Efficient photon upconversion enabled by strong coupling between silicon quantum dots and anthracene

Hybrid structures formed between organic molecules and inorganic quantum dots can accomplish unique photophysical transformations by taking advantage of their disparate properties. The electronic coupling between these materials is typically weak, leading photoexcited charge carriers to spatially localize to the dot or to a molecule at its surface. However, we show that by converting a chemical linker that covalently binds anthracene molecules to silicon quantum dots from a carbon–carbon single bond to a double bond, we access a strong coupling regime where excited carriers spatially delocalize across both anthracene and silicon. By pushing the system to delocalize, we design a photon upconversion system with a higher efficiency (17.2%) and lower threshold intensity (0.5 W cm–2) than that of a corresponding weakly coupled system. Our results show that strong coupling between molecules and nanostructures achieved through targeted linking chemistry provides a complementary route for tailoring properties in materials for light-driven applications. Hybrid structures made up of quantum dots functionalized with molecules are highly tunable platforms for light-driven applications; however, the interaction between their components is often weak. Now it has been shown that by connecting molecules to silicon quantum dots via p-conjugated tethers, strongly coupled exciton states can be generated that prove advantageous for photon upconversion.