Novel pull–push solar switches with a D-π-D-π-A framework of the thiophene core: computed absorbance/fluorescence ability with device parameters.

The new design of 6,6′-di(thiophen-2-yl)-4,4′-bipyrimidine (DTB)-based organic dyes (TCIT1-TCIT6) for dye-sensitized solar cell (DSSC) application was systematically designed by a donor (D), π-linker, and acceptor (A) design to form the D-π-D-π-A structure. The exchange–correlation (XC) as well as long-range corrected (LC) functionals were utilized to represent these dyes in density functional theory (DFT) and time-dependent DFT (TD-DFT) techniques. The TD-CAM-B3LYP approach was perfectly matched the DTB dye. Energy gaps between highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) ranged between 1.73-2.92 eV. Their light-harvesting efficiency (LHE) values ranged between 0.001-0.106 eV with dye TCIT5 with the highest value. The open circuit voltage calculated against the DTB as donor moiety ranged 2.45–3.64 eV with positive values to demonstrate their ON position in their solar devices. All the dyes showed a very short excited-state lifetime ranging between 0.0001-0.0051 ns which showed how easily they can shift from an excited- (fluorescent) to ground-state position. Improved results for DSSCs were provided by the intended dyes in addition to their high horizontal dipole moment (µnormal) and open circuit photovoltage (eVOC). It benefits increased efficiency as a result. The findings of the current theoretical analysis show that all D-π-D-π-A dyes may be suitable sensitizers for DSSC applicability. [ABSTRACT FROM AUTHOR]