(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.