Synthesis and photovoltaic properties of a seriesof bulk heterojunction solar cells based oninterchain-linked conjugated polymers

摘要

We have used Suzuki coupling to synthesize a series of maleimide–thiophene copolymers presenting pendent 2-hydroxyethyland 6-hydroxyhexyl units. The maleimide–thiophene copolymers containing different contents of OH groups were then reactedwith 3,30-dimethoxy-4,40-biphenylene diisocyanate (DMBPI) in solution to form the interchain-linked polymers. The interchainlinkedpolymers exhibited excellent solubility in organic solvents. The average molecular weight and thermal stability of thecopolymers increased after interchain linking with DMBPI. The wavelengths of maximum absorption of the interchain-linkedcopolymers were red-shifted relative to those of the corresponding side-chain copolymers. The energy level of the lowestunoccupied molecular orbitals and highest occupied molecular orbitals decreased after the copolymers had undergoneinterchain linking with DMBPI. We fabricated polymer solar cells (PSCs) from blends of the interchain-linked copolymers and[6,6]-phenyl-C61-butyric acid methyl ester. The photovoltaic performances of the PSCs incorporating the interchain-linkedcopolymers were superior to those of the corresponding PSCs based on the OH-presenting copolymers.