Single component white-OLEDs derived from tris(β-diketonato) europium(iii) complexes bearing the large bite angle N^N 2-(4-thiazolyl)benzimidazole ligand

Rashid Ilmi, Jiaxuan Yin, José D. L. Dutra, Nawal K. Al Rasbi, Willyan F. Oliveira, Liang Zhou, Wai-Yeung Wong, Paul R. Raithby, Muhammad S. Khan

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Abstract

Two new organo-europium complexes (OEuCs) [Eu(tfac)3(TB-Im)] (Eu1) [Eu(hfac)3(TB-Im)] (Eu2) incorporating fluorinated (hexafluoroacetylacetone; Hhfaa) or hemi-fluorinated (trifluoroacetylacetone; Htfac) β-diketones together with the large bite angle N^N ligand (2-(4-thiazolyl)benzimidazole; TB-Im) have been synthesized and characterized. The structure of the complexes has been established by single crystal X-ray diffraction (SC-XRD) analysis and shows that the coordination sphere is composed of a EuO6N2 core (octacoordinated). Continuous shape measures (CShMs) revealed that the geometry around Eu(III) is trigonal dodecahedral with approximate D2d-symmetry. Efficient red emission is observed for both the complexes in solution with a fairly large photoluminescence quantum yield (PLQY (QLEu) = 39.00–47.00%). Furthermore, by utilizing the experimental photoluminescence (PL) data and theoretical modelling employing density functional theory (DFT) in conjunction with LUMPAC, energy transfer (ET) and back energy transfer rates were calculated, and an ET mechanism for the sensitized PL is proposed and discussed in detail. Finally, the complexes were used as an emitting layer (EML) to fabricate 20 organic light emitting diodes (OLEDs) by varying the doping concentration. Interestingly, both the complex-based OLEDs at 4 wt% doping concentration display white electroluminescence (EL) with the brightness (B) = 100.5–364.1 cd m−2 at very low turn-on voltage (Vturn-on) = 3.9–4.6 V. The overall electroluminescence performance of Eu1 and Eu2 is higher than that of the reported europium based single component white-OLEDs.
Original languageEnglish
Pages (from-to)14228-14242
Number of pages15
JournalDalton Transactions
Volume51
Issue number37
Early online date30 Aug 2022
DOIs
Publication statusPublished - 7 Oct 2022

Bibliographical note

Funding Information:
MSK acknowledges His Majesty's Trust Fund for Strategic Research (Grant No. SR/SQU/SCI/CHEM/21/01) for funding. RI thanks HM's Trust Fund for a postdoctoral fellowship. JDLD appreciates the financial support from the Brazilian funding agencies: CAPES, CNPq (421733/2018-7), FACEPE (APQ - 0675-1.06/14) and FAPITEC-SE (Process N. 019.203.01074/2011-1). WFO thanks PIBIC/CNPq/UFS for a scientific initiation fellowship. The computing for this project was performed on the LCAD-UFS (UFS High Performance Computing Laboratory). LZ is grateful for the financial aid from the National Natural Science Foundation of China (62174160), Youth Innovation Promotion Association of the Chinese Academy of Sciences (2013150). WYW thanks the Hong Kong Research Grants Council (PolyU 153058/19P), Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials (2019B121205002), the CAS-Croucher Funding Scheme for Joint Laboratories (ZH4A), Hong Kong Polytechnic University (1-ZE1C), Research Institute for Smart Energy (CDAQ) and the Endowed Professorship in Energy from Miss Clarea Au (847S) for the financial support. PRR is grateful to the Engineering and Physical Sciences Research Council (EPSRC) for funding (Grant EP/K004956/1).

Publisher Copyright:
© 2022 The Royal Society of Chemistry.

Funding

MSK acknowledges His Majesty's Trust Fund for Strategic Research (Grant No. SR/SQU/SCI/CHEM/21/01) for funding. RI thanks HM's Trust Fund for a postdoctoral fellowship. JDLD appreciates the financial support from the Brazilian funding agencies: CAPES, CNPq (421733/2018-7), FACEPE (APQ - 0675-1.06/14) and FAPITEC-SE (Process N. 019.203.01074/2011-1). WFO thanks PIBIC/CNPq/UFS for a scientific initiation fellowship. The computing for this project was performed on the LCAD-UFS (UFS High Performance Computing Laboratory). LZ is grateful for the financial aid from the National Natural Science Foundation of China (62174160), Youth Innovation Promotion Association of the Chinese Academy of Sciences (2013150). WYW thanks the Hong Kong Research Grants Council (PolyU 153058/19P), Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials (2019B121205002), the CAS-Croucher Funding Scheme for Joint Laboratories (ZH4A), Hong Kong Polytechnic University (1-ZE1C), Research Institute for Smart Energy (CDAQ) and the Endowed Professorship in Energy from Miss Clarea Au (847S) for the financial support. PRR is grateful to the Engineering and Physical Sciences Research Council (EPSRC) for funding (Grant EP/K004956/1).

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