a Department of Physics, Jamal Mohamed College (Autonomous) (Affiliated to

Bharathidasan University), Tiruchirappalli-620020, Tamil Nadu, India

^bDepartment of Physics, PSG College of Arts and Science (Autonomous),

Coimbatore-641014, TamilNadu, India

The advancement of cost-effective, highly efficient sensitizers plays a crucial role in the progress of dye-sensitized solar cells (DSSCs). Employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT), a range of metal-free organic dyes with D - π - A configuration, featuring different donor and acceptor groups, have been investigated to enhance the effectiveness of sensitizer dyes. We developed metal-free organic dyes (Ak1-Ak6) with a D - π - A structure through structural modifications of alkannin reference dye. Calculations were conducted to assess the electronic and optical properties, along with key parameters such as short-circuit current density (Jsc) and open-circuit voltage (Voc), including light-harvesting efficiency (LHE), electronic injection-free energy (ΔG inject), and regeneration driving forces (ΔG reg) of the designed dyes. The outcomes of this study offer valuable insights for the design of high- efficiency DSSCs.