Pyrimidine Derivative Electron Transport Layer for OLED Voltage Reduction
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Solution Overview
Problem
Multilayer organic light emitting display devices with charge generation layers experience increased operating voltage and decreased efficiency, particularly when N-type charge generation layers are doped with alkali metals, leading to reduced lifetime and electron injection issues due to energy level differences.
Innovation Solution
Incorporating a pyrimidine derivative as an electron transport layer with high electronegativity in at least one of the light emitting parts, which facilitates charge transport and reduces operating voltage while improving efficiency by enhancing electron mobility and injection properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a multilayer emitting structure with charge generation layers is used, then device lifetime is improved, but operating voltage increases and efficiency decreases
Solution Approach 1:
The patent modifies the energy level parameters of the charge generation layers by selecting materials with specific HOMO and LUMO levels. The P-type CGL uses materials with HOMO levels of 5.8-6.5 eV, while the N-type CGL uses materials with LUMO levels of 2.0-3.0 eV, creating optimized energy level梯度的 that reduces voltage requirements while maintaining device lifetime
Solution Approach 2:
The patent employs composite material structures where the charge generation layers are composed of multiple organic compounds with complementary properties. The P-type CGL combines materials like TCTA and TAPC, while the N-type CGL combines materials like BCP and TPBi, creating synergistic effects that simultaneously improve lifetime and reduce operating voltage
2Duration of action of stationary object
If a multilayer emitting structure with charge generation layers is used, then device lifetime is improved, but emission efficiency decreases
Solution Approach 1:
The patent optimizes the thickness parameters of the charge generation layers to balance lifetime and efficiency. The P-type CGL is designed with thickness of 5-20 nm and the N-type CGL with thickness of 5-15 nm, creating optimal charge distribution that enhances emission efficiency while maintaining long device lifetime through the multilayer structure
Solution Approach 2:
The patent applies different material compositions and thicknesses to different regions of the charge generation layers. The P-type CGL uses materials with higher hole mobility near the anode interface, while the N-type CGL uses materials with higher electron mobility near the cathode interface, creating locally optimized charge transport that improves overall emission efficiency
3Productivity
If the N-type charge generation layer is doped with alkali metal or alkali earth metal, then charge generation is enhanced, but device lifetime decreases
Solution Approach 1:
The patent extracts and eliminates the harmful doping approach by completely avoiding the use of alkali metals and alkali earth metals in the charge generation layers. Instead, it relies on undoped organic compounds with inherently suitable energy levels, thereby preventing the lifetime degradation caused by metal doping while maintaining effective charge generation
Solution Approach 2:
The patent replaces the unstable doped structure with stable undoped organic compounds that have appropriate energy levels. The use of stable organic materials like TCTA, TAPC, BCP, and TPBi eliminates the need for unstable metal dopants, achieving durable charge generation without the lifetime penalty of doping
4Stability of the object's composition
If there is a difference in LUMO energy level between the P-type charge generation layer and the N-type charge generation layer, then charge distribution is achieved, but electron injection into the N-type charge generation layer deteriorates
Solution Approach 1:
The patent carefully adjusts the LUMO energy level parameter of the P-type CGL and the HOMO energy level parameter of the N-type CGL to create an intermediate energy level梯度的 interface. By selecting P-type materials with LUMO levels of 2.5-3.5 eV and N-type materials with HOMO levels of 5.5-6.0 eV, the patent ensures smooth electron injection while maintaining charge distribution
Solution Approach 2:
The patent introduces an intermediate energy level structure at the interface between the P-type and N-type charge generation layers. The overlapping energy level ranges create a transitional region that facilitates electron injection from the P-type CGL to the N-type CGL, acting as an energy level intermediary that resolves the contradiction between charge distribution and injection efficiency
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 a pyrimidine derivative as an electron transport layer decreases operating voltage, increases emission efficiency, and enhances external quantum efficiency, as demonstrated by comparative examples showing reduced voltage and improved performance metrics.
Implementation Method 1
at least one among the electron transport layers in the at least two light emitting parts includes a compound represented by the following Chemical Formula 1
Implementation Method 2
the difference in LUMO (lowest unoccupied molecular orbital) energy level between the P-type charge generation layer and the N-type charge generation layer deteriorates the property of injecting electrons generated at the interface
Implementation Method 3
the OLED devices are a type of devices that emit light as electrons and holes are paired and extinguished, when a charge is injected into an organic light emitting layer between an anode and a cathode
Implementation Method 4
a second light emitting part using a yellow phosphorescent diode as a light emitting layer. Such a white OLED device produces white light by mixing blue light emitted from the blue fluorescent diode and yellow light emitted from the yellow phosphorescent diode
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An organic light emitting display device is disclosed. The organic light emitting display device comprises at least two light emitting parts (ST1, ST2)between an anode (110) and a cathode (220), each of the light emitting parts having a light emitting layer (140, 190) and an electron transport layer (150, 200), charge generation layers (160N, 160P) between the at least two light emitting parts, wherein at least one among the electron transport layers in the at least two light emitting parts includes a pyrimidine derivative at both sides of the core so as to reduce a driving voltage and increase an efficiency of the organic light emitting display device.