Once considered a mere alternative, copper is now paving the way for a new generation of high-performance, sustainable displays.
The evolution of display technology has long been constrained by a fundamental problem: the best-performing materials tend to be among the rarest elements on Earth.
Iridium, used in many high-end OLED displays, has an abundance of just 0.0007 ppm in the Earth's crust, with annual global production of only about 3 tons 3 . Copper presents a compelling alternative with significantly greater abundance.
At the heart of copper's effectiveness in OLEDs is a phenomenon called thermally activated delayed fluorescence (TADF). German researchers have recorded an incredibly fast intersystem crossing of just 27 picoseconds (27 trillionths of a second) 5 .
Top-emission OLEDs differ from conventional bottom-emission designs by emitting light through the top electrode rather than through the substrate.
Provides structural support and excellent electrical conductivity.
Injects positive charges (holes) into the device.
Where light is produced through recombination of charges using carbene-copper(I)-amide (CMA) complexes with photoluminescence quantum efficiencies up to 0.90 1 .
Facilitates injection of negative charges (electrons).
Semi-transparent electrode that allows light to escape while completing the electrical circuit.
Light emission occurs through the top layers in TEOLED architecture
One of the most significant challenges in TEOLED development has been thermal degradation—the tendency of pixels to shrink and performance to decline under operational heat stress.
The experimental results demonstrated dramatic improvements in thermal stability. Devices showed significantly reduced pixel shrinkage and maintained performance under stressful thermal conditions .
| EIL Material | Cathode Material | Binding Energy (Ebind eV/atom) |
|---|---|---|
| MgF₂ | Ag | -0.66 |
| MgF₂ | Yb | -2.01 |
| Yb | Ag | -0.70 |
Data sourced from . The higher negative binding energy values indicate stronger adhesion between layers.
Fabricating high-performance TEOLEDs on copper substrates requires a carefully selected set of materials, each serving a specific function.
| Material | Function | Key Properties |
|---|---|---|
| Copper(I) complexes | Emissive layer/sensitizer | High photoluminescence quantum efficiency (up to 0.90), fast radiative decay rates (up to 2.7 × 10⁶ s⁻¹) 1 |
| MgF₂ (Magnesium Fluoride) | Electron injection layer | High surface energy (2.2 J/m²), strong binding with cathode metals |
| Ag:Yb alloy | Cathode material | Heavy atoms resist thermal migration, low work function (2.6 V) |
| AZO (Aluminum-doped Zinc Oxide) | Transparent conductive oxide | More abundant and cost-effective than indium tin oxide (ITO) 6 |
| DMIC ligands | Carbazole donor ligands for copper complexes | Deuteriation and π-extension enhance stability and TADF properties 1 |
| Substrate Temperature (°C) | Average Peel Force (N/mm) | Relative Improvement |
|---|---|---|
| 25 | 0.2 | Baseline |
| 100 | 1.0 | 500% |
| 200 | 1.5 | 650% |
Data adapted from 6
The successful development of high-performance TEOLEDs on copper substrates opens up exciting possibilities for next-generation displays and lighting.
Copper substrates enable more durable, bendable displays for rollable tablets and folding phones.
TEOLED architecture allows for see-through displays for augmented reality applications.
Color-stable white OLEDs using copper sensitizers have achieved exceptional performance with current efficiency of 47.8 cd A⁻¹ 4 .
Widespread adoption of copper in displays could significantly reduce reliance on scarce precious metals.
at 1000 cd m⁻² brightness for red OLEDs using copper(I) sensitizers 1
This represents a significant milestone in making copper-based OLEDs commercially viable.
The journey of copper from an alternative material to a star performer in OLED technology illustrates how innovation can transform fundamental constraints into opportunities. By leveraging copper's unique quantum properties and addressing thermal stability challenges through sophisticated layer engineering, researchers have unlocked a new era for display technology.
The work on TEOLEDs fabricated on copper substrates represents more than just incremental improvement—it demonstrates a fundamental shift toward sustainable, high-performance electronics that don't compromise on quality or longevity. As these technologies mature and reach consumers, we may soon look back at precious metal-based displays as a relic of a less efficient, less sustainable past.