Polythiophenylpyrazoline containing fluorene and benzothiadiazole moieties as blue and white light emitting materials

Abstract

Low band gap polythiophenylpyrazoline containing fluorene and benzothiadiazole moieties were synthesized and characterized in combination with high donor content (PFPF) and high acceptor content (PBPF). The PBPF displays broad emission as white light dual fluorescence via locally excited state and charge transfer state as single polymer, while PFPF exhibits blue light emission. This dual emission can be utilized to reduce problem with forster energy transfer from high energy to low energy excited state. The polymers are soluble in many organic solvents thus solvatochromism explored in nonpolar to polar solvents. The energy state of polymers were compared with small molecule namely, 1,3-diphenyl-5-(9-phenanthrenyl)-2-pyrazoline (DPPhP) under similar condition. It is observed that LUMO level is brought down and imparts improved electron injection and better transport ability. This approach yield a toolbox of molecules that can be used to construct π-conjugated polymers with a variety of composition lead to explore better organic light emitting diode performance.