Yohan Kim | Fraunhofer IAP: Is Electrohydrodynamic Jetting the Key to Printing 2000+ PPI MicroLED Displays?
00:13:48 - 00:16:01
Other snippets from this talk
Summary of the clip:
Is Electrohydrodynamic Jetting the Key to Printing 2000+ PPI MicroLED Displays?
Yohan Kim introduces Electrohydrodynamic (EHD) jet printing as a revolutionary replacement for traditional inkjet printing in near-eye AR/VR microdisplays. While standard inkjet nozzle mechanics fail to scale beyond 500 PPI, EHD jetting utilizes electrostatic forces to create a Taylor cone, yielding jet diameters up to five orders of magnitude smaller than the physical nozzle.
A critical challenge in executing EHD printing with QD inks is controlling the charge density of the colloidal suspension within the high-intensity electric field. The researchers discovered that modifying the QD surface chemistry with chloride ligands dramatically optimizes the negative zeta potential.
This surface treatment reduces the threshold voltage required for stable Taylor cone formation. This breakthrough enables highly precise, sub-micron patterning of red and green QD pixels inside micro-bank structures, paving the way for displays exceeding 2,000 PPI.
In this short video, you can learn:
* How EHD jetting utilizes electrostatic Taylor cones to print sub-micron QD features far below physical nozzle diameters
* The role of chloride surface ligands in optimizing QD charge density and reducing cone-forming voltage
* Why high-resolution additive manufacturing is essential for AR/VR displays requiring over 2,000 PPI
š **Clip Abstract** Yohan Kim explains the physics of Electrohydrodynamic (EHD) jeting for printing sub-micron quantum dot patterns for ultra-high density microdisplays. By modifying the QD surface with chloride ligands, the team optimized charge density and zeta potential, lowering the threshold voltage required for ultra-fine printing.
š Link in comments š
#ElectrohydrodynamicJetting, #QuantumDotInks, #ChlorideLigands, #TaylorCone, #MicroLEDDisplays, #NearEyeMicrodisplays
This is a highlight of the presentation:
More Highlights from the same talk.
00:04:33 - 00:06:55
Can Quantum Dots Solve the MicroLED "Green Gap" and Angular Color Shift Challenges?
Can Quantum Dots Solve the MicroLED "Green Gap" and Angular Color Shift Challenges?
In this segment, Yohan Kim discusses the integration of Quantum Dots (QDs) with blue MicroLEDs to overcome the notorious "green gap" and efficiency drops in sub-10 micrometer red chips. He outlines how different active materials yield varying angular emission intensities, causing pronounced color shifts at wider viewing angles and higher drive currents.
By utilizing a monolithic blue MicroLED array coupled with printed red and green QD color conversion layers, developers can significantly simplify the display backplane architecture. This hybrid approach eliminates the driving voltage disparities of individual RGB LED materials, drastically cutting backplane design complexity and manufacturing costs.
The discussion underscores why QD color conversion is becoming a leading strategy for high-performance AR/VR microdisplays, enabling high color uniformity and luminance stability without sacrificing the raw efficiency of blue gallium nitride (GaN) emitters.
In this short video, you can learn:
* Why sub-10Āµm red and green microLEDs suffer from severe efficiency losses and color shifting
* How combining QD color conversion with a single-color blue GaN microLED array simplifies backplane driver design
* The commercial advantages of reducing driving voltage variations across the display backplane
š **Clip Abstract** Yohan Kim analyzes the physical and electrical bottlenecks of native RGB MicroLED arrays, particularly the green gap and efficiency loss in ultra-small red chips. He proposes a hybrid architecture utilizing blue GaN microLEDs and printed QD color converters to reduce angular color shift and simplify backplane driver integration.
š Link in comments š
#QuantumDotColorConversion, #MicroLED, #BlueGaN, #AngularColorShift, #ARVRMicrodisplays, #PrintedElectronics
00:08:50 - 00:10:41
How Can Shell Engineering Stop Blue Light Leakage in Cadmium-Free Quantum Dots?
How Can Shell Engineering Stop Blue Light Leakage in Cadmium-Free Quantum Dots?
In this clip, the technical challenges of cadmium-free Indium Phosphide (InP) quantum dots are analyzed, specifically their lower absorption cross-section compared to cadmium-based alternatives. This difference leads to a "blue valley" near 450 nm in the absorption spectrum, causing unacceptable blue light leakage in green QD color filters.
To mitigate this leakage without resorting to complex external distributed Bragg reflectors (DBRs) or thick color-purifying layers, researchers engineered the intermediate shell structure of the InP nanoparticles. By tuning the gradient shell, they succeeded in increasing the absorption index (gamma value) from 0.8 to 1.9.
This material-level optimization directly improves the external quantum efficiency (EQE) and color conversion efficiency of cadmium-free green quantum dots. It offers display manufacturers a cleaner, more cost-effective pathway to meeting BT.2020 color volume standards.
In this short video, you can learn:
* The optical absorption deficiencies of cadmium-free InP quantum dots compared to CdSe-based options
* How intermediate shell engineering increases the blue light absorption index (gamma value) from 0.8 to 1.9
* Why solving the 450nm absorption valley at the material level is superior to using external Bragg reflectors
š **Clip Abstract** This clip details how engineering the intermediate shell structure of indium phosphide (InP) quantum dots can resolve the blue light leakage typical of green cadmium-free formulations. By increasing the 450nm absorption index, researchers enhanced conversion efficiency and eliminated the need for costly color-filtering layers.
š Link in comments š
#InPQuantumDots, #ShellEngineering, #BlueLightLeakage, #QDColorFilters, #BT2020, #QuantumDotDisplays