Novel regioregular polythiophenes containing side-chain porphyrin groups for polymeric photovoltaic cells

• Preparation of new porphyrin-functionalized regioregular thiophene copolymers.
• Copolymers with variable porphyrin contents, very soluble and easily filmable.
• Optical, electrochemical and photovoltaic properties were investigated.
• Bulk heterojunction cells based on the copolymers were prepared.
• Fabrication of cells with good reproducibility of performances.

The paper presents a new strategy for the preparation of porphyrin-functionalized head-to-tail regioregular thiophene copolymers using a simple and effective post polymerization functionalization (PPF) procedure based on the synthesis of a regioregular and soluble polythiophene precursor followed by subsequent reaction with a suitably functionalized porphyrin derivative. Thus, thiophene copolymers poly[3-(6-bromohexyl)thiophene-co-(3-[5-(4-phenoxy)-10,15,20-triphenylporphyrinyl] hexylthiophene)]s at different porphyrin chromophore contents were prepared, obtaining, in all cases, very soluble and easily filmable derivatives. Their thermal, optical and electrochemical properties were determined and their performances as the active layer in bulk heterojunction solar cells tested.