Cyclometalated platinum polymers: Synthesis, photophysics, and organic electronics applications

Conjugated polymer photovoltaics have the potential to provide inexpensive, lightweight solar panels for a new generation of energy technology. A primary limiting factor to the performance of semiconducting polymers is the short (5-10 nm) exciton diffusion length. Materials incorporating transition metals show significantly increased intersystem crossing yields as a result of the heavy atom effect, making such materials attractive for improved photovoltaic applications. We present the synthesis, photophysical characterization, and photovoltaic properties of platinum-containing conjugated polymers wherein the platinum atom is attached peripherally via a new CN ligand. By using this mode of attachment the platinum atom remains involved in excited state molecular orbitals but does not inhibit conjugation along the polymer backbone. Our results relate the delocalization of the initially formed exciton to the intersystem crossing efficiency and indicate design principles for the further development of conjugated polymers with significant triplet yields useful for solid state photovoltaic devices.