Researchers Achieve 1.9% Solid-State Visible-to-UV Upconversion at 1.2 mW/cm2
Updated
Updated · Nature.com · Jun 23
Researchers Achieve 1.9% Solid-State Visible-to-UV Upconversion at 1.2 mW/cm2
3 articles · Updated · Nature.com · Jun 23
Summary
A crystalline film built from isobutyl-substituted DHI and Ir(ppy)3 delivered 1.9% absolute visible-to-UV upconversion efficiency with a 1.2 mW/cm2 threshold—below roughly 1.4 mW/cm2 solar irradiance near 445 nm.
Alkyl chains placed above and below the π-system suppressed singlet and triplet quenching while preserving fast triplet diffusion, solving a long-standing solid-state tradeoff between high fluorescence yield and exciton transport.
Among three DHI derivatives tested, iBu-DHI performed best in both solution and solid form, reaching 10% upconversion yield in solution and showing defect-tolerant fluorescence, long triplet lifetimes and uniform donor dispersion in films.
A drop-cast version cut the threshold further to 0.7 mW/cm2, while annealing reduced emission by causing sensitizer segregation, underscoring the importance of crystallinity and controlled doping.
The advance could broaden solvent-free sunlight harvesting for photocatalysis and other UV-driven applications, and the team said the same crystal design also worked with metal-free sensitizers.
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Record 1.9% Efficiency in Solid-State Visible-to-UV Upconversion: Kyushu University’s Game-Changing Solar Innovation
Overview
Researchers at Kyushu University, led by Professor Nobuo Kimizuka, have developed a novel solid-state material that can convert ordinary visible sunlight into ultraviolet light with a record efficiency of 1.9 percent. This breakthrough operates under everyday conditions without the need for high-intensity lasers or special optics, marking a major advance in photon upconversion technology. The achievement is the result of extensive long-term research and stands out because most other materials struggle to work at low light levels or require complex equipment. This innovation opens new possibilities for sustainable and practical applications using sunlight.