Light-emitting electrochemical cells (LECs) are solution-processable thin-film electroluminescent devices consisting of a luminescent material in an ionic environment. The simplest type of LEC is based on only one material, ionic transition-metal complexes (iTMCs). These materials are of interest for different scientific fields such as chemistry, physics, and technology as selected chemical modifications of iTMCs resulted in crucial breakthroughs for the performance of LECs. This short review highlights the different strategies used to design these compounds with the aim to enhance the performances of LECs.