Multifunctional materials for OFETs, LEFETs and NIR PLEDs

Abstract

A family of phthalimide–thiophene copolymers with linear and branched alkyl chains attached to the imide nitrogen have been synthesized. Their optical and electronic properties were investigated along with their applications in OFETs and LEFETs. The phthalimide–thiophene copolymer having a C₁₆ straight alkyl chain on the phthalimide yielded the highest mobilities and PLQE with mobilities of 1 × 10⁻³ cm² V⁻¹ s⁻¹ for holes and 1 × 10⁻² cm² V⁻¹ s⁻¹ for electrons with a PLQE of ∼28% in the solid state. Since these polymers are ambipolar and emissive, they have proven to be useful for applications as a host material for NIR PLEDs. In this study a 1% loading of NIR emitting DAD segments based on bisthienyl(thiadiazoloquinoxaline) or bisthienyl(benzotriazolothiadiazole) were incorporated into the phthalimide–thiophene polymerization. Using the branched CH(C₈H₁₇)₂ alkyl chain on the host phthalimide–thiophene copolymer combined with the bisthienyl(benzotriazolothiadiazole) emitter resulted in the most efficient (emission maximum ≥ 850 nm) single layer NIR-emitting PLED to date with an EQE of 0.27% emitting at 885 nm.