Synthesis of 2H-benzotriazole based donor-acceptor polymers bearing carbazole derivative as pendant groups: Optical, electronical and photovoltaic properties

Four 2H-benzotriazole based D-A polymers bearing carbazole derivative as pendant groups and fluorene or thiophene as donor units (Pl-P4) were designed and synthesized. These polymers combine good thermal stability and excellent solubility in common organic solvents. Spectroscopic measurements carried out for P1, P2 and P3 indicate that polymer backbone induces effective the quenching of the 3,6-di(thiophen-2-y1)-9H-carbazole (CT) fluorescence, implying an intramolecular Forster Resonance Energy Transfer (FRET) process. Preliminary investigations on the photovoltaic multiheterojunction devices based on Pl-P4 showed power conversion efficiencies (PCEs) of up to 1.7 % for P1 and P2 and close to 2.0 % for P3. This means that the polymer/pi-conjugated pendant units structure is a promising alternative to improve the performance of organic solar cells.