P-type Dopant Blue Light Absorption in Organic Electronic Elements
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Solution Overview
Problem
Organic electronic elements used in portable display devices face challenges in achieving high light extraction efficiency and luminous efficiency due to the low intensity and efficiency of light emitted from light emitting units as it passes through multiple layers, particularly with high absorption rates of blue wavelength light by conventional p-type dopants in charge generating and hole injection layers.
Innovation Solution
Incorporating a p-type dopant with a low absorption rate for the blue wavelength band in the charge generating layer and hole injection layer, represented by specific compounds, to reduce absorbance and enhance light extraction and luminous efficiency in organic electronic elements, display panels, and display devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional p-type dopants are used in charge generating layer and hole injection layer, then charge injection and transport are achieved, but blue light absorption is high which reduces light extraction efficiency and luminous efficiency
Solution Approach 1:
The patent changes the chemical structure parameters of the p-type dopant by introducing electron-withdrawing groups (cyano groups, carbonyl groups, or halogen atoms) at specific positions in the molecular structure. This parameter change reduces the HOMO energy level and modifies the absorption spectrum, resulting in lower blue light absorbance while maintaining charge injection and transport functions. The specific structural parameters (substituent types, their positions, and combinations) are optimized to achieve the desired optical and electrical properties.
Solution Approach 2:
The patent employs composite material design by combining specific host materials with the newly designed p-type dopant molecules that contain electron-withdrawing groups. This composite approach allows the dopant to function effectively in charge generation and transport while its modified optical properties reduce blue light absorption. The synergistic combination of host and dopant materials achieves both electrical performance and improved light extraction efficiency.
2Productivity
If light passes through multiple layers of organic electronic element, then charge transport and light emission occur, but light intensity and efficiency are reduced due to repeated absorption
Solution Approach 1:
The patent modifies the optical parameters of the p-type dopant by introducing electron-withdrawing groups that shift the absorption spectrum away from the blue wavelength region. This parameter change reduces the overlap between the dopant absorption spectrum and the emitted light spectrum, minimizing re-absorption losses as light traverses multiple layers. The modified dopant maintains its charge transport function while its optical properties are optimized to reduce energy loss through repeated absorption cycles.
3Illumination intensity
If multi-stack structure is used to improve light emission, then more light emitting units are available, but light intensity decreases due to multiple layers of absorption
Solution Approach 1:
The patent uses composite material design where the p-type dopant with electron-withdrawing groups is combined with appropriate host materials in each stack layer. This composite structure ensures that each layer contributes to light emission while the modified dopant's reduced blue light absorbance minimizes cumulative absorption losses across multiple stacks. The composite approach allows optimization of both charge transport and optical properties in each layer.
Solution Approach 2:
The patent applies parameter changes to the dopant's optical properties through strategic placement of electron-withdrawing groups, which shifts the absorption edge and reduces absorption coefficient in the blue region. This enables the multi-stack structure to maintain high light emission intensity by reducing the absorption parameter in each layer, thereby minimizing the cumulative effect of multiple absorption events across stacks.
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 use of p-type dopants with low absorption rates in these layers improves light extraction efficiency and luminous efficiency by reducing blue light absorbance, leading to increased efficiency and reduced driving voltage, as demonstrated in comparative evaluations.
Implementation Method 1
The intensity and efficiency of the lights generated from the light emitting unit are low while repeatedly passing through the layers of the organic electronic element
Data Source
AI summary
An organic electronic element, a display panel and a display device can each include a charge generating layer and a hole injection layer including a p-type dopant with low absorption rate for a blue wavelength band so that they can have excellent light extraction efficiency or luminous efficiency.