A comprehensive investigation of donor-acceptor anthraquinone derivatives as versatile and efficient photosensitisers for dye-sensitised solar cells

• Anthraquinone donor–acceptor-π-anchor (D-A-π-A) photosensitizers were synthesized. • They show enhanced efficiencies relative to previous anthraquinone photosenstizers. • PCE above 1.1%, significantly higher than previous values below 0.2% were obtained. A new metal-free anthraquinone donor–acceptor-π-anchor (D-A-π-A) design was developed using unsymmetrically substituted anthraquinone (ATQ) derivatives functionalized with bromine (Br), diphenylamine (DPA), indoline (Ind), BrATQBzOH , DPAATQBzOH , and IndATQBzOH . The synthesised compounds, functionalized with an anchor group (ethynylbenzoic acid), have been evaluated in practical dye-sensitised solar cell (DSSC) devices to improve electron injection efficiency. Their properties and applicability were analysed and rationalised based on their energy levels and parameters derived from the current–voltage (I-V) curve analysis in real devices. Femtosecond transient absorption measurements of the sensitiser IndATQBzOH with TiO 2 revealed distinct excited state dynamics and charge transfer properties, highlighting the influence of the semiconductor interface. In addition, Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) electronic quantum calculations were performed, which revealed that the new anthraquinone-based dyes exhibit optimal coplanarity for efficient electron transfer, with their LUMO and HOMO energy levels facilitating electron injection into TiO 2 . In contrast to the low efficiencies found for previously studied anthraquinone derivatives, with maximum photocurrent efficiencies (PCE) below 0.2%, 9,10-anthraquinone derivatives were used as acceptors attached to suitable donors (DPA or Ind), yielding PCE above 1%.