A computational approach on engineering short spacer for carbazole-based dyes for dye-sensitized solar cells

Donor-n-linker-acceptor (D-n-A) push-pull dye molecules are most common in dye-sensitized solar cells (DSSCs) applications. Selection of dye molecules for DSSCs is based on their ability to absorb light in the visible spectrum. This can be done more efficiently by positioning the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) with respect to the conduction band of the semiconductor and the redox potential of the electrolyte, respectively. The photocurrent is manipulated by the extent of light absorption, planarity of the n-linker for efficient intramolecular charge transfer (ICT), oxidized dye reorganization energy (?) and dye regeneration driving force (Delta Greg). In a quest of achieving panchromatic absorption up to near-IR region, mostly electron-rich chromophores and their oligo form were used in the n-segment, but this approach led to poor ICT. In this computational analysis, we have explored the effect of electron-withdrawing (cyano (-CN)) and donating groups (methoxy (-OMe)) in three different n-segment length to understand the carbazole dyes' suitability for DSSCs using onset wavelength (lambda onset), ?, ICT and Delta Greg as the figure-of-merits.