Nonradiative Energy Transfer between Porphyrin and Copolymer in Films Processed by Organic Solvent and Water-Dispersible Nanoparticles with Photovoltaic Applications

In organic photovoltaic (OPV) devices, one way to increase light harvesting is to combine materials with complementary absorptions. However, the physical properties behind this process, such as Förster resonance energy transfer (FRET), remain elusive. A mixture of the metalloporphyrin Zn­(5BrTTP) and the donor–acceptor copolymer PSiF-DBT in films processed by organic solvent and water-soluble nanoparticles was investigated, and the energy-transfer rate was correlated to the bilayer of an OPV device with a fullerene derivative (C₇₀). Using steady-state and time-resolved emission studies, the FRET from the porphyrin to the copolymer was observed and found to be highest in the film processed by organic-solvent treatment at 100 °C. The devices processed by organic solvents showed superior performance to blended materials when treated at 100 °C, increasing the current without reducing open-circuit voltage. In nanoparticle systems, we observed that, with a smaller distance between the materials, higher FRET is performed. The device’s performance showed higher current as the materials were closer together. To go beyond materials with complementary absorption, the optimization of energy transfer between them might be a promising way to increase charge generation in photovoltaic devices with different morphologies