Full Solution Process of a Near-Infrared Light-Emitting Electrochemical Cell Based on Novel Emissive Ruthenium Complexes of 1,10-Phenanthroline-Derived Ligands and a Eutectic Alloy as the Top Electrode

Babak Pashaei; Hashem Shahroosvand; Hamed Douroudgari; Saeid Abaspour; Morteza Vahedpour; Mohammad Khaja Nazeeruddin

doi:10.1021/acs.inorgchem.2c02531

Full Solution Process of a Near-Infrared Light-Emitting Electrochemical Cell Based on Novel Emissive Ruthenium Complexes of 1,10-Phenanthroline-Derived Ligands and a Eutectic Alloy as the Top Electrode

Inorg Chem. 2023 May 22;62(20):7622-7635. doi: 10.1021/acs.inorgchem.2c02531. Epub 2023 May 10.

Authors

Babak Pashaei¹, Hashem Shahroosvand¹, Hamed Douroudgari², Saeid Abaspour¹, Morteza Vahedpour², Mohammad Khaja Nazeeruddin³

Affiliations

¹ Group for Molecular Engineering of Advanced Functional Materials, Department of Chemistry, University of Zanjan, Zanjan 45371-3879, Iran.
² Physical Chemistry, Department of Chemistry, University of Zanjan, Zanjan 45371-3879, Iran.
³ Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, Ecole Polytechnique F́ed́erale de Lausanne, Sion CH-1951, Switzerland.

PMID: 37163724
DOI: 10.1021/acs.inorgchem.2c02531

Abstract

Near-infrared luminescent materials have recently received considerable attention for a large number of applications, including in solid-state lighting, as bioimaging agents, as photovoltaic cells, and in the telecommunication industry. By adding diverse electron-donating or withdrawing groups on ancillary ligands based on benzenethiol-phenanthroline, we synthesized and optoelectronically characterized a series of novel ionic ruthenium complexes, namely RuS, RuSCl, RuSMe, and RuSNH₂, for using in a light-emitting electrochemical cell. The synthesized complexes are intense red emitters in the range of 584-605 nm in solution, which depends on the substitutions of electron donor/acceptor moieties on the ancillary ligands. To find a suitable quantum mechanical approach, benchmark calculations based on time-dependent density functional theory were carried out on these complexes. Our benchmark revealed that the M06-L method has results close to those of the experiment. Furthermore, to gain a deeper insight into electronic transitions, several excitation processes were investigated at the TD-DFT-SMD-MN12-L/gen level. The results showed that in the designed complexes, the dominant transition is between the 4d_Z² electron of Ru (particle) and the π* orbitals of the ancillary ligand (hole). The single-layer devices, including these complexes along with a Ga/In cathode by a facile deposition method without the addition of any electron or hole transport layers, were fabricated and displayed red (678 nm) to near-infrared (701 nm) emission as well as a decrease of turn-on voltage from 3.85 to 3.10 V. In particular, adding a methyl group to the ancillary ligand in the complex RuSNH₂ increases the external quantum efficiency to 0.55%, one of the highest observed values in the ruthenium phenanthroline family. This simple structure of the device lets us develop the practical applications of light-emitting electrochemical cells based on injection and screen-printing methods, which are very promising for the vacuum-free deposition of top electrodes.