions: it acts as both the display element that emits light for viewing and the light source for threshold voltage compensation measurements. This multi-functionality eliminates the need for separate test light sources and reduces overall device complexity while maintaining luminance uniformity
2Reliability
If a photosensitive element is added to each pixel unit for sensing light intensity, then luminance uniformity can be improved, but the area of the pixel unit increases
Solution Approach 1:
The photosensitive element is integrated within the same pixel unit as the light-emitting element, and both share common electrodes and circuit elements. The anode of the light-emitting element serves as the cathode of the photosensitive element, and the cathode serves as the anode, merging multiple functions into a single integrated structure that minimizes area occupation
Solution Approach 2:
The photosensitive element is nested within the pixel unit structure, with its electrodes and components overlapping or sharing space with the light-emitting element and driving circuitry. This nesting arrangement allows the photosensitive element to be accommodated without significantly increasing the overall pixel unit area
3Measurement precision
If multiple electrode layers and conductive materials are used in the photosensitive element, then sensing precision is improved, but the manufacturing process complexity increases
Solution Approach 1:
The same transparent conductive oxide layer serves as both the anode of the photosensitive element and the cathode of the light-emitting element, and the light-shielding material layer serves as both the cathode of the photosensitive element and part of the light-emitting element structure. This multi-functionality reduces the number of separate manufacturing steps while maintaining sensing precision
Solution Approach 2:
The manufacturing processes for the photosensitive element and light-emitting element are merged into a single integrated fabrication sequence. The electrodes and conductive layers are formed in the same processing steps, eliminating the need for separate photolithography and deposition steps that would increase manufacturing complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution improves luminance uniformity and extends the service life of OLED displays by compensating for changes in self-illuminating efficiency through external calculation and adjustment of light-emitting control data, ensuring consistent light emission across pixel units.
Implementation Method 1
the photosensitive element is configured to sense a light intensity of the light emitted by the light-emitting circuit and to output a sensed light intensity signal
Data Source
AI summary
A pixel unit, a compensation method of the pixel unit, a display device and a manufacturing method of the display device are disclosed. The pixel unit includes a light-emitting circuit configured to emit light under control of an external control circuit, a photosensitive element configured to sense a light intensity of light emitted by the light-emitting circuit and to output a sensed light intensity signal by a sensing output terminal, and a switch circuit configured to control an ON/OFF state between the sensing output terminal and the external control circuit.