Near-Infrared Electroluminescent Conjugated Copolymer: Triphenyalmine-Functionalized Benzothiadiazole-Thiophene System for Circularly Polarized OLEDs.

We present a conjugated copolymer designed as a near-infrared (NIR) emitter for organic light-emitting diodes (NIR-OLEDs). The low bandgap donor-acceptor copolymer, comprising a terthiophene derivative (3T) and benzothiadiazole (BT), is end-capped with bulky triphenyalmine (TPA) groups (3TBT-TPA). Compared with the parent homologue capped with simple phenyl rings, 3TBT-TPA shows enhanced solubility in organic solvents with improved photoluminescence quantum yield thanks to a reduced close packing of chains. 3TBT-TPA, used both as neat emitting layer and blended with fluorene-benzothiadiazole (F8BT) host copolymer in a NIR-OLEDs, shows external quantum efficiency up to 0.58%. Additionally, chiral induction is achieved in the F8BT:3TBT-TPA blend film using a commercial chiral dopant, yielding circularly polarized (CP), photoluminescence (PL) and electroluminescence (EL) in the range 500-800 nm with a maximum dissymmetry factor in the range of 10-2. This is the first example of CP-NIR EL from a conjugated polymer. This work highlights the potential of TPA-capped strategy for low bandgap copolymers for efficient NIR-OLEDs and opens new perspectives in the use of conjugated polymers in NIR photonic applications.