Keeping MicroLEDs Dry: Advances in Moisture Resistance Protecting Next-Gen Displays

Protecting sensitive microLED devices from moisture damage is critical for enabling their reliability in real-world operating conditions. From wearable electronics to vehicle cockpits and even outdoor video billboards, these emerging self-emissive displays face exposure to humidity, rain, splashes and more.

Fortunately, recent innovations in multilayer encapsulation barriers, engineered hydrophobic surfaces, and integrated blocking layers aim to substantially improve microLED water resistance for diverse applications.

But what are the key technologies ensuring next-generation microLED reliability? Here we explore promising techniques to repel water while locking out moisture.

Innovations to Repel, Block, and Resist Moisture Damage in microLEDs

MicroLEDs stand to revolutionize displays with their high brightness, response times, reliability and efficiency. However, being semiconductor-based, they remain vulnerable to corrosion and electrical leakage when exposed to moisture like any electronics.

While thorough sealing can protect devices, complete isolation is often impractical, especially in flexible displays. This drives research into alternative moisture defense strategies for robust, long-duration microLED operation.

1. Multilayer Encapsulation Barriers

Novel combinations of protective encapsulant materials and specialized deposition processes enable robust blocking of moisture permeation into microLED devices.

ALD Nanolaminates

Atomic layer deposition (ALD) allows depositing conformal nanometer-thick layers of aluminum oxide that effectively impede moisture diffusion through their amorphous structure. ALD enables encapsulation both underneath and on top of the LED array.

Flexible Polymer Encapsulants

Soft polymer coatings up to several millimeters thick allow some flexing and impact cushioning of thin flexible displays. Carefully engineered polymers provide a moisture permeation barrier over the lifetime of devices.

Glass-Polymer Hybrid Caps

Monolithic glass capping layers ensure the highest barrier performance while integrated thin polymer layers help relieve stresses from differential thermal expansion, preventing fracturing and cracking over repeated thermal cycles.

2. Engineered Hydrophobic Surfaces

While blocking moisture permeation is ideal, alternative emerging approaches focus on using nanostructured hydrophobic coatings around microLEDs to prevent wetting, condensation formation, and wicking of surface water into the devices.

Molecular Fluorosilane Monolayers

Densely grafted single layers of fluorinated silane molecules covalently attached to surfaces create hydrophobic interfaces that water beads up on. This prevents wetting of the LED metallization and driving electronics.

Liquid-Infused Porous Polymer Films

Micro-nanostructured porous polymer coatings can be infused with immobilized water-repellent oils that maintain hydrophobicity even after surface abrasion. These self-healing liquid layers prevent wetting of underlying device layers.

Carbon Nanotube Arrays

Dense non-wetting carpets of vertically aligned carbon nanotubes effectively repel water droplets while physically shielding the surfaces they are grown on. Carbon nanotube “forests” provide hydrophobic protection without affecting light emission.

3. Integrated Blocking Layers

Finally, emerging approaches focus on building in nanoscale moisture barriers directly into microLED structures to prevent and block infiltrating water molecules from reaching vulnerable layers.

Desiccant Nanoparticle Inks

Porous hygroscopic metal oxide nanoparticles printed between device layers act as desiccants that absorb trace moisture. Careful nanoparticle sizing prevents light scattering while durably eliminating moisture.

ALD Diffusion Barriers

Encapsulating moisture-blocking metals like aluminum with conformal nanolaminates of aluminum oxide deposited by ALD provides ultrathin, defect-free diffusion barriers throughout the device structure.

Flexible Calcium Oxide Layers

Thin reactive calcium oxide films fabricated between device layers absorb moisture through oxidation reactions. The hydrophilic films capture infiltrating water molecules before they can reach electrodes.

In summary, multilayer encapsulation, surface engineering for hydrophobicity, and embedded moisture capture layers all offer promising ways to defend sensitive microLEDs against damaging water ingress and humidity.

As these technologies mature, they will enable microLED adoption across a widening range of moisture-facing applications from smart watches to automotive displays, unlocking the technology’s tremendous potential beyond conventional screened devices.