Plasmon Technology Breakthrough Enables Record-Low Threshold Upconversion for Advanced Displays

Revolutionary Plasmon Enhancement Cuts Energy Threshold

Researchers have reportedly achieved a major advancement in photon upconversion technology using surface plasmons to dramatically reduce energy requirements, according to a recent study published in Nature Photonics. Sources indicate that the new approach lowers the intensity threshold by a factor of 19 while increasing external quantum efficiency by 17 times compared to conventional methods.

Revolutionary Plasmon Enhancement Cuts Energy Threshold
Innovative Device Architecture
OLED Integration Enables Practical Applications
High-Performance White OLED Demonstration
Performance Metrics and Future Optimization

The breakthrough system achieves intensity thresholds as low as 3.4 mW cm⁻² with external quantum efficiency reaching 0.094%, analysts suggest. This significant improvement stems from plasmon-enhanced absorption that enables more efficient triplet fusion upconversion, a process where lower-energy photons combine to create higher-energy light.

Innovative Device Architecture

The research team developed a sophisticated multilayer structure built on a silver film with an aluminum seed layer, according to the report. The architecture features a 4.4-nm sensitizer layer containing platinum(II) octaethylporphyrin (PtOEP) doped into DMPPP, topped with a 30-nm emitter layer of BDAVBi doped into MADN annihilator. A final 1.5-nm mCP layer prevents crystallization, with the total thickness kept under 40 nm to maintain optimal plasmon momentum matching.

Experimental results showed surface plasmon resonance occurring at a 72° incident angle, where reflectance reached zero and upconverted emission peaked, the report states. Researchers confirmed that transverse-electric-polarized light produced no upconversion, demonstrating that surface plasmons exclusively drive the emission process in this configuration.

OLED Integration Enables Practical Applications

Perhaps most significantly, the team successfully integrated the upconversion technology with organic light-emitting diodes, creating a compact thin-film device that eliminates the need for bulky optical components. Analysis indicates that excitons in the OLED’s emissive layer generate surface plasmons in the aluminum/silver cathode, which then excite the upconversion film.

When operating at higher current densities, the device exhibits a distinct emission feature at 460 nm corresponding to upconverted blue light matching BDAVBi photoluminescence, according to the findings. Control experiments with the sensitizer layer positioned farther from the cathode showed no upconversion, confirming the plasmon-mediated nature of the process.

High-Performance White OLED Demonstration

The research team demonstrated the practical potential of this technology by creating white OLEDs that use blue emission from plasmon-excited upconversion rather than conventional blue electroluminescence. The report states these devices achieved a color rendering index of up to 86.2 and CIE coordinates of (0.376, 0.472) at 40 mA cm⁻² current density.

This approach offers significant advantages over existing WOLED technologies, analysts suggest, because blue emission occurs without injected charges or high-energy triplet states. This reportedly circumvents triplet-triplet and triplet-polaron annihilation events that typically cause phosphorescent blue OLED degradation.

Performance Metrics and Future Optimization

The OLED-excited upconversion system demonstrated an 11.5-fold decrease in threshold compared to far-field excitation, with values of 4.1 mW cm⁻² versus 46.9 mW cm⁻² respectively. Researchers note that this enhancement is primarily attributed to improved absorption, though it falls somewhat short of the 19-fold improvement seen in Kretschmann geometry experiments.

The white OLED prototype reached peak values of 0.31% external quantum efficiency and 1,600 cd m⁻² luminance, according to the report. Future work will focus on optimizing device performance to approach state-of-the-art WOLED efficiencies of 20-30% through improved plasmon coupling, more efficient upconversion films, and enhanced outcoupling of upconverted emission.

Industry observers suggest this technology could have significant implications for display and lighting applications, particularly where color quality and operational stability are critical concerns. The demonstration of efficient upconversion driven by OLED-generated plasmons reportedly opens new possibilities for advanced photonic devices without requiring external laser excitation.

References

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