This article digs into a new plasmonics-enhanced approach to solid-state triplet-fusion upconversion from researchers at Princeton University and North Carolina State University. They used nanoscale silver films to boost light–matter interactions and found a way to efficiently convert low-energy light into higher-energy light with way less input power than before. That opens up some interesting possibilities for advanced optoelectronic devices, like OLEDs.
Why Solid-State Upconversion Has Been a Longstanding Challenge
Photon upconversion—turning two or more low-energy photons into a single higher-energy photon—has been a hot topic for decades. People hope to use it for everything from solar energy to bioimaging and displays.
Triplet-fusion upconversion stands out because, in theory, it works under low-light conditions. But in solid materials, molecules can’t really move around. That makes it hard for the interactions needed for efficient triplet fusion to happen, so researchers have had to use extremely intense light sources. Because of this, most efficient upconversion has only worked in liquid systems, not solid-state devices.
Harnessing Plasmonics to Amplify Light Absorption
This new work sidesteps that roadblock with plasmonic enhancement. The team put a thin silver film under the upconversion layer. When you shine light on it, the film supports surface plasmons—basically, collective wobbles of free electrons—that really ramp up the local electromagnetic field.
Tenfold Absorption Enhancement at the Molecular Level
This stronger field means upconversion molecules are much more likely to absorb incoming photons. Their measurements showed about a tenfold jump in light absorption, which increased the number of excited triplet states in the solid.
That boost made efficient triplet fusion possible without blasting the material with intense light. Compared to a similar setup without the plasmonic film, the plasmon-enhanced structure cut the optical power needed for upconversion by a factor of 19. That’s a pretty serious upgrade.
Lower Power, Higher Impact
From a device-engineering angle, needing less input power is a game changer. High-intensity light sources are bulky, wasteful, and just not practical for most real-world tech. By using plasmonics instead of brute-force illumination, the researchers found a more elegant and scalable way forward.
Why This Matters for Optoelectronics
Efficient solid-state upconversion at low power could shake up a few fields, including:
A Practical Demonstration in White OLEDs
To show this isn’t just theory, the team built the plasmonic upconversion layer into an organic light-emitting diode (OLED). The upconversion system made blue light, which they combined with regular green and red OLED emission to get white light.
Addressing the Blue OLED Stability Problem
Blue OLEDs are tough to work with—they need high-energy excitations and tend to break down faster than red and green ones. By generating blue light through low-energy excitation and upconversion, this approach could offer a thin-film, stable blue source without relying on rare or fragile materials.
Looking Ahead: Optimization and Future Research
This work, published in Nature Photonics and led by Barry Rand, is a solid proof of principle. The authors point out there’s still room for improvement with better plasmonic films and smarter optical designs.
Training the Next Generation of Scientists
Beyond its technical achievements, the project became a powerful training ground for young researchers. Undergraduate students from Princeton jumped right into experimental work and picked up hands-on experience with advanced nanofabrication.
They also learned a lot about optical characterization. Honestly, that’s a real investment in the future of the field.
Here is the source article for this story: Optics research uses dim light to produce bright LEDs