A molecular view on dye-sensitized solar cell interfaces with in situ nearfield Raman spectromicroscopy

• Applicant: Professorin Dr. Katrin F. Domke
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2012 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 219933149

• Final Report Year: 2018

Final Report Abstract

• We implemented a novel TERS setup with which TER spectra from electrified solid/liquid interfaces can be recorded. • We recorded TER spectra from a monolayer of resonant MGITC dye adsorbed at a Au(111) single crystal in water with Raman enhancements in the order of 10^5 . • We recorded TER spectra from a monolayer of nonresonant PhS adsorbed at Au(111) single crystal in water. • We studied the potential-dependent EC-TER response from a monolayer of nonresonant adenine at Au(111) in sulfuric acid electrolyte. The observed band intensity decrease with increasing potential is reversible and can be, at first approximation, attributed to adsorbate reorientation upon (dis)charging of the Au electrode. • We found that PbS sensitizers prepared under conventionally employed SSC device fabrication conditions show a significant contribution of PbO. In the presence of O2 and moderate laser power in the order of a few mW, PbS is oxidized to PbSO4 . PbS oxidation is accompanied by a change in band gap as evident form scanning tunneling spectroscopy results. • We systematically investigated the effect of hydrogenaion of the titania band gap. Increased H2 annealing of TiO2 shifts the titania conduction band towards less negative energies. • We found a simple fabrication protocol to make MAPbI3 perovskite needles of varying size. The protocol allows to tune the needle width over one order of magnitude between ca. 200 and 2000 nm. • We attribute the observed blue shift in photoluminescence with decreasing MAPbI3 needle size to Pb2+ surface-state induced geometric rearrangement in the perovskite crystal lattice. We were surprised to learn that TER spectra can be recorded from solid/liquid interfaces with a proper side-illumination implementation without aberration correction of the far-field focus. - Our instrument was found to be not sensitive and specific enough to observe TER scattering from N3 and N719 sensitizer dyes on TiO2 substrates on top of the far-field substrate Raman signal and dye luminescence background.

Publications

• Index mismatch aberration correction over long working distances using spatial light modulation. Applied Optics 2012, 51, 8034-8040
  Gjonaj, Bergin; Johnson, Patrick; Bonn, Mischa & Domke, Katrin F.
  
• ”A versatile side-illumination geometry for tip-enhanced Raman spectroscopy at solid/liquid interfaces” Analytical Chemistry 2016, 88, 7108-7114
  Martín Sabanés, Natalia; Driessen, Leonie M. A. & Domke, Katrin F.
  
• ”Electrochemical TERS elucidates potential-induced molecular reorientation of adenine/Au(111)” Angewandte Chemie International Edition 2017, 56, 9796-9801
  Martín Sabanés, Natalia; Ohto, Tatsuhiko; Andrienko, Denis; Nagata, Yuki & Domke, Katrin F.
  
• ”Raman under water - Nonlinear and nearfield approaches to elucidate nanoscale electrochemistry” ChemElectroChem 2017, 4, 1814-1823
  Martín Sabanés, Natalia & Domke, Katrin F.
  
• ”The effect of STM parameters on tip-enhanced Raman spectra” Faraday Discussions 2017, 205, 233-243
  Sabanés, Natalia Martín; Elizabeth, Amala; Pfisterer, Jonas H. K. & Domke, Katrin F.
  
• ”The SERS signature of PbS quantum dot oxidation” Vibrational Spectroscopy 2017, 91, 157-162
  Stadelmann, Kathrin; Elizabeth, Amala; Martín Sabanés, Natalia & Domke, Katrin F.
  
• ”Unfolding the versatile potential of EC-TERS for electrocatalysis” Current Opinion in Electrochemistry 2018 8, 96-102
  Pfisterer, Jonas H.K. & Domke, Katrin F.