Green OLED Charge Control Layer for Efficiency and Lifespan
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Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face challenges with low luminous efficiency and short luminous lifespan, particularly for green phosphorescent materials, due to the trade-off between efficiency and lifespan, and the increase in thickness leads to higher driving voltage.
Innovation Solution
Incorporating a charge control layer with a second host having a lower LUMO energy level and higher hole mobility than the first host, and a dopant with a maximum luminescence peak in a longer wavelength range, to improve hole transfer and minimize material degradation, thereby enhancing luminous efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the thickness of the emitting material layer including green phosphorescent material is increased to improve luminous lifespan, then luminous lifespan is improved, but driving voltage increases
Solution Approach 1:
A charge control layer is introduced as an intermediary between the emitting material layer and the hole injection layer. This charge control layer includes a second host and a dopant, where the second host has a LUMO energy level lower than the first host and hole mobility three to ten times faster. The charge control layer mediates charge transport, enabling efficient hole injection and transport without requiring increased emitting material layer thickness, thus extending luminous lifespan while maintaining driving voltage at acceptable levels.
2Productivity
If the efficiency of green phosphorescent material is increased to improve luminous efficiency, then luminous efficiency is improved, but luminous lifespan is reduced
Solution Approach 1:
The energy level parameters of the host materials are optimized to resolve the trade-off between luminous efficiency and lifespan. The first host in the emitting material layer and the second host in the charge control layer are selected with specific LUMO energy levels and hole mobilities. The second host has a LUMO energy level lower than the first host and hole mobility three to ten times faster, creating optimal energy level alignment that enables high-efficiency luminescence while reducing material degradation through improved charge transport balance.
3Speed
If a charge control layer with higher hole mobility material is used to improve charge transport, then charge transport is improved, but device complexity increases
Solution Approach 1:
The charge control layer performs multiple functions simultaneously: it serves as a hole transport layer with high hole mobility (three to ten times faster than the first host), acts as an energy level alignment layer with lower LUMO energy level than the first host, and functions as an interface layer between the emitting material layer and the hole injection layer. This multi-functionality enables improved charge transport without proportionally increasing device complexity, as a single layer accomplishes what would otherwise require multiple specialized layers.
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 solution improves luminous efficiency, extends the lifespan of the OLED, and enhances color gamut by minimizing material degradation and maintaining color purity, particularly in green light emission.
Implementation Method 1
the second host has a hole mobility three to ten times faster than a hole mobility of the first host
Implementation Method 2
the second host has a lowest unoccupied molecular orbital (LUMO) energy level lower than a LUMO energy level of the first host
Implementation Method 3
phosphorescent material can show high luminous efficiency since it uses triplet exciton as well as singlet excitons in the luminous process
Implementation Method 4
a dopant that has a maximum luminescence peak in a wavelength range longer than a maximum luminescence peak of the green emitter
Data Source
AI summary
The present disclosure relates to an organic light emitting diode (OLED) and an organic light emitting device having thereof. The OLED includes an emissive layer with at least one emitting part that includes a green emitting material layer including a first host and a green emitter and a charge control layer including a second host and a dopant of which a maximum luminescence wavelength peak range is longer than a maximum luminescence wavelength of the green emitter. The charge control layer enables the OLED to improve its luminous efficiency, extend its color gamut and maximize its luminous lifespan.