Organogels for low-power light upconversion

We herein report new organogels that permit efficient optical upconversion (UC) by triplet–triplet annihilation. The materials studied consist of a liquid organic phase, composed of a mixture of N,N-dimethylformamide and dimethyl sulfoxide in which the UC chromophore pair Pd(II) mesoporphyrin IX and 9,10-diphenylanthracene was dissolved, and a three-dimensional polymer network formed by covalently cross-linking poly(vinyl alcohol) with hexamethylene diisocyanate. The new gels are highly transparent, shape-persistent, and display efficient green-to-blue upconversion with UC quantum yields of >0.6 and 14% under ambient and oxygen-free conditions, respectively. The design approach presented here permits the fabrication of a hitherto unexplored class of materials with a unique combination of properties. The framework can easily be extended to other materials based on other solvents, polymer networks, and/or chromophore pairs.