(D–π–A)₂–π–D–A type ferrocenyl bisthiazole linked triphenylamine based molecular systems for DSSC: synthesis, experimental and theoretical performance studies

Abstract

We have designed and synthesized ferrocenyl (donor) bisthiazole linked triphenylamine (donor) based donor-π-acceptor-π-donor-acceptor (D-π-A)₂-π-D-A type dyes D1 and D2 by using Pd-catalyzed Sonogashira cross-coupling and Knoevenagel condensation reactions. Their photophysical, electrochemical and computational studies reveal strong donor-acceptor interaction. Dye sensitized solar cells (DSSCs) based on D1 and D2 exhibit power conversion efficiencies (PCE) of 6.33% and 5.03%, respectively. The higher PCE value of the D1 based DSSC is attributed to its enhanced short-circuit current (J_sc) and open-circuit current (V_oc) and fill factor (FF) values because of the strong binding of the anchoring cyanoacrylic acid with the TiO₂ surface as compared to the dicyanovinyl unit in D2. Time dependent density functional theory (TD-DFT) calculations at B3LYP level on dyes D1 and D2 were performed, which reveal that both dyes show HOMO-1 → LUMO as a major transition. Computational photovoltaic calculations also reveal that dye D1 has better electron injection (ΔG_inject) from E_LUMO to the conduction band (CB) of TiO₂ as compared to dye D2, which is in good agreement with experimental results.