title: Nanocrystal skins with exciton funneling for photosensing.
abstract: Highly photosensitive nanocrystal (NC) skins based on exciton funneling are proposed and demonstrated using a graded bandgap profile across which no external bias is applied in operation for light-sensing. Four types of gradient NC skin devices (GNS) made of NC monolayers of distinct sizes with photovoltage readout are fabricated and comparatively studied. In all structures, polyelectrolyte polymers separating CdTe NC monolayers set the interparticle distances between the monolayers of ligand-free NCs to <1 nm. In this photosensitive GNS platform, excitons funnel along the gradually decreasing bandgap gradient of cascaded NC monolayers, and are finally captured by the NC monolayer with the smallest bandgap interfacing the metal electrode. Time-resolved measurements of the cascaded NC skins are conducted at the donor and acceptor wavelengths, and the exciton transfer process is confirmed in these active structures. These findings are expected to enable large-area GNS-based photosensing with highly efficient full-spectrum conversion.
authors.affiliation: UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering and Department of Physics, Bilkent University, Ankara, 06800, Turkey.
authors.forename: Shahab
authors.initials: S
authors.lastname: Akhavan
authors.forename: Ahmet Fatih
authors.initials: AF
authors.lastname: Cihan
authors.forename: Berkay
authors.initials: B
authors.lastname: Bozok
authors.forename: Hilmi Volkan
authors.initials: HV
authors.lastname: Demir
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D005453:Fluorescence; D008027:Light; D008163:Luminescent Measurements / Q000295:instrumentation / Q000379:methods; D008422:Materials Testing; D008567:Membranes, Artificial; D053758:Nanoparticles / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D045663:Quantum Dots / Q000737:chemistry*
chemical_list: D008567:Membranes, Artificial; D009930:Organic Chemicals; C057718:6-(Dimethylamino)-2-((1E,3E)-4-(4-(dimethylamino)phenyl)-1,3-butadien-1-yl)-1-ethylquinolinium perchlorate
keywords: exciton funneling; light sensing; nanocrystalline materials; quantum dots; self-assembled monolayers