Nanostructured Photovoltaic Devices from Thermally-Reactive π-Conjugated Polymer Blends

A facile method for preparing nano- and microstructured π-conjugated polymers (πCPs) from polymers bearing thermally cleavable solubilizing groups for the application of organic photovoltaic cells is described. Solutions of thermally reactive poly[3-(2-(2-tetrahydropyranyloxy)ethyl)thiophene)] (PTHPET), poly(methylmethacrylate) (PMMA), and camphorsulfonic acid were spin-cast to yield nano- and micro- phase segregated thin films, ∼100 nm thick. A thermally induced, acid-catalyzed, solid-phase reaction, in which the tetrahydropyran group is eliminated, renders the conjugated polymer insoluble. Subsequent removal of PMMA by dissolution affords retention of the conjugated polymer in the form of nano/microarchitectures. This strategy proved useful in the fabrication of controlled nano/microscale structures for organic photovoltaic cells devices, wherein insoluble, nanostructured De-PTHPET served as a donor layer and a spin-cast solution of PCBM accessed the recesses of the film to serve as the electron acceptor layer. The properties of nanopatterned PV devices are compared to conventional bilayer, and bulk heterojunction devices. The nanostructured, donor−acceptor films provided an advantage over molecularly blended films in that potential isolation of electron acceptor in the donor film is decreased, and vice versa, mitigating charge trapping, and providing improved device efficiency.