OLED Passivation Layer Segmentation for Color Uniformity
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Solution Overview
Problem
Inorganic films under the emission layer of OLED devices deteriorate viewing angle characteristics and color uniformity, particularly when implementing white light, which is a challenge in manufacturing OLEDs with broader viewing angles and better color uniformity.
Innovation Solution
The OLED device incorporates red, green, blue, and white subpixels with a substrate, thin film transistor active layer, overcoat layer, and passivation layer, where the passivation layer is either absent in the light path or formed as a single layer of silicon nitride, preventing color uniformity reduction and maintaining good color uniformity by positioning the overcoat layer, interlayer insulating layer, and gate insulating layer under the first electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is formed under the emission layer to protect the TFT, then device reliability is improved, but color uniformity and viewing angle characteristics deteriorate
Solution Approach 1:
The passivation layer is segmented into two regions: a first passivation layer in the light emission path and a second passivation layer outside the light emission path. This segmentation allows the first layer to be optimized for optical performance (thin or absent) while the second layer provides comprehensive device protection, resolving the contradiction between reliability and color uniformity.
Solution Approach 2:
Different regions of the device are assigned different passivation layer configurations tailored to their specific functional requirements. The light emission path region uses a thin or absent passivation layer to maintain color uniformity, while other regions use a standard passivation layer for protection, achieving local optimization of both reliability and optical quality.
2Reliability
If inorganic films are formed under the emission layer for device protection, then reliability is improved, but viewing angle characteristics deteriorate
Solution Approach 1:
The passivation structure is divided into spatial segments: a first passivation layer positioned in the light path that is thin or absent to preserve viewing angle characteristics, and a second passivation layer positioned outside the light path that provides robust device protection. This segmentation resolves the contradiction between reliability and viewing angle performance.
Solution Approach 2:
The emission layer serves as an intermediary between the passivation layers and the external environment, providing protection to the TFT while allowing light to pass through to the viewer. The first passivation layer (thin or absent) and second passivation layer work together through this intermediary to achieve both device protection and good viewing angle characteristics.
3Reliability
If multiple passivation layers are formed to ensure device protection, then reliability is improved, but device complexity increases
Solution Approach 1:
The passivation function is segmented into two distinct layers with different thicknesses and positions. The first passivation layer (thin or absent) is positioned in the light path where it would otherwise degrade optical performance, while the second passivation layer is positioned outside the light path to provide protection. This segmentation achieves reliable device protection without significantly increasing overall structural complexity.
Solution Approach 2:
Different passivation layer configurations are applied locally based on functional requirements. The first passivation layer uses a thin or absent configuration in the light emission path to maintain optical quality, while the second passivation layer uses a standard configuration in non-light-path regions for protection. This local differentiation optimizes the balance between reliability and 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 configuration improves color uniformity and viewing angle characteristics by preventing the passivation layer from interfering with light emission, reducing the occurrence of the 'wiggle phenomenon and maintaining good color uniformity of white light, thereby enhancing the overall performance of OLED devices.
Implementation Method 1
Holes supplied from the first electrode and electrons supplied from the second electrode are bonded together in the emission layer to form the exciton, which is a pair of a hole and an electron, and the OLED device emits light by the energy generated when the exciton returns to a bottom level.
Data Source
AI summary
The present invention further relates to an OLED device, including R, G, B, and W subpixels. Specifically, the OLED device comprises a substrate; a thin film transistor (TFT) active layer disposed on the substrate, comprising a gate electrode, a gate insulating layer, an active layer, an interlayer insulating layer, a source electrode, and a drain electrode; an overcoat layer disposed over the thin film transistor; and a passivation layer disposed between the thin film transistor and the overcoat layer, wherein the passivation layer is absent in a path of a light or wherein the passivation layer is disposed in the path of the light as a single layer comprising silicon nitride.