Effects of a side chain sequence on surface segregation of regioregular poly(3-alkylthiophene) and interfacial modification of bilayer organic photovoltaic devices

摘要

A regioregular poly(3-alkylthiophene) with a statistical sequence of alkyl/semifluoroalkyl side chains (stat-P3DDFT) was synthesized through the copolymerization of mixed monomers. The surface segregation behavior was compared with the corresponding alternating copolymer (a/f-P3DDFT) that forms highly ordered dipole layers by surface segregation. X-ray and ultraviolet photoelectron spectroscopies of the polymer films revealed that a/t-P3DDFT formed a much more ordered surface segregated monolayer than did staf-P3DDFT, indicating the importance of the alternating sequence of the side chains. When sfat-P3DDFT was inserted into the donor/acceptor interfaces in bilayer organic photovoltaic devices, the short circuit current and the open circuit voltages of the devices were related to the disordered interface structures of sfat-P3DDFT.