Cyclometalated platinum polymers: Synthesis, photophysical properties, and photovoltaic performance

The synthesis and characterization of platinum-containing conjugated polymers in which the platinum atom is attached to the conjugated backbone via a ĈN ligand is presented. The newly designed platinum-containing monomer can be polymerized under both Stille and Suzuki conditions. The polymers exhibit optical bandgaps between 2.1 and 1.65 eV depending on the choice of comonomer. Triplet exciton formation is detected indirectly by measuring photosensitized emission of singlet oxygen in both solution and in film. The ability of the materials to sensitize formation of singlet oxygen varies both with excitation wavelength and with the change from solution to solid state. This study provides design principles for developing conjugated polymers with significant triplet yields in the solid state. The photovoltaic performance of these polymers was also evaluated in preliminary experiments with power conversion efficiencies as high as 1.3% obtained for a bulk heterojunction cell with PCBM.