Highly emissive fluorene and thiophene based π-conjugated A-alt-B copolymers: Synthesis, characterization and electroluminescence properties

Highly soluble and emissive fluorene and thiophene based A-alt-B type π-conjugated polymers, P1 and P2 have been successfully synthesized through Pd(0)-catalyzed Suzuki coupling polymerization by varying alkyl substitution at 3-position of thiophene. The synthesized cyan-emissive fluorene based π-conjugated polymers have been unambiguously characterized by various spectroscopic tools such as FTIR, multinuclear NMR as well as tetradetector GPC having molecular weight (M_n) 18.2 and 20.8 kDa with the polydispersity indices of 1.32 and 1.35 respectively. The detailed thermal, electrochemical, photophysical and electroluminescence properties of the polymers have been investigated. The highly emissive nature of the synthesized polymers even in solid state prompted us to explore its application as active materials in organic light emitting diodes (OLEDs). The electroluminescence properties of the obtained materials are studied by fabricated the device using the configuration ITO/PEDOT:PSS (50 nm)/P1-P2 (80 nm)/BCP (40 nm)/Al (100 nm). P1 and P2 exhibit bright cyan electroluminescence with CIE of (0.19, 0.29) and (0.21, 0.31) respectively with relatively lower onset voltage of 4 V.