A rational design of high efficient and low-cost dye sensitizer with exceptional absorptions: Computational study of cyanidin based organic sensitizer

[Display omitted] •Natural dye based metal free dyes are proposed for DSSC via DFT/TDDFT calculations.•Proposed dyes consist of cyanidin as donor, cyanoacrylic acid as acceptor and thieno [3, 2-b] thiophene as π-spacer.•The absorption spectra of new dyes have shown a more redshift than existing dyes, up to near IR of 2500 nm and the absorption bands are more intense in the visible region.•HOMOs are localized over cyanidin, and LUMOs over the thieno thiophene cyanoacrylic.•DFT/TDDFT results revealing all sensitizers enhanced their sensitizing abilities. We have computationally designed and characterized a series of new organic D−π−A architected dyes that have originated from cyanidin, which is vastly available in nature, for effective sensitization of DSSCs with absorption spectra extending up to near infrared region. Cyanidin acts as the donor group while cyanoacrylic acid and thieno [3, 2-b] thiophene are employed as the acceptor and π-spacer, respectively. Sensitization performance, depending on the substituted position of the π-spacer-acceptor (π-A) combination on cyanidin molecule, is examined by the results of density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The calculated data of free energy change driving force (ΔGinject), electron regeneration driving force (ΔGregen), open circuit potential eVOC and light harvesting efficiency (LHE) suggest two preferred substitutions of π-A combination to cyanidin molecule that leads to an efficient DSSC. At LUMO the designed sensitizers have denser electron cloud towards acceptor group that leads to an efficient electron injection process. All π-A substitutions resulted a broader absorption spectrum with a redshift up to 2500 nm which is a significant improvement compared to the vast majority of reported sensitizers.