OLED Display Structured Electrode Leakage Current
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Solution Overview
Problem
Organic light-emitting diode (OLED) displays experience pixel cross-talk due to leakage current between adjacent pixels, degrading display performance and causing color-shift, primarily because of the conductivity of OLED layers allowing voltage applied to one pixel to affect neighboring pixels.
Innovation Solution
Reducing the thickness of OLED layers such as the hole transport layer and electron transport layer while maintaining a predetermined optical cavity distance by using optical spacers or Distributed Bragg Reflectors, and decoupling the reflector's functions to enhance electrical performance without compromising optical performance, along with separate patterning of anodes and electron blocking layers to minimize leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the thickness of OLED layers is reduced to decrease lateral conductivity and leakage current, then pixel cross-talk is reduced, but the optical cavity distance cannot be maintained which degrades optical performance
Solution Approach 1:
The patent segments the reflector structure into multiple components: a bottom reflector layer and a top reflector layer separated by an optical cavity. This segmentation allows independent optimization of electrical and optical functions. The bottom reflector layer provides electrical isolation to reduce leakage current, while the top reflector layer maintains optical cavity distance for optimal optical performance, resolving the contradiction between reducing leakage and maintaining optical performance.
Solution Approach 2:
The patent introduces an optical cavity as an intermediary structure between the bottom and top reflector layers. This optical cavity serves as a mediator that maintains the predetermined optical distance required for optimal optical performance while allowing the OLED active layer thickness to be reduced for electrical isolation. The cavity acts as a buffer that decouples the electrical and optical requirements.
2Reliability
If the OLED layers are made thinner to reduce conductivity and improve electrical isolation, then cross-talk between pixels is reduced, but the distance for optimal optical cavity effect cannot be maintained
Solution Approach 1:
The reflector is segmented into bottom and top layers with an optical cavity between them. The bottom reflector layer is positioned close to the OLED active layer to provide electrical isolation and reduce cross-talk, while the top reflector layer is positioned at the optimal distance to maintain the optical cavity effect for maximum illumination intensity. This segmentation resolves the contradiction between electrical isolation and optical performance.
Solution Approach 2:
The patent adds a vertical dimension to the reflector structure by creating a layered configuration with an optical cavity. Instead of using a single planar reflector, the solution introduces height and depth dimensions through the cavity structure, allowing simultaneous optimization of both electrical isolation (achieved through the bottom reflector layer) and optical performance (achieved through the top reflector layer at optimal distance).
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 approach significantly reduces lateral leakage current and pixel cross-talk, improving display efficiency and maintaining optical performance by independently tuning the electrical and optical cavities, thereby enhancing the overall display quality.
Implementation Method 1
the distance between the reflector layer and the top surface of the anode is selected to maintain a predetermined optical cavity distance for the display
Implementation Method 2
grating structures protruding from the reflector layer into the transparent optical spacer may be provided to enhanced emission at one or more targeted display viewing angles
Implementation Method 3
photonic crystal structures embedded within the transparent optical spacer may be provided to enhance emission at one or more targeted display viewing angles
Implementation Method 4
The transparent optical spacer may also be substituted by a Distributed Bragg Reflector to help enhance the reflectivity of the reflector layer
Data Source
AI summary
A display may have an array of organic light-emitting diode (OLED) pixels that each have OLED layers interposed between a cathode and an anode. Voltage may be applied to the anode of each pixel to control the magnitude of emitted light. The conductivity of the OLED layers may allow leakage current to pass between neighboring anodes in the display. To reduce leakage current and cross-talk, the thickness of at least one of the OLED layers may be reduced. To maintain the optical cavity of the pixels, transparent optical spacer structures may be inserted. Alternatively, the thickness of the anodes can be increased. To accommodate a common prime layer within the OLED layers, the optical spacers or anodes may be separately patterned to have different thicknesses. Grating structures and photonic crystal structures may be embedded as part of the optical spacers to help control emission at selected viewing angles.