Manipulation of 2-[2-(10H-phenothiazin-3-yl)thiophen-3-yl]-10H-phenothiazine Based D-A-π -A Dyes for Effective Tuning of Optoelectronic Properties and Intramolecular Charge Transfer in Dye Sensitized Solar Cells: A DFT/TD-DFT Approach

Due to continuous growing in energy consumption brought on by economic development and population growth around the world, solar energy has emerged as one of the most important sources of renewable energy for human use. In this study, twelve metal-free organic dyes containing 2-[3-(10H-phenothiazin-3-yl)furan-2-yl]-10H-phenothiazine and its analogues as donor units inform of the D-A-π-A structure (PBPD and PTPD) were theoretically studied for application in dye-sensitized solar cells (DSSCs). The structural, electrical, photovoltaic and optical properties of the PBPD and PTDP dyes were carefully examined in relation to the impacts of changing the donor and π-spacer. The PBDP dyes showed band gaps (ΔEg) in the range of 1.75 (PBPD-4) to 2.09 eV (PBPD-3) while ΔEg values for PTPD dyes range from 1.87 eV (PTPD-4) to 2.33 eV (PTPD-3). The estimated open-circuit voltage (Voc) values ranged from 0.79 eV (PTPD-3) to 0.96 eV (PBPD-1 and PBPD-2) while the light gathering efficiency (LHE) values ranged from 0.766 (PTPD-2) to 0.968 (PBPD-6). The HOMO energies, ΔEg values, injection drive force (ΔGinj), reorganization energies (λ total) and coupling constant (|V_RP |) favoured PBPD dyes over PTPD dyes.