Transparent organic/inorganic nanocomposites for tunable full-color upconversion

Abstract

A transparent medium that gives emission covering the entire color space may find applications in fields such as displays and photonics. However, it is technically difficult to access these materials through the combination of emission spectra from different codoped ions in a single host, as energy transfer via inter-ion coupling is unavoidable. Here we demonstrate a simple method for realizing tunable upconversion (UC) emission through a nanocrystal (NC)–polymer nanocomposite. In our process, the wet-chemistry derived NaYF₄:RE (RE: rare earth) NCs with pure red, green and blue UC emission were incorporated into a polymer matrix at a concentration that efficiently suppresses inter-particle coupling, such that the emissions from each NC are well preserved. The combination of emissions from different types of NCs with selected ratios, therefore, is able to produce emission spectra at any color coordinate in a predictable manner. The emission color of this composite can be further tuned by the pumping intensity of the near infrared laser as well as the density of the NCs in the composite. The method demonstrated here may find applications in both 2D and 3D display technologies and related photonic devices.