Exponential optical absorption edge in PbS quantum dot-ligand systems on single crystal rutile-TiO2 revealed by photoacoustic and absorbance spectroscopies

Abstract The photovoltaic properties of quantum dot (QD) sensitized solar cells (QDSCs) depend significantly on the surface modification applied to QDs and nanostructured interface between electrode surface. In development QDSCs with spatially ordered QD arrays, linking molecular ligands (QD-ligands) can lead realization novel QDSCs. ligand shell around mediates electron energy transfer processes that underpin their use in QDSC applications. dependence interparticle distance (QD spacing) also be evaluated by applying different sizes ligands. present study focuses specific attention exponential optical absorption edge (often termed Urbach tail) PbS QD-ligand systems spacing adsorbed rutile-TiO2 (R-TiO2) substrates crystal orientations. It is essential accurately characterize QD-ligands surfaces orientations, not only for scientific studies, but further optimize growth conditions order design fabricate advanced Photoacoustic (PA) conventional absorbance (Abs) spectroscopies were determine nonradiative relaxation properties. There a discrepancy PA Abs spectra especially tail region. As states are related absorbed photon lost form heat generated relaxation, therefore characterization important Characterization combined showed characteristics strongly orientation R-TiO2 substrate, spacing, free change.