A novel high-efficiency white hyperbranched polymer derived from polyfluorene with green and red iridium(III) complexes as the cores

Abstract

A new kind of single triple-color hyperbranched polymer PF-Ir(ppy)2(pytzph)m-Ir(piq)2(pytzph)n was designed and synthesized, in which green and red iridium(III) complexes acted as cores and blue polyfluorene acted as backbone. PF-Ir(ppy)2(pytzph)m-Ir(piq)2(pytzph)n (m = 5, n = 5 and m = 25, n = 5) had higher quantum efficiency than PF-Ir(piq)2(pytzph)5. The energy transfer from green core bis(2-phenylpyridine)[3-(2-pyridyl)-5-phenyl-1,2,4-triazole]iridium(III) [Ir(ppy)2(pytzph)] with high triplet energy level (ET = 2.58 eV) to red core bis(1-phenylisoquinolinato)[3-(2-pyridyl)-5-phenyl-1,2,4-triazole]iridium(III) [Ir(piq)2(pytzph)] (ET = 2.12 eV) could realize by intermediate poly(9,9-dioctylfluorene) (PF) segments. A typical single emitting-layer device with the configuration of ITO/PEDOT:PSS (40 nm)/PF-Ir(ppy)2(pytzph)m-Ir(piq)2(pytzph)n (80 nm)/TPBi (40 nm)/LiF (0.8 nm)/Al (100 nm) was fabricated. Among the white polymers, PF-Ir(ppy)2(pytzph)5-Ir(piq)2(pytzph)5 exhibited excellent electroluminescent properties with a Commission Internationale Ed I'eclairage (CIE) coordinate of (0.32, 0.34) and a maximum luminous efficiency of 11.49 cd/A.