QLED Function Layer Viscosity Tuning for Slit Coating
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Solution Overview
Problem
The viscosity of solvents used in quantum dot light-emitting diode (QLED) manufacturing is often too low, limiting the application methods for film formation, particularly in the case of quantum dot light-emitting diodes where the selection of ligands and solvents is critical.
Innovation Solution
Incorporating nanofibers into the solvent solutions for the charge transport and light-emitting layers, which adjusts the viscosity to an optimal range, enabling the use of slit coating methods and subsequent photolithography for pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a solvent with low viscosity is used for quantum dot dispersion, then the quantum dots can be well dispersed, but the application method for film formation is limited
Solution Approach 1:
The patent uses a composite material consisting of a nanofiber network formed from a water-soluble polymer and metal salts. This composite structure provides both the dispersion stability needed for quantum dots and the viscosity necessary for slit coating application, resolving the contradiction between good dispersion and manufacturable film formation
Solution Approach 2:
The patent changes the viscosity parameter of the solvent system by introducing a water-soluble polymer that forms a nanofiber network. This parameter change enables the transition from a low-viscosity solvent (limiting application methods) to a higher-viscosity composite solution suitable for slit coating, while maintaining quantum dot dispersion stability
2Ease of manufacture
If nanofibers are incorporated into the solvent solution, then the viscosity is adjusted to an optimal range for slit coating, but the solution composition becomes more complex
Solution Approach 1:
The patent uses a water-soluble polymer with specific molecular weight and functional groups that self-assemble into nanofibers through hydrogen bonding and hydrophobic interactions. By controlling the polymer concentration and molecular weight, the viscosity is tuned to the optimal range for slit coating without requiring complex formulation
3Manufacturing precision
If photolithography is performed on the applied layer, then uniform pattern formation is achieved, but cracking may occur in the film
Solution Approach 1:
The patent introduces a plasticizer into the water-soluble polymer matrix to locally enhance the flexibility and crack resistance of the film in regions subjected to photolithography processing. This local quality enhancement maintains film integrity during patterning while allowing precise pattern formation
Solution Approach 2:
The patent incorporates a plasticizer and optimizes the polymer composition beforehand to prevent cracking during subsequent photolithography. This prior cushioning approach ensures the film has sufficient flexibility to withstand the drying and processing stresses without compromising pattern precision
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 allows for the successful application and patterning of layers with uniform thickness and suppressed cracking, enhancing the light-emission characteristics of quantum dot-based display devices.
Implementation Method 1
Incorporating nanofibers into the solvent solutions for the charge transport and light-emitting layers, which adjusts the viscosity to an optimal range
Implementation Method 2
performing photolithography on a layer formed as a film by the applied solution to form a function layer including the light-emitting material or the charge transport material
Data Source
AI summary
A display device includes a first electrode, a second electrode, a light-emitting layer provided between the first electrode and the second electrode, and a charge transport layer provided between the first electrode and the second electrode and containing a charge transport material configured to transport a charge to the light-emitting layer. At least one layer of the light-emitting layer and the charge transport layer is a function layer including a nanofiber and a photosensitive material.