Photoinduced Charge Transport Dynamics under the Influence of an Electric Field on Dye-Sensitized Solar Cells with a D−π–A Structure

First-principle studies within the formalism of density functional theory have been performed to investigate the photoinduced charge transfer in Zn-porphyrin based dye-sensitized solar cells (DSSCs). The FSQ101, SM315-based Zn-porphyrin dye has been chosen as a valuable platform to explore the interplay between the direction and strength of the applied electric field and photovoltaic performance. The model system has an electron-rich donor group, a π-linker as a bridge, and a cyanoacrylic acid as an acceptor group. All simulations have been conducted with respect to the TiO2 semiconductor and I3−/I– electrolyte. The applied electric field (−30 × 10–5 au to 30 × 10–5 au) mimics the inner electric field generated in practice in solar cell devices. Static and time-dependent density functional calculations provide a comprehensive analysis of the dynamics of photovoltaic properties in relation to the applied field strength. The results demonstrate that an electric field can effectively modulate the photoelectric characteristics and enhance the charge transfer process of the dye molecule. When the field is along the positive X-axis, dye exhibits a narrow band gap, well-defined charge separated states, larger λmax, and broader and red-shifted bands toward the near-infrared region. The analysis of frontier orbitals, absorption spectra, chemical reactivity parameters, nonlinear optical properties, and photovoltaic properties (LHE, JSC, VOC, Edye*, ΔGinj, ΔGreg, EBE, Vda, λr, k) provides molecular level understanding of underlying processes such as photoinduced electron injection, generation of electron–hole pair, and intramolecular charge transfer (ICT) that are crucial in deciding the efficiency of the DSSCs. The charge density difference plots were plotted at different field strengths to classify the electronic transitions as ICT or local excited (LE) transitions. The study substantiates the improved performance of the designed DSSC when subjected to a positive field compared to negative and field-free conditions.