Recent progress of narrowband iridium(III) complexes for organic light-emitting diodes

Phosphorescent iridium(III) complexes have emerged as the leading emitters in commercial organic light-emitting diodes, thanks to their high efficiency and outstanding operational stability. However, the inherently broad emission spectra of most Ir(III) complexes limit their color purity and hinder the realization of next-generation wide-gamut displays. Developing Ir(III) complexes that exhibit narrowband red (R), green (G), and blue (B) emission (full width at half-maximum <50 nm) is therefore critically important but remains comparatively underexplored. In this review, we summarize recent advances in narrowband Ir(III) phosphors, highlighting how molecular structure governs photophysical behavior and device performance. Key molecular design strategies aimed at balancing ligand-centered transition and metal-to-ligand transfer transition contribution and improving molecular rigidity to achieve a narrow emission spectrum of Ir(III) complexes are systematically outlined. We endeavor to elucidate the structure-property relationship in these Ir(III) complexes and to discuss rational molecular design for emitters with high color purity and excellent efficiency.