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

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.