Lin Y.-STsai H.-YHuang J.-K|CHING-FUH LIN2022-04-252022-04-25202120462069https://www.scopus.com/inward/record.uri?eid=2-s2.0-85121506406&doi=10.1039%2fd1ra06326j&partnerID=40&md5=16eb268c5bb3a312430c2047616f4a05https://scholars.lib.ntu.edu.tw/handle/123456789/607031Compared with rare earth elements and heavy metal elements, rare-earth-element-free fluorescent films can greatly reduce environmental hazards. In this study, we use a solution method to produce the fluorescent films. The film thickness is 10 μm, which can maintain fluorescent light intensity in an environment with an average humidity of 55.1 (RH%) after encapsulation. We also find that the type of solvent affects the resonance position of the C-N functional group in DCJTB at a wavenumber of 2196 (cm?1), measured with Fourier transform infrared spectroscopy. The functional group is affected by the polar effect with its displacement decreasing with the quantum yield. Finally, we successfully made a fluorescent solution with a resonance displacement of only 12.8 (cm?1) for the C-N functional group with the quantum yield being as high as 81.3% and a fluorescent film with a quantum yield as high as 84.8%. ? The Royal Society of Chemistry 2021.Fourier transform infrared spectroscopyHeavy metalsQuantum yieldRare earth elementsRare earthsResonanceBasic groupsElement-freeEnvironmental hazardsFilm-thicknessFluorescent lightGroup resonanceHeavy metal elementsHigher efficiencyRed lightSolution methodsFluorescence[SDGs]SDG7journal article10.1039/d1ra06326j2-s2.0-85121506406