This is an on-going project in collaboration with Dr. Reynolds group at UF. In this project, platinum acetylide type polymers are utilized as an active layer material in bulk-heterojunction photovoltaic devices. Three key factors in photovoltaic devices are: 1) efficiency of photon absorption, 2) efficiency of photo-induced charge separation, and 3) efficiency of exciton diffusion. The first factor can be improved by choosing a right chromophore to match the solar spectrum. Incorporation of platinum atom in the polymer backbone enhances the second factor by longer lifetime of triplet excited state of the donor. Spin-orbit coupling induces by heavy atom effect of platinum produces large population of triplet state excited state. The third factor can be improved by incorporation of bulk hetero-junction in the active layer. In contrast to “layered type photovoltaic devices”, the active layer of bulk-heterojunction devices is a blend of acceptors and donors. Such design improves the efficiency of devices significantly by increasing the efficiency of exciton diffusion in the material. As expected, improved efficiency of the photovoltaic device was observed with devices constructed with p-PtTh/PCBM blend. To obtain better match with the solar spectrum, devices with p-PtBTD-Th/PCBM and p-PtBTD-EDOT/PCBM were constructed. Although much better efficiencies were obtained, the charge transfer mechanism was found to be through singlet excited state of the donor instead of the triplet state. 

Ref: (1) Guo, F.; Kim, Y.-G.; Reynolds, J. R.; Schanze, K. S. "Platinum–acetylide polymer based solar cells: involvement of the triplet state for energy conversion." Chem. Commun. 2006, 1887-1889.

(2) Guo, F.; Ogawa, K.; Kim, Y.-G.; Danilov, E. O.; Castellano, F. N.; Reynolds. J. R.; Schanze, K. S. "A fulleropyrrolidine end-capped platinum-acetylide triad: the mechanism of photoinduced charge transfer in organometallic photovoltaic cells." Phys. Chem. Chem. Phys. 2007, 9, 2724-2734.