D-A-based polyfluorene derivatives end-capped with cyclometalated iridium complexes by unconjugated linkage: Structure–property relationships

A series of donor(D)-acceptor(A)-based polyfluorene derivatives, which contain carrier-transporting units of carbazole and oxadiazole as the substitutes of the C-9 position of fluorene and are end-capped with the red-emitting iridium bi(phenylisoquilonato)(picolinato) unit by unconjugated linkage, were synthesized and characterized. The molar ratios between the donor of carbazole and the acceptor of oxadiazole moieties were found to significantly influence photoluminescent efficiency, electrochemical and electroluminescent properties of these D-A-based polyfluorene derivatives. While the ratio increased to 3:7, the PFCz3OXD7Ir showed the best device performance in the polymer light-emitting device with a configuration of ITO/PEDOT/polymers/LiF/Al. A turn-on voltage of 6.0 V, a maximum current efficiency of 0.59 cd/A and the highest luminance of 917 cd/m2 were presented.