Functional Templates for Hybrid Materials with Orthogonal Functionality

We demonstrate an integrated approach to prepare a nanostructured, multifunctional material with mutually exclusive, orthogonal properties. The hybrid material was obtained within a single step via self-assembly in solution. It consists of TiO2 as a functional metal oxide and an amphiphilic block copolymer, poly(ethylene oxide)-b-poly(triphenylamine) (PEO-PTPA). Within the materials' synthesis, the block copolymer not only acts as a templating agent but also adds an electronic functionality to the resulting hybrid material. During the synthesis, a variety of self-assembled morphologies, ranging from spheres to wires, can be created. The obtained morphology depends on the weight fraction of the polymer, solvent, TiO2, and acid (HNO3). When films on silicon wafers are studied with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), a ternary phase diagram could be mapped, whereas the crystallinity of TiO2 could be proved by high-resolution TEM. Different morphologies of this self-assembled hybrid material were tested for solar cell application. Even for devices with layer thicknesses of the active material below 10 nm, power conversion efficiencies up to 0.15% at 1 sun and 1.5 AM were observed.