A block copolymer of crosslinkable polythiophene and removable poly(ethylene oxide) for preparing heterostructures of organic semiconductors

We prepared a block copolymer composed of polythiophene (PT) with cinnamate groups and poly(ethylene oxide) (PEO), which are connected through a cleavable acetal bond, aiming at constructing donor/acceptor heterostructures through post deposition of acceptor molecules into donor template networks. The block copolymer films showed phase-separated structures with domain sizes of 10–100 nm. Irradiation with UV light afforded crosslinked films through [2+2] cyclodimerization of cinnamate groups. Then, PEO was removed by acidic cleavage of the acetal bond, yielding PT template networks. Taking advantage of the insoluble networks, a fullerene derivative was deposited into the PT templates through a spin-coating process to form donor/acceptor heterostructures. The introduction of the fullerene derivative was confirmed by UV-Vis absorption and fluorescence spectroscopy. This strategy of depositing acceptor molecules into donor template networks, instead of spin-coating from donor/acceptor blend solutions, could be applied to improve the phase-separated structures and power conversion efficiencies of polymer solar cells.