Tetradentate Pt complexes for organic light-emitting diodes

Tetradentate Pt(II)-based organic phosphors have emerged as emitters with a performance in commercial devices comparable to that of Ir(III)-based phosphors and superior to that of bidentate or tridentate Pt(II) complexes. The higher rigidity around the Pt atom of the tetradentate ligands facilitates large distortions to suppress the nonradiative decay channel. Accordingly, the proper design of the tetradentate ligand has proved to be key to the light-emitting performance of Pt(II) complexes and has been diversified to upgrade the device performance. In this review article, recent progress of molecular design strategies for tetradentate Pt(II) complexes is described and future prospects of Pt(II) phosphors are proposed.