Alternating Host-Dopant Sub-Layers for OLED Conductivity
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Solution Overview
Problem
Current methods for producing electrically doped layers in electronic devices, such as PIN OLEDs, face challenges in achieving high electrical conductivity due to low vapour pressure and limited interaction between host and dopant materials during deposition, leading to reduced conductivity in doped layers.
Innovation Solution
The method involves alternating deposition of host and dopant materials as non-mixed sub-layers, allowing for a chemical redox reaction at interfaces to create a composite layer structure with enhanced charge transfer, using techniques like Vacuum Thermal Evaporation (VTE) and Organic Vapour Phase Deposition (OVPD), with precise control over layer thickness and molar ratios to achieve higher conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If host and dopant materials are evaporated simultaneously in different crucibles using VTE, then electrical doping can be achieved, but the low vapour pressure and long mean free path prevent effective mixing and chemical reactions in the gas phase, resulting in reduced conductivity
Solution Approach 1:
The patent segments the doped layer into alternating sub-layers of host material and dopant material, each deposited separately. This segmentation ensures proper mixing and chemical reactions at interfaces while avoiding gas-phase mixing issues, achieving both reliable conductivity and ease of manufacture through controlled sequential deposition.
Solution Approach 2:
The patent applies preliminary action by pre-depositing host material sub-layers before dopant material sub-layers in alternating sequences. This preliminary arrangement of host layers creates ready interfaces for subsequent dopant deposition, ensuring effective mixing and chemical reactions occur at predetermined locations, thereby improving conductivity without gas-phase mixing complications.
2Productivity
If the deposition rate is increased to high throughput (up to 5nm/s), then productivity improves, but the low vapour pressure conditions and short shared path of host and dopant molecules reduce mixing efficiency and chemical reaction completeness
Solution Approach 1:
The patent segments the deposition process into alternating cycles of host material deposition and dopant material deposition. Each cycle deposits thin sub-layers sequentially, ensuring complete mixing and chemical reactions at interfaces even at high deposition rates. This segmentation maintains doping concentration uniformity while achieving high throughput production.
Solution Approach 2:
The patent employs periodic action by alternating between host material deposition and dopant material deposition in repeated cycles. This periodic deposition pattern ensures consistent mixing and chemical reactions occur at each interface cycle, maintaining uniform doping concentration across the layer while enabling high productivity through continuous cyclic operation.
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 results in improved electrical conductivity, with conductivity values up to 10^-5 S/cm, surpassing non-doped host material conductivity, and allows for more efficient production of electrically doped layers with uniform thickness and smooth layer structures.
Implementation Method 1
a redox reaction occurs between host and dopant molecules and results in an at least partial charge transfer, thereby providing additional free charge carriers which increase the electrical conductivity
Implementation Method 2
The materials are thermally evaporated from independent crucibles. Temperature is chosen to meet the evaporation point of the material at high vacuum conditions
Implementation Method 3
The OVPD process is based on the sublimation of small molecular weight organic materials into an inert carrier gas stream in a hot walled chamber
Implementation Method 4
The gas transports the molecules to a cooled substrate where they rapidly condense to form the desired film
Data Source
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AI summary
The invention relates to a method for producing a layer structure in an electronic device, especially in an organic light emitting device, the method comprising a step of producing the layer structure as a composite layer structure with free charge carriers generated by charge transfer between a first material and a second material, wherein the composite layer structure is provided as a stack of at least three non-mixed sub-layers made of the first material and the second material, respectively, wherein within the stack of the at least three non-mixed sub-layers each first material sub-layer is followed by an adjacent second material sub-layer and each second material sub-layer is followed by an adjacent first material sub-layer, and wherein the first material and the second material are selected to form a host-dopant material system for the electrical doping. The invention also relates to an electronic device.