Long‐Wavelength Light‐Emitting Electrochemical Cells: Materials and Device Engineering

Abstract

Long‐wavelength light‐emitting electrochemical cells (LECs) are potential deep‐red and near infrared light sources with solution‐processable simple device architecture, low‐voltage operation, and compatibility with inert metal electrodes. Many scientific efforts have been made to material design and device engineering of the long‐wavelength LECs over the past two decades. The materials designed the for long‐wavelength LECs cover ionic transition metal complexes, small molecules, conjugated polymers, and perovskites. On the other hand, device engineering techniques, including spectral modification by adjusting microcavity effect, light outcoupling enhancement, energy down‐conversion from color conversion layers, and adjusting intermolecular interactions, are also helpful in improving the device performance of long‐wavelength LECs. In this review, recent advances in the long‐wavelength LECs are reviewed from the viewpoints of materials and device engineering. Finally, discussions on conclusion and outlook indicate possible directions for future developments of the long‐wavelength LECs. This review would like to pave the way for the researchers to design materials and device engineering techniques for the long‐wavelength LECs in the applications of displays, bio‐imaging, telecommunication, and night‐vision displays.

Biphenyl Au(III) Complexes with Phosphine Ancillary Ligands: Synthesis, Optical Properties, and Electroluminescence in Light-Emitting Electrochemical Cells

“…A wide variety of LECs employing iridium complexes delivering blue, green, yellow, orange, red, near infrared (NIR), and white emission have been published. With judicious molecular design and device engineering, some reported iridium-based LECs have reached high external quantum efficiencies (EQEs) up to or higher than 20%. − The ruthenium complex was the first iTMC used for LECs, but the ruthenium-based LECs generally showed red to NIR electroluminescence (EL) spectra, and the maximum EQEs were around only 1% . The LECs employing a Pt porphyrin, a Pt­(II) dimer, and a dinuclear Ir­(III)/Pt­(II) complex exhibited red to NIR EL, and the maximum EQE achieved with the host–guest strategy was up to 2.7% .…”

Cationic Ir(III) Complexes with 4-Fluoro-4′-pyrazolyl-(1,1′-biphenyl)-2-carbonitrile as the Cyclometalating Ligand: Synthesis, Characterizations, and Application to Ultrahigh-Efficiency Light-Emitting Electrochemical Cells

“…Crystal data, 1 H and 13 C NMR spectra, transient PL curves, TD-DFT calculation, high resolution mass spectra, LECs performance on DTBP with various EML thickness, and synthetic procedure and characterization data of the complexes (PDF)…”

“…7−13 More importantly, the introduction of a rigid ligand can improve high phosphorescence quantum yields (QYs) leading to realize the high efficiency of LECs device. [7][8][9][10][11][12][13]18,19 With these advantages, cationic Ir(III) complexes have found extensive applications in various aspects of LECs.…”

Copper(i) iodide coordination polymers with triazole substituted pyridine ligands: photophysical and electrical conductivity properties

“…1–7 In particular, copper( i ) complexes are subjected to extensive study for their practical application in organic light-emitting diodes, light-emitting electrochemical cells, biological sensors, molecular wires, non-linear optics, electrically conductive materials, thermochromic sensors, etc. 8–14 Complexes and coordination polymers (CPs) derived from copper( i ) iodide with nitrogen, sulphur and phosphorous-containing ligands have emerged as promising candidates for multifunctional materials with variable photophysical and electrical properties and provide an alternative way to synthesize affordable and environmentally benign materials. 15–21 Furthermore, the structural diversity of copper halide complexes/CPs can also depend upon the coordinating ligands, metal-to-ligand ratios, and reaction conditions (temperature, pressure, etc.…”