Theoretical Investigation of Azobenzene-Based Photochromic Dyes for Dye-Sensitized Solar Cells.

Two donor-π-spacer-acceptor (D-π-A) organic dyes were designed as photochromic dyes with the same π-spacer and acceptor but different donors, based on their electron-donating strength. Various structural, electronic, and optical properties, chemical reactivity parameters, and certain crucial factors that affect short-circuit current density ( J _sc ) and open circuit voltage ( V _oc ) were investigated computationally using density functional theory and time-dependent density functional theory. The trans - cis isomerization of these azobenzene-based dyes and its effect on their properties was studied in detail. Furthermore, the dye-(TiO ₂ ) ₉ anatase nanoparticle system was simulated to understand the electronic structure of the interface. Based on the results, we justified how the trans - cis isomerization and different donor groups influence the physical properties as well as the photovoltaic performance of the resultant dye-sensitized solar cells (DSSCs). These theoretical calculations can be used for the rapid screening of promising dyes and their optimization for photochromic DSSCs.