Three- and Two-Photon NIR-to-Vis (Yb,Er) Upconversion from ALD/MLD-Fabricated Molecular Hybrid Thin Films

We report blue, green, and red upconversion emissions with strongly angular-dependent intensities for a new type of hybrid (Y,Yb,Er)-pyrazine thin films realized using the atomic/molecular layer deposition thin-film fabrication technology. The luminescence emissions in our amorphous (Y,Yb,Er)-pyrazine thin films of a controllable nanothickness originate from three- and two-photon NIR-to-vis excitation processes. In addition to shielding the lanthanide ions from nonradiative de-excitation, the network of interconnected organic molecules serves as an excellent matrix for the Yb³⁺-to-Er³⁺ excitation energy transfer. This suggests a new approach to achieve efficient upconverting molecular materials with the potential to be used for next-generation medical diagnostics, waveguides, and surface-sensitive detectors.