Organic Electroluminescent Element with Mesoporous Silica Emitting Layer
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Solution Overview
Problem
Conventional organic electroluminescent elements suffer from reduced light extraction efficiency due to light being totally reflected at interfaces, primarily because the refractive index of the emitting layer is too high, leading to confined light and reduced external quantum efficiency.
Innovation Solution
Incorporating mesoporous silica nanoparticles with a low refractive index into the emitting layer, featuring a chain hydrocarbon structure and π-conjugated organic functional groups on their surface, to lower the refractive index of the emitting layer and widen critical angles, thereby enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the emitting layer uses conventional organic materials with high refractive index, then the layer can be formed with standard materials, but light extraction efficiency is reduced due to total internal reflection at interfaces
Solution Approach 1:
The emitting layer is formed as a composite material combining conventional organic light-emitting materials with microporous silica particles. This composite structure allows the layer to maintain ease of formation through standard coating processes while the microporous silica particles create an effective low refractive index environment that reduces total internal reflection and improves light extraction efficiency
Solution Approach 2:
Microporous silica particles are incorporated into the emitting layer to create a porous composite structure. The micropores within the silica particles contribute to lowering the effective refractive index of the emitting layer, thereby reducing optical confinement and improving light extraction without complicating the manufacturing 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
The use of mesoporous silica nanoparticles in the emitting layer reduces light loss at interfaces, significantly improving light extraction efficiency and external quantum efficiency by allowing more photons to be emitted to the atmosphere.
Implementation Method 1
When light propagates from a medium with a high refractive index to a medium with a low refractive index, a critical angle at an interface therebetween is determined based on the refractive index between the media in accordance with Snell's law
Implementation Method 2
light which has a higher incident angle than the critical angle is totally reflected at the interface, confined to the medium with the high refractive index, and lost as guided light
Implementation Method 3
When a voltage is applied, the anode 11 injects holes into the emitting layer 13 and the cathode 15 injects electrons into the emitting layer 13, and the holes and the electrons are recombined in the emitting layer 13. This recombination causes excitons to be generated, and when the excitons return to their ground state, photons are emitted
Data Source
Figure 1~2
Figure 3~4
AI summary
In an organic electroluminescent element, light extraction efficiency is enhanced. An organic electroluminescent element 1 is configured by laminating a substrate 2, a first electrode 3, an organic layer 4, and a second electrode 5 in this order. The organic layer 4 includes an emitting layer 43, and the emitting layer 43 is formed by mixing porous particles 45 into an emitting material 44.