OLED Charge Generation Layer Sublayers for Voltage Stability
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Solution Overview
Problem
Existing organic light-emitting diodes (OLEDs), particularly tandem OLEDs with charge generation layers, face challenges in achieving optimal operating voltage, efficiency, and voltage stability.
Innovation Solution
Incorporating a charge generation layer with a n-doped sublayer containing a metal and a n-doped sublayer matrix material comprising phosphine oxide and a heteroaryl group between the emission layers, and using a non-emissive electron transport layer adjacent to the n-doped sublayer without n-dopants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional charge generation layers are used in tandem OLEDs, then the device structure is established, but the operating voltage remains high and efficiency is insufficient
Solution Approach 1:
The charge generation layer is divided into functionally distinct sublayers: a p-doped sublayer adjacent to the first emission layer and an n-doped sublayer adjacent to the second emission layer. Each sublayer has localized doping characteristics optimized for its specific function, enabling balanced charge generation and transport while reducing operating voltage and improving efficiency.
Solution Approach 2:
The charge generation layer employs composite material structures combining different dopants (p-type and n-type) with appropriate matrix materials in each sublayer. This composite approach enables simultaneous optimization of hole injection from the first emission layer and electron injection from the second emission layer, resolving the contradiction between operating voltage and efficiency.
2Reliability
If charge generation layers are implemented in tandem OLEDs, then charge injection is enabled, but voltage stability deteriorates
Solution Approach 1:
The charge generation layer is segmented into p-doped and n-doped sublayers, each responsible for specific charge injection functions. This segmentation enables independent optimization of hole and electron injection characteristics, achieving balanced charge injection that stabilizes operating voltage over time.
Solution Approach 2:
The doping levels, material compositions, and thickness parameters of the p-doped and n-doped sublayers are specifically adjusted to achieve optimal charge balance. By changing these parameters, the device achieves stable voltage characteristics while maintaining efficient charge injection into both emission 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
This configuration reduces operating voltage and improves efficiency and voltage stability in OLEDs by balanced charge injection and transport.
Implementation Method 1
the n-doped sublayer provides electrons to the light emission layer arranged closer to the anode
Implementation Method 2
the p-doped sublayer provides holes to the light emission layer arranged near the cathode
Implementation Method 3
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted.
Data Source
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AI summary
The present invention relates to an organic light emitting device, a display device comprising the same and to a compound.