Synthesis, photophysical, electrochemical, and quantum chemical investigations of a novel phenothiazine-derived organic dye for high efficiency dye-sensitized solar cells

Abstract In the present work, we report the first-time synthesis of 3-(2-cyanopropanoic acid)-N-propyl-10H-phenothiazine, a novel phenothiazine-based dye designed to develop photovoltaic performance. The molecular structure has been confirmed by FT-IR, ¹ H/ ¹³ C NMR, and HR-MS, and its optimized geometry and spectroscopic properties have been investigated by using density functional theory. The dye possesses a non-planar butterfly-shaped configuration, which suppresses aggregation, while its electron-rich N and S atoms enhance donor capability and light-harvesting efficiency. The dye exhibited strong absorption at 437 nm, with a HOMO of −5.21 eV and LUMO of −3 eV. Theoretical calculations indicate a favorable Δ G ^inj of −0.936 eV and light-harvesting efficiency of 73.7%. When utilized as a sensitizer, the device achieved a short-circuit current density ( J _sc ) of 21.17 mA cm ⁻² , open-circuit voltage ( V _oc ) of 0.71 V, fill factor ( FF ) of 0.65, and power conversion efficiency ( PCE ) of 9.75%, outperforming the benchmark N719 (7.09%). These findings demonstrate that this newly synthesized phenothiazine derivative dye is a promising candidate for next-generation dye-sensitized solar cells.