Efficient narrow band pure red emitting molecular europium complexes for white light-emitting diode and anticounterfeiting applications

Abstract

The luminescent ternary Eu(III) complexes of phenanthro-imidazole derivatives and dibenzoylmethane (DBM), Eu(DBM)₃Phen-pCH₃-mCF₃ and Eu(DBM)3Phen-pCH₃-p-CH₃, were synthesized and explored for versatile applications. Phenanthro-imidazole derivatives and their respective Eu(III) complexes were well characterized, and their electrochemical and photophysical properties were successfully studied. The PL emission spectra of the ligands showed blue emission, whereas the Eu(III) complexes showed red emission in the solid phase. In the solution phase, the Eu(DBM)₃Phen-pCH₃-mCF₃ complex showed multiple emission (near white emission). The energy transfer mechanism was better understood through theoretical (DFT/TD-DFT) calculations. Light-emitting diodes (LEDs) were fabricated by conjugating the Eu complexes with near UV LEDs. The obtained results were very close to the National Television System Committee (NTSC) standard for pure red emission. LED fabrication using Eu(DBM)₃Phen-pCH₃-pCH₃ with a 1 : 50 ratio showed near white emission with the CIE color coordinates x = 0.32 and y = 0.38, a CRI of 80 and a CCT of 5912 K. In addition, the presently studied Eu(III) complexes show excellent anticounterfeiting and sensing applications.