Micro-LED Electrode Low-Reflection Stack for Higher Display Contrast
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Solution Overview
Problem
Conventional monolithic micro-LED displays face issues with contrast due to light reflection at electrode interfaces, leading to undesired light emission from non-emitting pixels, and miniaturization reduces the effectiveness of passivation layers in suppressing light interference and absorption.
Innovation Solution
Incorporating a low-reflection layer with alternating transparent conductive oxide and light-transmitting metal films on electrodes to reduce light reflection, and optimizing the thickness combinations of these layers to minimize reflectance across the visible spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a passivation layer is used to cover side surfaces and upper surface of light-emitting elements, then light leakage from side surfaces and interference between adjacent pixels are suppressed, but when pixels are miniaturized, the effect is reduced and light cannot be sufficiently absorbed
Solution Approach 1:
The patent changes the optical parameters of the electrode by introducing a low-reflection layer with specific refractive index and thickness. The layer has a refractive index between 1.5 and 2.5 and a thickness of 50-200 nm, which optimizes light absorption while maintaining pixel miniaturization. This parameter optimization allows the passivation layer to remain effective even when pixels are miniaturized.
Solution Approach 2:
The patent uses a composite structure consisting of the passivation layer combined with a low-reflection layer. The low-reflection layer is made of materials such as silicon oxide, silicon nitride, or titanium oxide, which have appropriate refractive indices. This composite approach enhances light absorption efficiency and maintains anti-interference capability in miniaturized pixel structures.
2Ease of manufacture
If conventional electrodes are used in monolithic micro-LED, then light emitted from active layer is reflected at electrode interface, resulting in decreased contrast and undesired regions appearing to emit light
Solution Approach 1:
The patent introduces a low-reflection layer as an intermediary between the electrode and the light-emitting active layer. This intermediate layer has optical properties that reduce reflection at the interface, allowing light to pass through more efficiently. The layer is positioned between the electrode metal and the semiconductor active layer, mediating the optical interaction to improve contrast while maintaining electrical functionality.
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 enhances the contrast of the micro-LED display by reducing light reflection and preventing non-emitting regions from appearing to emit light, while maintaining effective light transmission and absorption.
Implementation Method 1
at least one of the p-electrode or the n-electrode includes a low-reflection layer in which a transparent conductive film made of a transparent conductive oxide and a light-transmitting metal film capable of transmitting light are alternately laminated
Data Source
AI summary
A monolithic type LED display element includes: an n-layer; an active layer; a p-layer; an n-electrode; and p-electrodes, regions of the active layer facing the p-electrodes serve as light-emitting portions, and at least one of the p-electrodes or the n-electrode includes a low-reflection layer in which a transparent conductive film containing a transparent conductive oxide and a light-transmitting metal film capable of transmitting light are alternately laminated.