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

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.