OLED Emitter Layer Exciton Trap Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current organic light-emitting diodes (OLEDs) face inefficiencies due to charge carrier trapping and reduced mobility, leading to increased operating voltage and reduced power efficiency, especially when using high concentrations of emitter materials with high photoluminescence efficiency.
Innovation Solution
Incorporating a phosphorescent exciton trap in the emitter layer with a higher weight fraction than the radiation-emitting emitter, where the emission maximum of the exciton trap is at a shorter wavelength, improves charge carrier balance and efficiency by facilitating better charge carrier transport and energy transfer to the emitter material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high concentrations of emitter materials are used to improve photoluminescence efficiency, then quantum efficiency increases, but charge carrier mobility decreases and operating voltage increases
Solution Approach 1:
The patent introduces an exciton trap as an intermediary substance that mediates between the emitter molecules and charge carriers. The exciton trap accepts excitons from the matrix and transfers them to the emitter, enabling efficient energy transfer while keeping emitter concentration low. This resolves the contradiction by allowing high quantum efficiency through the exciton trap-emitter interface without requiring high emitter concentrations that would reduce charge carrier mobility
Solution Approach 2:
The patent changes the concentration parameter of the emitter material from high to low (0.5-5 wt%), and compensates for the reduced direct emitter-matrix interactions by introducing the exciton trap at higher concentrations (5-30 wt%). This parameter change allows maintaining high quantum efficiency through the exciton trap while preserving charge carrier mobility in the matrix
2Illumination intensity
If high concentrations of emitter materials are used, then more light is emitted, but charge carriers are trapped and operating voltage increases
Solution Approach 1:
The exciton trap serves as a mediator that separates the functions of light emission and charge carrier transport. By concentrating the emission function in the trap-emitter interface and keeping emitter concentration low, charge carriers can move freely through the matrix without being trapped, thus maintaining low operating voltage while still achieving high light output through efficient exciton-to-emitter energy transfer
3Productivity
If emitter concentration is increased to improve efficiency, then more excitons are generated, but charge carrier balance deteriorates
Solution Approach 1:
The exciton trap acts as an intermediary that decouples exciton generation from emitter concentration. Excitons are generated in the matrix and transferred to the exciton trap, which then transfers them to the low-concentration emitter. This maintains good charge carrier balance in the matrix while still achieving high exciton generation and light output through the trap-mediated process
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 enhances current and power efficiency by at least 10% and up to 25% at luminances of 10 to 1100 cd/m², with improved external quantum efficiency and reduced operating voltage, while maintaining a similar color impression and exciton lifespan.
Implementation Method 1
the matrix transports the majority charge carriers and the exciton trapper transports the minority charge carriers
Implementation Method 2
energy transfer to the emitter material
Data Source
Figure 1
Figure 2~3
Figure 4~5a
AI summary
The invention relates to a radiation emitting device comprising a substrate, a first and a second electrode, and an emitter layer that is placed between the first and the second electrode. The emitter layer contains a matrix material, 0.5 to 5 percent by weight of a radiation emitter, and 5 to 30 percent by weight of a phosphorescent exciton trap. The weight ratio of the exciton trap is greater than that of the radiation emitter, and the maximum emission of the exciton trap lies at a shorter wavelength than that of the radiation emitter. Furthermore, the radiation emitting device is characterized in that the current efficiency of the emitter layer is at least 10 percent greater than the current efficiency of an emitter layer without an exciton trap.