Stacked OLED Host-Dopant Architecture for Voltage and Lifespan
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Solution Overview
Problem
Conventional organic light-emitting devices face challenges in achieving low driving voltage and high efficiency while maintaining balanced luminescence efficiency and lifespan.
Innovation Solution
The organic light-emitting device incorporates multiple light-emitting units with specific emission layers and charge generation layers, including a first emission layer with a hole transport compound and a second emission layer with an electron transport compound, along with phosphorescent and fluorescent dopants, to optimize hole and electron mobility and luminescence efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple light-emitting units are stacked in series to achieve high efficiency and desired characteristics, then luminance and response speed improve, but device complexity increases
Solution Approach 1:
The device is divided into multiple light-emitting units (first, second, third light-emitting units) with distinct emission layers and charge generation layers. Each unit contains specific host compounds and dopants optimized for its function, allowing independent optimization of luminescence efficiency while maintaining modular structure for manageable complexity
Solution Approach 2:
Different regions of the device have specialized compositions: the first emission layer uses a first host compound with first and second dopants for high luminescence efficiency, the second emission layer uses a second host compound with third and fourth dopants for complementary characteristics, and charge generation layers use specific compounds for efficient charge carrier generation. This local optimization resolves the contradiction by allowing each segment to be tuned for its specific function
2Productivity
If phosphorescent dopants are used in emission layers to enhance luminescence efficiency, then luminance improves, but lifespan decreases due to triplet state accumulation
Solution Approach 1:
The device merges phosphorescent dopants (first dopant in first emission layer, third dopant in second emission layer) with fluorescent dopants (second dopant in first emission layer, fourth dopant in second emission layer) within the same emission layers. This combination allows simultaneous exploitation of phosphorescent high efficiency and fluorescent long lifespan characteristics, resolving the contradiction between luminescence efficiency and device lifespan
Solution Approach 2:
The emission layers are formulated as composite materials containing multiple host compounds and multiple dopant types. The first emission layer comprises a first host compound, a second host compound, a phosphorescent dopant, and a fluorescent dopant. This composite approach enables synergistic effects where phosphorescent materials provide high efficiency while fluorescent materials extend operational lifetime
3Use of energy by moving object
If electron transport compounds are used as hosts in emission layers to improve electron mobility, then driving voltage reduces, but hole transport capability deteriorates
Solution Approach 1:
The host compounds in the emission layers are designed with multi-functional characteristics. The first host compound and second host compound in the first emission layer, along with the third host compound and fourth host compound in the second emission layer, are selected to provide both electron transport and hole transport capabilities. This multi-functionality allows the host materials to simultaneously improve electron mobility (reducing driving voltage) while maintaining adequate hole transport (ensuring charge balance), thus resolving the contradiction
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 reduces driving voltage, enhances luminescence efficiency, and improves lifespan by balancing hole and electron mobility, resulting in improved emission characteristics.
Implementation Method 1
Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transition from an excited state to a ground state to thereby generate light.
Implementation Method 2
the first dopant may be a phosphorescent dopant
Implementation Method 3
the second dopant may be a fluorescent dopant
Data Source
AI summary
Embodiments provide an organic light-emitting device and an electronic apparatus including the organic light-emitting device. The organic light-emitting device includes a first electrode, a second electrode facing the first electrode, m light-emitting units stacked between the first electrode and the second electrode and each including an emission layer, and m−1 charge generation layers between adjacent ones of the m light-emitting units, wherein m is an integer of 2 or more, at least one of the emission layers of the light-emitting units includes a first emission layer and a second emission layer, the first emission layer includes a first host, a second host, a first dopant, and a second dopant, the second emission layer includes a third host and a third dopant.