“…In recent years, solid-state red to near-infrared (NIR)-emitting materials as candidates of light sources have attracted a lot of attention, which can be used for bioimaging and labeling of human body tissues. − In addition, light-emitting electrochemical cells (LECs) have emerged as a viable option for inexpensive optical applications in the last two decades. − So far, many molecules, including polymers, − organic small molecules, , macromolecules, ionic transition-metal complexes (iTMCs), − and quantum dots, , have been used as emitters in LECs. However, the unique photophysical properties of iTMCs, such as the high external quantum efficiency (EQE) and long half-time, especially Ir(III) organometallic complexes, , Cu(I) complexes, , and Ru(II) polypyridine complexes, have led to the design of new derivatives. Nevertheless, various iTMCs such as Pd(II), Zn(II), Pt(II), Ir(III)–Au(I), and Ru(II)–Ag(I) have also been used in LECs as an emitter. ,,,, In film-processing, iTMCs are very useful because a single component is used in the film, and it acts as a charge transport and emissive material.…”