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Kyushu University Achieves 1.9% Visible-to-UV Upconversion for Solar Applications

6/24/2026

Summary

Kyushu Scientists Upconvert

Kyushu University scientists in Japan created a solid material that upconverts two visible photons into one UV photon using sunlight.
The material, a semiconductor dihydroindenoindenedene (DHI) with alkyl spacers, achieved 1.9% upconversion efficiency and fluorescence yields up to 83%.
The researchers filed a patent and published the findings in Nature Communications on June 23 2026.
Potential uses include solar-driven air purification, low-intensity 3D printing and dental curing, with UV about 6% of sunlight.

Summary

Kyushu Scientists Upconvert

Scanning electron microscopy shows Ir(ppy)3 and nitrogen atoms are evenly dispersed in spin-coated iBu-DHI crystals, avoiding segregation.
Metal-free TADF sensitizers 4CzIPN and DABNA enable visible-to-UV upconversion in iBu-DHI films, removing iridium complexes.
Alkyl groups on DHI raise quantum yields to 69-83 %, extend triplet lifetimes to 7.8 ms, lower Ith to 0.7 mW cm?², and create packing blocking oxygen diffusion, letting the iBu-DHI/Ir(ppy)3 film emit upconversion in air for an hour under 2.0 W cm?².

History

Historical Context

Building on the 1999 University of Tokyo–Kyoto University demonstration of triplet-triplet annihilation upconversion, Kyushu University’s 2026 iBu-DHI platform extended triplet lifetimes and raised conversion efficiency, enabling a significant reduction in solar energy losses. The breakthrough prompted funding from Japan’s Ministry of Economy, Trade and Industry, linking early upconversion research to national renewable-energy goals.

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Kyushu Scientists Upconvert

Kyushu University scientists in Japan created a solid material that upconverts two visible photons into one UV photon using sunlight.
The material, a semiconductor dihydroindenoindenedene (DHI) with alkyl spacers, achieved 1.9% upconversion efficiency and fluorescence yields up to 83%.
The researchers filed a patent and published the findings in Nature Communications on June 23 2026.
Potential uses include solar-driven air purification, low-intensity 3D printing and dental curing, with UV about 6% of sunlight.

1 / 3