Tuning the structures of polypyridinium salts as bifunctional cathode interfacial layers for all-solution-processed red quantum-dot light-emitting diodes

Self-doping cathode interfacial layers (CILs) with both favorable electron injection and transport characteristics meet the key requirement for realizing high-performance optoelectronic devices with simplified structures. Herein, four different polypyridinium salts with tunable backbones, side chains and counterions are elaborately designed to afford them desirable film-forming property, polarity, structural rigidity and self-doping feature. All-solution-processed red quantum dot light-emitting diodes (QLEDs) employing them as bifunctional CILs render remarkably improved device performances in contrast to the typical CIL material of poly[(9,9-bis(30-( N , N -dimethylamino)propyl)-2,7-fluorene)- alt -2,7-(9,9-dioctylfluorene)] (PFN). The maximum external quantum efficiency of 2.74% achieved in this work represents one of the best values among the all-solution-processed QLEDs with individual organic CILs.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of MateriaMedica, Chinese Academy of Medical Sciences.