Synthetic Strategy for the Development of Conjugated Polyelectrolytes as Cathode Interfacial Layers: Toward Sustainable Organic Devices

Abstract The use of conjugated polyelectrolytes (CPEs) as interfacial layers (ILs) to increase the efficiency of organic light‐emitting diodes (OLEDs), organic solar cells (OSCs), and organic transistors is a well‐established strategy. Here, the rational process is reported that led to develop the bifunctional poly[(2,7‐(9,9’‐bis(6’‐diethoxylphosphorylhexyl)‐fluorene)‐alt‐(2,7‐(9,9′‐bis(6″‐trimethylammonium bromide)hexyl)‐fluorene)] (PF‐NBr‐EP). PF‐NBr‐EP is successfully incorporated as a cathode IL (CIL) in diverse electronic and optoelectronic devices. The properties of two fluorene‐based CPEs containing, respectively, phosphonate (EP) and ammonium (NBr) moieties used as building blocks for the synthesis of the PF‐NBr‐EP copolymer and their mixtures are investigated to evaluate the combined effect of the two moieties and therefore to gain insight into the behavior of PF‐NBr‐EP chemical structure in the devices. Additionally, the performance of OLEDs and OSCs is analyzed based on established active layers, incorporating all these neat and mixed CILs.