Insoluble Charge Transporting Layer for Solution-Processed OLEDs
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Solution Overview
Problem
Existing organic light-emitting diodes (OLEDs) face challenges in forming multiple layers via solution deposition due to solubility issues, where initially deposited layers often dissolve in solvents used for subsequent layers, limiting the selection of materials and requiring complex processes like thermal conversion with corrosive by-products.
Innovation Solution
A method is developed to render a charge transporting layer insoluble by treatment, such as heat or electromagnetic radiation, allowing for the formation of a phosphorescent OLED with multiple solution-processable layers, including a hole transporting layer and an electroluminescent layer, using a polymer with a triarylamine repeat unit and a metal complex phosphorescent material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solution deposition is used to form multiple layers, then processing is simplified, but initially deposited layers dissolve in solvents used for succeeding layers
Solution Approach 1:
The patent applies preliminary action by treating the first deposited layer (hole transporting layer) with a solubilizing agent before depositing the second layer. This preliminary treatment modifies the solubility characteristics of the first layer, preventing it from dissolving when the second layer is subsequently deposited from solution, thus enabling multi-layer solution processing without layer dissolution issues
Solution Approach 2:
The patent changes the solubility parameter of the hole transporting layer by treating it with a solubilizing agent. This parameter change transforms the layer from a soluble state (which would dissolve in subsequent solvents) to an insoluble or reduced-solubility state, allowing stable multi-layer formation through solution deposition
2Stability of the object's composition
If thermal conversion is used to form insoluble layers, then layer stability is improved, but corrosive by-products are generated
Solution Approach 1:
The patent substitutes the thermal conversion process (which uses heat to induce chemical changes) with a chemical treatment process using solubilizing agents. This replacement eliminates the need for high-temperature processing and avoids generation of corrosive by-products, while still achieving the desired insolubility of the hole transporting layer
Solution Approach 2:
Instead of using thermal conversion that generates harmful corrosive by-products, the patent employs a chemical treatment approach where the solubilizing agent selectively modifies the hole transporting layer. This converts a potentially harmful process into a beneficial one, achieving layer stabilization without environmental or device damage
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 enables the formation of efficient phosphorescent OLEDs with improved quantum efficiency and extended lifetime by preventing layer dissolution and minimizing corrosive by-products, while allowing for the use of a wider range of materials in solution processing.
Implementation Method 1
treatment of the charge transporting layer to render it insoluble in the solvent
Implementation Method 2
utilizing spin-orbit coupling effects in metal complexes that enable triplet excitons to undergo radiative decay
Implementation Method 3
The holes and electrons combine in the organic electroluminescent layer to form an exciton which then undergoes radiative decay to give light
Data Source
AI summary
A method of forming an organic light emitting diode comprising the steps of: providing a substrate comprising a first electrode for injection of charge carriers of a first type; forming a charge transporting layer by depositing over the substrate a charge transporting material for transporting charge carriers of the first type, the charge transporting material being soluble in a solvent; treating the charge transporting layer to render it insoluble in the solvent; forming an electroluminescent layer by depositing onto the charge transporting layer a composition comprising the solvent, a phosphorescent material, and a host material; and depositing over the electroluminescent layer a second electrode for injection of charge carriers of a second type.