Enhanced Performance of All‐Solution Processed Multilayer OLEDs by Photoluminescence Lifetime Reduction of Cu(I) Complex Emitters Containing Chalcogenolate‐Diimine Ligands

Abstract Luminescent and solution‐processable copper(I) complexes offer the perspective of obtaining devices that combine efficiency and stability at low production costs. Here, we investigate Cu(I) complexes with phosphine and 1,10‐phenanthroline‐derived ligands, which show thermally activated delayed fluorescence (TADF) and phosphorescence applied to all‐solution processed multilayer OLEDs. Unsubstituted, thiadiazole‐substituted and selenodiazole‐substituted phenanthroline ligands were compared to evaluate the potential of the incorporation of sulfur and selenium atoms to enhance the device performance. A shortening of the photoluminescence lifetime of the selenium‐containing emitter was found to compensate this emitter's lower emission yield, leading to devices of comparable performance to devices based on the more efficiently emitting unsubstituted phenanthroline complex. The results indicate that the emission lifetime reduction is a promising approach to improve OLEDs based on solution‐processable Cu(I) complexes.