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Portrait of Arkady Yartsev. Photo: Kennet Ruona

Arkady Yartsev


Portrait of Arkady Yartsev. Photo: Kennet Ruona

Dye-sensitized solar cells based on Fe N-heterocyclic carbene photosensitizers with improved rod-like push-pull functionality


  • Linnea Lindh
  • Olga Gordivska
  • Samuel Persson
  • Hannes Michaels
  • Hao Fan
  • Pavel Chábera
  • Nils W. Rosemann
  • Arvind Kumar Gupta
  • Iacopo Benesperi
  • Jens Uhlig
  • Om Prakash
  • Esmaeil Sheibani
  • Kasper S. Kjaer
  • Gerrit Boschloo
  • Arkady Yartsev
  • Marina Freitag
  • Reiner Lomoth
  • Petter Persson
  • Kenneth Wärnmark

Summary, in English

A new generation of octahedral iron(ii)-N-heterocyclic carbene (NHC) complexes, employing different tridentate C^N^C ligands, has been designed and synthesized as earth-abundant photosensitizers for dye sensitized solar cells (DSSCs) and related solar energy conversion applications. This work introduces a linearly aligned push-pull design principle that reaches from the ligand having nitrogen-based electron donors, over the Fe(ii) centre, to the ligand having an electron withdrawing carboxylic acid anchor group. A combination of spectroscopy, electrochemistry, and quantum chemical calculations demonstrate the improved molecular excited state properties in terms of a broader absorption spectrum compared to the reference complex, as well as directional charge-transfer displacement of the lowest excited state towards the semiconductor substrate in accordance with the push-pull design. Prototype DSSCs based on one of the new Fe NHC photosensitizers demonstrate a power conversion efficiency exceeding 1% already for a basic DSSC set-up using only the I/I3redox mediator and standard operating conditions, outcompeting the corresponding DSSC based on the homoleptic reference complex. Transient photovoltage measurements confirmed that adding the co-sensitizer chenodeoxycholic acid helped in improving the efficiency by increasing the electron lifetime in TiO2. Time-resolved spectroscopy revealed spectral signatures for successful ultrafast (<100 fs) interfacial electron injection from the heteroleptic dyes to TiO2. However, an ultrafast recombination process results in undesirable fast charge recombination from TiO2back to the oxidized dye, leaving only 5-10% of the initially excited dyes available to contribute to a current in the DSSC. On slower timescales, time-resolved spectroscopy also found that the recombination dynamics (longer than 40 μs) were significantly slower than the regeneration of the oxidized dye by the redox mediator (6-8 μs). Therefore it is the ultrafast recombination down to fs-timescales, between the oxidized dye and the injected electron, that remains as one of the main bottlenecks to be targeted for achieving further improved solar energy conversion efficiencies in future work.


  • NanoLund: Center for Nanoscience
  • eSSENCE: The e-Science Collaboration
  • Chemical Physics
  • Computational Chemistry
  • Centre for Analysis and Synthesis

Publishing year







Chemical Science





Document type

Journal article


Royal Society of Chemistry


  • Physical Chemistry
  • Atom and Molecular Physics and Optics




  • ISSN: 2041-6520