Photon upconversion

Photon upconversion is a wavelength conversion technology that converts long wavelength low-energy light into shorter wavelength higher-energy light. By utilizing the photoexcited triplet with long lifetime, it is possible to upconvert weak intensity light such as sunlight with high efficiency. This is difficult to achieve by other methods and is a unique function of molecular materials

We started research on photon upconversion in 2012, and we have been working on the following two directions. We will continue to develop innovative and practical materials toward our goal of "a world where photon upconversion is all around us".

1. proposal of a new mechanism: from molecular diffusion to energy migration

Conventional photon upconversion research has mainly used molecular diffusion in solution, which requires volatile organic solvents, strict deoxygenation, and limited diffusion in the solid state. We have proposed a change of concept from molecular diffusion to energy migration and have demonstrated the concept in a variety of molecular assemblies such as non-volatile liquids, ionic liquids, gels, supramolecular assemblies, glasses, and crystals.

【Recent Examples】

Bicontinuous porous monolith：Chem. Sci., 2024, 15, 11500 - 11506.

Epoxy resin：ACS Appl. Mater. Interfaces 2022, 14, 22771–22780.

Gelatin gel：J. Am. Chem. Soc. 2018, 140, 10848-10855.

Crystalline film：J. Am. Chem. Soc. 2018, 140, 8788-8796.

Aqueous supramolecules：Chem. Sci, 2016, 7, 5224-5229.

Inoic liquid：Angew. Chem. Int. Ed., 2015, 54, 11550-11554.

Supramolecular gel：J. Am. Chem. Soc., 2015, 137, 1887-1894.

Non-volatile liquid：J. Am. Chem. Soc., 2013, 135, 19056-19059.

2. making the impossible possible with new molecules: near-infrared to visible and visible to ultraviolet conversion

Near-infrared-to-visible upconversion is strongly required for renewable energy generation such as solar cells and photocatalysts, and for photobiological applications such as optogenetics and photodynamic therapy. Visible-to-UV upconversion is also expected to be used for artificial photosynthesis, environmental purification, and antibacterial and antiviral applications.

We have succeeded in efficiently upconverting near-infrared light to visible light using only molecules, based on our original idea of using S-T absorption. We also reported the first optogenetics using molecular upconversion.

Recently, we have been focusing on the development of visible-to-ultraviolet upconversion chromophores, and have succeeded in developing new molecules that can function under sunlight and indoor light.

【Recent examples】

S-T absorption for NIR-to-vis upconversion：J. Am. Chem. Soc., 2016, 138, 8702-8705.

NIR-to-blue upconversion：J. Mater. Chem. C. 2017, 5, 5063-5067.

NIR-to-violet upconversion：Chem. Commun. 2020, 56, 7017-7020.

Molecular optogenetics：Angew. Chem. Int. Ed. 2019, 58, 17827-17833.

Vis-to-UV upconversion：Angew. Chem. Int. Ed. 2020, 60, 142-147.

Heavy metal-free vis-to-UV upconversion：J. Mater. Chem. C 2022, 10, 4558.

Talks about photon upconversion：