Microcavity Pixel Array With Intermediate Electrode Cavity Tuning
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Solution Overview
Problem
Current microcavity OLED designs for light-field displays face challenges in achieving high angular resolution and wide field of view due to limitations in controlling spectral bandwidth and output angle, particularly in material and thickness constraints of filler layers, which affect color tuning and optical path length optimization.
Innovation Solution
Incorporating an intermediate electrode with an overhang region to connect with the bottom electrode, allowing for flexible material selection and thickness adjustments, and using blanket deposition methods for select layers to tune the optical cavity length, thereby alleviating electron-hole balancing requirements and enabling multi-colored microcavity pixel arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional two electrode microcavity OLED design is used, then the structure is simple, but the material and thickness choices are constrained by electron-hole balancing requirements, limiting color tuning flexibility
Solution Approach 1:
The device is segmented into three electrode layers: bottom electrode, intermediate electrode, and top electrode. This segmentation allows the intermediate electrode to serve dual purposes: electrical conduction and optical cavity tuning, while the top electrode can be optimized purely for optical reflection without electron-hole balancing constraints.
Solution Approach 2:
An intermediate electrode layer is introduced as a mediator between the bottom and top electrodes. This intermediate layer provides the flexibility to adjust optical cavity parameters (thickness, material composition) independently of electrical charge balance requirements, as it can be compensated by adjustments in the organic stack or other electrodes.
2Adaptability or versatility
If a filler layer is added to adjust microcavity optical path length, then color tuning is improved, but the filler layer thickness and material choices are constrained by conductivity requirements
Solution Approach 1:
The intermediate electrode acts as an intermediary layer that can be optimized for optical properties without strict conductivity requirements. By distributing the electrical function across three electrodes, the intermediate layer can use materials with lower conductivity or even insulating materials, expanding material selection freedom for optical tuning.
Solution Approach 2:
The patent changes the electrical architecture parameter from two electrodes to three electrodes, which fundamentally alters the constraints on filler/intermediate layer materials. This parameter change allows the intermediate layer to prioritize optical properties (refractive index, thickness) over electrical conductivity.
3Ease of operation
If a thicker TCO filler layer is used to adjust cavity length, then optical path length control is improved, but light absorption loss increases
Solution Approach 1:
The intermediate electrode serves as a mediator that can provide optical path length adjustment without the light absorption problems of thick TCO layers. By using materials with lower absorption coefficients (such as metal oxides, organic dielectrics, or even air gaps) in the intermediate electrode, the patent achieves cavity tuning with minimal energy loss.
Solution Approach 2:
The patent replaces expensive and lossy thick TCO filler layers with alternative materials that achieve the same optical tuning function with lower absorption. This substitution uses materials that are either naturally lower-loss or can be applied as thin films, effectively replacing the 'expensive' thick TCO approach.
4Manufacturing precision
If different thicknesses are required for R, G, B colors in microcavity OLED, then color accuracy is improved, but additional patterning steps are required after OLED patterning
Solution Approach 1:
The intermediate electrode is deposited before the OLED organic stack, allowing its thickness to be pre-adjusted for each color region. This preliminary action enables color-specific optical cavity tuning to be built into the structure before organic layer deposition, avoiding post-OLED patterning steps.
Solution Approach 2:
The patent moves the color tuning adjustment from the organic stack dimension to the electrode dimension (specifically the intermediate electrode). By adjusting intermediate electrode thickness in the vertical dimension before organic deposition, the patent achieves color accuracy without requiring complex lateral patterning after OLED fabrication.
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 approach enhances material and thickness flexibility, allowing for optimized optical path length adjustments without impacting charge balance, resulting in improved spectral bandwidth control and output angle performance for multi-colored microcavity OLEDs.
Implementation Method 1
an intermediate electrode on top of the filler layer comprising an overhang region and a connecting area, the connecting area electrically connecting the intermediate electrode to the bottom first electrode
Implementation Method 2
The wavelength of the light output by such a resonant OLED structure is dependent, in part, upon this optical path length of the microcavity
Implementation Method 3
Light is generated in an OLED device when electrons and holes that are injected from the cathode and the anode (electrodes), respectively, flow through the ETL and the HTL and recombine in the EML
Implementation Method 4
A DBR is an optical mirror composed of multiple pairs of two different dielectric layers with different refractive indices in an alternating order. The highest reflectivity is attained when the layer thicknesses are chosen such that the optical path length of each layer is one quarter of the resonance wavelength
Implementation Method 5
The first mirror can be a metal cathode and the second mirror may be a layered stack of non-absorbing materials
Data Source
AI summary
A microcavity pixel design and structure allowing for tuning the optical cavity length of the microcavity of a microcavity pixel structure. This is achieved by including an intermediate electrode in the device which has an overhang region to form a connecting area to a bottom electrode, alleviating design restrictions in material type and dimensions throughout the optical microcavity tuning process. A method for the fabrication of a multi-colored microcavity pixel array facilitating the use of blanket deposition methods for select layers within a microcavity pixel structure.