Malang, M. P. K.2024-03-122024-03-122023Malang, M. P. K. (2023). Dft and td-dft studies of d-π-a organic dye molecules with different spacers for highly efficient reliable dye sensitized solar cells (DSSCS), (Master's Dissertation) The University of Dodoma.https://repository.udom.ac.tz/handle/20.500.12661/4269Dye-sensitized solar cells (DSSCs) have sparked the interest of photovoltaic researchers due to their promising performance, low cost, and simple production procedure. In this study, a series of six D-π-A Organic dye molecules were design by using different π-spacers. The aim of this study was to utilize computational quantum simulations to investigate the molecular structure, absorption spectra, optical, electronic and photophysical properties of D-π-A organic dye molecules using DFT and TD-DFT computational methods. The , , energy gap ( ) and dipole moment for all dyes have been determined and discussed. The obtained results for excitation energies and the HOMO/LUMO energy level, shows an improvement in electron injection and dye regeneration processes. Furthermore, the energy gap, open-circuit voltage ( ), electron injection free energy ( ), light harvesting efficiency (LHE), and absorption spectra of all dyes were examined and indicate some improvement. The results show that D4 dye molecules have the smallest energy gap (1.505-1.709 eV and 1.396-1.545 eV for gas and solvent phases). Light harvesting efficiency was estimated, and this parameter depend on oscillator strength of dye molecules. The results suggested that D5 dye have the higher LHE (0.933 and 0.981 eV respectively) than other compounds. Therefore, the results of these dyes suggested that D4 and D5 dyes molecules are favorable candidates for DSSCs applications. The study of structural, electronics and optical properties for these compound could aid in the development of more efficient sensitizers for solar cells.enThesis