4,5-Diazafluorene ligands and their ruthenium(II) complexes with boronic acid and catechol anchoring groups: design, synthesis and dye-sensitized solar cell applications

Abstract

Design, synthesis, characterization, and investigation of photovoltaic properties of 4,5-diazafluorene derived diimine ligands (C2, C3) and their ruthenium(II) complexes are reported. FT-IR, ¹H NMR, ¹³C NMR, and mass spectroscopic methods were used to elucidate the structures of these compounds. The effect of the number and nature of anchoring groups attached to these ligands and complexes as sensitizers were evaluated for optical properties and photovoltaic performance in dye-sensitized solar cells (DSSCs). The sensitizers bearing catechol show higher power conversion efficiency (PCE) than the dyes with boronic acid due to better binding of the catechol anchoring group on the TiO₂ surface. Among these sensitizers, DSSC based on [Ru(C2)₂(NCS)₂](PF₆)₂ having two catechol anchoring groups gives the best PCE of 2.83%, with J_sc = 6.40 mA cm⁻², V_oc = 0.632 V and FF = 0.70 in the presence of chenodeoxycholic acid (CDCA) as the coadsorbent, which is attributed to broader spectral response and efficient electron injection. These results suggest that dyes bearing two catechol anchoring groups are promising for efficient DSSCs.

Graphical Abstract

Keywords:

• 4,5-Diazafluorene
• ruthenium(II) complexes
• photosensitizer
• photovoltaic
• dye-sensitized solar cells

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) Ph.D. Scholarship Program in Priority Areas (2211/C) and Council of Higher Education (YOK) Ph.D. Scholarship Program (100/2000).