Synthesis and light-emitting properties of copolymers composed of fluorene and N-alkoxyphenylphenothiazine

Poly[10-(4′-octyloxyphenyl)-phenothiazine-3,7-diyl] (POPPTZ), poly[9,9-bis(4′-octyloxyphenyl)fluorene-2,7-diyl] (PBOPF), and their random copolymers, poly(BOPF-co-OPPTZ), were synthesized through Ni(0) mediated polymerization. Light-emitting devices were fabricated using these polymers in an ITO (indium-tin oxide)/PEDOT:PSS/polymer/Ca/Al configuration. Each EL device constructed with a poly(BOPF-co-OPPTZ) copolymer exhibited significantly enhanced efficiency and brightness compared to devices constructed from the POPPTZ and PBOPF homopolymers. The EL device constructed with poly(83BOPF-co-17OPPTZ) exhibited the highest power efficiency and brightness (8,610 cd/m2 and 2.831 cd/A, respectively). This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arise due to the HOMO levels (∼5.42 eV) of the poly(BOPF-co-OPPTZ) copolymers, which are lower than that of the PBOPF homopolymer (∼5.79 eV).