Cutting-edge dyes for p-type dye-sensitized solar cells: a theoretical study of 1,8-naphthalene imide derivatives

We report a theoretical investigation of the designed 1,8-naphthalene imide-based dyes for application in p-type dye-sensitized solar cells (p-DSSCs). The designed dyes are metal-free organic molecules combined with a carbazole donor, a naphthalene imide acceptor, and a cyanocarboxylic acid anchoring group. Different linkers, including benzothiadiazole, phenyl, furan, and thiophene, were introduced to modify their properties. The p-DSSCs were theoretically evaluated with five various p-type semiconductors (CuO, Cu₂O, CuGaO₂, CuCrO₂, and CuAlO₂) and six various electrolytes based on cobalt and copper complexes. Computational analysis was performed by means of Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT). For all designed dye, the HOMO levels were sited below the valence band of the semiconductors, while the LUMO levels were located above the redox potential of the electrolytes. This alignment confirms hole injection and dye regeneration. The results show that the dyes, especially those with benzothiadiazole and phenyl linkers, are promising dyes for improving p-DSSC efficiency through enhanced light harvesting, effective charge separation, and reduced recombination losses. These findings contribute valuable insights into the design of high-performance p-type photosensitizers for tandem DSSC applications.