OLED Hole Connection Layer Segmentation for Charge Balance
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Solution Overview
Problem
The existing organic light emitting device structures face challenges in optimizing charge balance, leading to charge accumulation and exciton quenching, which affects the stability and color characteristics of OLED devices, particularly in red and green soluble hybrid OLEDs with bipolar hole connection layers.
Innovation Solution
The introduction of a substrate with three light emitting parts, each having a hole transport layer, light emitting layers, and a common third light emitting layer with a bipolar hole connection layer that includes both bipolar and electron transport materials, optimizing the charge balance and recombination zones within the light emitting layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bipolar hole connection layer is used in red and green soluble hybrid OLED devices, then the device structure is simplified and manufacturing is easier, but charge accumulation occurs at the interface between light emitting layer and hole connection layer, causing exciton quenching and reduced device lifetime
Solution Approach 1:
The hole connection layer is segmented into multiple layers with different functions: a first hole connection layer containing only hole transport material positioned adjacent to the light emitting layer, and a second hole connection layer containing bipolar material positioned between the first hole connection layer and the common light emitting layer. This segmentation prevents charge accumulation at critical interfaces while maintaining manufacturing simplicity.
Solution Approach 2:
Different regions of the hole connection structure use different materials with specific properties: the first hole connection layer uses pure hole transport material to prevent electron injection and charge accumulation at the light emitting layer interface, while the second hole connection layer uses bipolar material for balanced charge transport. This local differentiation resolves the contradiction between ease of manufacture and device lifetime.
2Ease of manufacture
If a bipolar hole connection layer is used, then the device structure is simplified, but deep blue wavelengths are limited in the hole connection layer, degrading color characteristics of the OLED device
Solution Approach 1:
The hole connection structure is divided into two functional layers: the first hole connection layer with pure hole transport material that does not emit deep blue wavelengths, and the second hole connection layer with bipolar material. This segmentation eliminates unwanted deep blue emission from the hole connection layer while maintaining structural simplicity.
Solution Approach 2:
The first hole connection layer is specifically designed with pure hole transport material that lacks deep blue emission characteristics, placing it at the critical interface with the light emitting layer. This local material selection prevents color characteristic degradation while keeping the overall device structure simple and easy to manufacture.
3Productivity
If HTL, hole connection layer, blue common layer, ETL, and EIL are commonly used, then large-area processing is enabled, but charge balance optimization becomes difficult to implement
Solution Approach 1:
The hole connection functionality is segmented into two distinct layers with different material compositions and functions, enabling independent optimization of charge balance in each layer while maintaining the common-layer structure for large-area processing.
Solution Approach 2:
The dual-layer hole connection structure provides dynamic control over charge balance: the first layer handles hole transport adjacent to the light emitting layer, while the second layer with bipolar material balances electron and hole transport. This dynamic functionality enables charge balance optimization without complicating the overall manufacturing process for large-area devices.
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 the efficiency of light emission, extends the lifetime, and enhances the color coordinates of OLED devices by shifting recombination zones away from the interfaces, reducing exciton quenching and improving charge injection characteristics.
Implementation Method 1
an organic light emitting device (hereinafter, referred to as OLED) is an electronic device that emits light in response to an applied potential
Data Source
AI summary
Disclosed is an organic light emitting device that may include a substrate having first to third light emitting parts; a first electrode in each of the first to third light emitting parts; a hole transport layer on the first electrode; first and second light emitting layers on the hole transport layer in the first and second light emitting parts, respectively; a common third light emitting layer on the first and second light emitting layers; a hole connection layer including a bipolar material and an electron transport material, wherein the hole connection layer in the first and second light emitting parts is provided between the common third light emitting layer and the first and second light emitting layers, and the hole connection layer in the third light emitting part is provided between the common third light emitting layer and the hole transport layer; a second electrode on the common third light emitting layer.