Outstanding Circularly Polarized TADF in Chiral Cu(I) Emitters: From Design to Application in CP‐TADF OLEDs

Low‐cost molecular emitters that merge circularly polarized luminescence (CPL) and thermally activated delayed fluorescence (TADF) properties are attractive for many high‐tech applications. However, the design of such emitters remains a difficult task. To address this challenge, here, we propose a simple and efficient strategy, demonstrated by the design of pseudochiral‐at‐metal complexes [Cu(L*)DPEPhos]PF6 bearing a (+)/(–)‐menthol‐derived 1,10‐phenanthroline ligand (L*). These complexes exhibit a yellow CP‐TADF with a record‐high quantum yield (close to 100%) and high dissymmetry factor (|glum| ~ 1×10–2). Remarkably, the above compounds also show a negative thermal‐quenching (NTQ) of luminescence in the 300–77 K range. Exploiting the designed Cu(I) emitters, we fabricated efficient CP‐TADF OLEDs displaying mirror‐imaged CPL bands with high |gEL| factors of 1.5×10–2 and the maximum EQE of 6.15%. Equally important, using the (+)‐[Cu(L*)DPEPhos]PF6 complex, we have discovered that an external magnetic field noticeably suppresses CP‐TADF of Cu(I) emitters. These findings are an important contribution to the CPL phenomenon and provide access to highly efficient, low‐cost and robust CP‐TADF emitters.