OVJP Nozzle Throttle Design for Shock Front Dissipation
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Solution Overview
Problem
In organic vapor jet printing (OVJP), sudden pressure drops at the nozzle outlet cause shock fronts, leading to increased overspray and divergence of the molecular beam, which results in inconsistent deposition patterns and reduced resolution.
Innovation Solution
Designing nozzles with a throttle portion between the inlet and outlet, where the cross-sectional area ratio (A1/A2) is greater than 16, and the distance (L1) between the throttle and outlet allows for the formation and dissipation of shock fronts before the vapor exits, creating a collimated jet and minimizing overspray.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional nozzle design is used in OVJP, then the device complexity is low, but sudden pressure drops at the nozzle outlet cause shock fronts leading to increased overspray and reduced manufacturing precision
Solution Approach 1:
The nozzle is segmented into multiple functional sections: a body portion, a throat portion with reduced cross-sectional area, and an outlet portion. This segmentation allows the shock front to form and dissipate within the throat section before vapor exits, preventing beam divergence and reducing overspray while maintaining controlled deposition patterns.
Solution Approach 2:
The throat portion acts as an intermediary section between the body and outlet of the nozzle. It provides a transition zone where the vapor flow can adjust to pressure changes, allowing shock fronts to form and dissipate in a controlled manner before the vapor reaches the outlet, thereby preventing sudden pressure drops that cause beam divergence.
2Manufacturing precision
If the nozzle outlet cross-sectional area is reduced to improve resolution, then the deposition precision improves, but the vapor flow velocity increases causing shock fronts and increased overspray
Solution Approach 1:
The nozzle is divided into sections with different cross-sectional areas. The throat portion has a reduced area that increases vapor velocity and forms shock fronts, while the outlet portion has a larger area that allows controlled expansion. This segmentation enables resolution improvement through precise outlet sizing while managing velocity effects through the intermediate throat section.
Solution Approach 2:
The throat portion serves as an intermediary that mediates between the vapor source and the outlet. It provides a transition zone where velocity increases and shock fronts form in a controlled manner, preventing direct sudden expansion at the outlet that would cause beam divergence and overspray.
3Ease of manufacture
If the nozzle structure is simplified to reduce device complexity, then the ease of manufacture improves, but shock fronts form at the outlet causing beam divergence and reduced manufacturing precision
Solution Approach 1:
The nozzle is segmented into manufacturable sections (body, throat, outlet) with distinct geometric features. Each section can be fabricated and assembled separately, maintaining the complex internal flow dynamics needed for shock front control while allowing for practical manufacturing processes.
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 configuration significantly reduces overspray and enhances the consistency and resolution of the deposited organic material patterns, ensuring that the width of the deposited material matches the nozzle outlet, thereby improving the accuracy of organic opto-electronic devices like OLEDs.
Implementation Method 1
sudden pressure drops at the end of the nozzle close to the substrate may create a shock front, which may cause the molecular beam to diverge out from the nozzle and increase overspray
Implementation Method 2
the distance (L1) between the throttle and outlet allows for the formation and dissipation of shock fronts before the vapor exits, creating a collimated jet and minimizing overspray
Data Source
AI summary
Nozzle designs which have been found to be effective in governing overspray in OVJP are provided. Aspects of the invention have been found to be effective in reducing or avoiding sudden pressure drops at the end of the nozzle close to the substrate, and may be advantageously employed in obtaining, for example, greater consistency between the nozzle outlet diameter and the deposited pattern width.