Tand OLED Charge Transport Layer Polarity Reduction
Solution Overview
Problem
Existing organic light-emitting devices with tandem structures face issues of reduced luminous efficiency and short operating lifetime due to hole mobility in the electron transport layer and deterioration of the charge generation layer, particularly with the diffusion of n-type dopants into the charge transport layer.
Innovation Solution
Incorporating a fused polycyclic hydrocarbon compound in the charge transport layer between the light-emitting layers and the charge generation portion, which reduces the polarity and diffusion of n-type dopants, thereby improving the operating lifetime and maintaining the charge injection/transport performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If hole mobility in the electron transport layer is reduced to prevent holes from passing through, then luminous efficiency is improved, but the electron transport layer becomes susceptible to deterioration due to energization
Solution Approach 1:
A hole transport layer is introduced as an intermediary between the electron transport layer and the charge generation layer. This hole transport layer selectively transports holes away from the electron transport layer, preventing hole accumulation and energization-induced deterioration in the electron transport layer while maintaining high luminous efficiency by controlling charge distribution.
2Reliability
If n-type dopant concentration is increased in the charge generation layer to improve charge injection, then charge injection performance is improved, but the dopant diffuses into the charge transport layer causing deterioration
Solution Approach 1:
The hole transport layer serves as a protective intermediary that prevents n-type dopant diffusion from the charge generation layer into the charge transport layer. By positioning this layer between them, the patent blocks the diffusion path while maintaining effective charge injection performance through the charge generation layer.
Solution Approach 2:
The hole transport layer extracts and transports holes away from the charge generation layer interface, preventing the interaction between holes and n-type dopants that would otherwise cause dopant diffusion into the charge transport layer. This separation of functions protects the charge transport layer composition.
3Productivity
If the charge generation layer contains both n-type and p-type charge generation layers to improve carrier supply, then internal quantum efficiency is improved, but the device complexity increases
Solution Approach 1:
The hole transport layer performs multiple functions: it transports holes from the charge generation layer, prevents hole accumulation in the electron transport layer, and blocks n-type dopant diffusion into the charge transport layer. This multi-functionality improves internal quantum efficiency without proportionally increasing device 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 significantly enhances the operating lifetime of the tandem organic light-emitting device by preventing n-type dopant diffusion and maintaining efficient charge injection and transport, leading to improved luminous efficiency and durability.
Implementation Method 1
Incorporating a fused polycyclic hydrocarbon compound in the charge transport layer between the light-emitting layers and the charge generation portion, which reduces the polarity and diffusion of n-type dopants
Implementation Method 2
Excitons generated in the light-emitting layer emit light upon returning to the ground state
Data Source
AI summary
An organic light-emitting device includes, in sequence, a first electrode, a first light-emitting layer, a charge transport layer, a charge generation portion, a second light-emitting layer, and a second electrode. The charge transport layer contains a fused polycyclic hydrocarbon compound.