Synthesis and properties of new low band gap semiconducting polymers.

ABSTRACT

Low band gap organic semiconducting polymers were prepared as p-type donors for organic photovoltaic devices. A novel dibrominated monomer composed of phenothiazine, thiophene, and benzothiadiazole (DPDTBT) was synthesized as a low band gap core block. DPDTBT was copolymerized with three different boronic esters of dithiophene, fluorene, and phenothiazine by the Suzuki coupling polycondensation reaction. The band gap energies of the synthesized polymers ranged between 2.05 and 2.11 eV, depending on the polymer structure. Bulk heterojunction solar cells fabricated using the polymers and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) as an acceptor were characterized. The best power conversion efficiency obtained from the fabricated devices under simulated AM 1.5 G solar irradiation of 100 mW/cm2 was 0.46%.