OLED Light Extraction via Refractive Index Mediator
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Solution Overview
Problem
Organic light-emitting display apparatuses face inefficiencies in light extraction due to total reflection at interfaces with external air, leading to reduced front light efficiency and visibility degradation.
Innovation Solution
Incorporating a refractive layer with a higher refractive index than the insulating and pixel defining layers, positioned between the insulating layer and the pixel defining layer, to form an optical waveguide that reduces light loss by total reflection and enhances light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional organic light-emitting display apparatus is used, then the device structure is simple, but light extraction efficiency is reduced due to total reflection at interfaces with external air
Solution Approach 1:
A refractive layer with refractive index n3 is introduced as an intermediary between the insulating layer (refractive index n1) and the pixel defining layer (refractive index n2). This intermediate layer with higher refractive index acts as a mediator to reduce total reflection at the interfaces, thereby improving light extraction efficiency without significantly complicating the device structure
Solution Approach 2:
The refractive index parameter is strategically modified by introducing a layer with refractive index n3 > n2 > n1. This parameter change in the optical properties of the layers creates favorable refraction conditions that reduce total internal reflection and improve light extraction efficiency
2Loss of energy
If the refractive layer is added to improve light extraction, then light extraction efficiency increases, but device complexity increases
Solution Approach 1:
The refractive layer is selectively positioned only in regions where it is most needed for light extraction enhancement - specifically between the insulating layer and pixel defining layer at the interfaces where total reflection occurs. This localized application improves light extraction without requiring modification of the entire device structure
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
The refractive layer configuration increases the amount of incident light transmitted and reduces angular range of light release, improving light extraction efficiency and preventing visibility degradation by minimizing light loss at the interface with external air.
Implementation Method 1
inefficiencies in light extraction due to total reflection at interfaces with external air
Implementation Method 2
The refractive layer has a refractive index greater than that of both the insulating layer and the pixel defining layer
Data Source
AI summary
An organic light-emitting display apparatus including a substrate; an insulating layer disposed on the substrate; a first pixel electrode disposed on the insulating layer and including a reflecting layer; a pixel defining layer disposed around one end of the first pixel electrode and extending away from the first pixel electrode; a first intermediate layer disposed on the first pixel electrode and including an organic emission layer; an opposite electrode disposed on the first intermediate layer and the pixel defining layer and including a reflecting layer; and a first refractive layer disposed between the insulating layer and the pixel defining layer and having a refractivity greater than that of the insulating layer and the pixel defining layer. A first end of the first refractive layer is disposed to contact the first intermediate layer, and a second end of the refractive layer is disposed to face a portion of the opposite electrode.