Green and warm-white light-emitting diodes enabled by zero-dimensional green-emitting Mn(II) bromide complex with record high efficiency

Abstract

Low-dimensional, earth-abundant, non-toxic, and crystalline materials are highly promising candidates for organic light-emitting diodes (OLEDs). Here, we report a zero-dimensional (0D) Mn(II) complex, [Ph3BzP]2[MnBr4] (MnBz) synthesized using a solvent-free mechanochemical grinding method. MnBz exhibits a bright and narrow green emission peak at 517 nm originating from the discrete [MnBr4]2− unit separated by large hydrophobic quaternary phosphonium ions in solid state, with excellent stability and a remarkably high PLQY of 53%. Theoretical calculations indicate that the conduction band derives from the C-2p (benzene ring) and Mn-3d states, while the valence band originates from the Br-4p and Mn-3d states. Green phosphorescent OLEDs (PHOLEDs) based on the 0D MnBz exhibit an excellent external quantum efficiency and current efficiency of 11.42% and 56.84 cd A−1, respectively, thus outperforming the currently available Mn(II) complex-based OLEDs. Furthermore, for the first time, an RGB warm-white OLED is fabricated using the Mn(II) complex as the green component, exhibiting an excellent CRI of 78 with a CCT of 3740 K. This successful development of a high-performance, stable green-PHOLED using MnBz while also demonstrating its potential as an emitter candidate for white OLEDs, may inspire the future development of cheaper alternatives for a variety of emission applications and commercial display devices. © 2023 Elsevier B.V.