Nanocrystal skins with exciton funneling for photosensing
Demir, H. V.
Please cite this item using this persistent URLhttp://hdl.handle.net/11693/25814
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. Photosensitive gradient nanocrystal skins rely on accumulating dissociated excitons after photogenerating and funneling. Excitons funnel along a gradually decreasing band gap gradient of the cascaded nanocrystal monolayers to enhance photosensitivity of the device platform. Substantial improvements are observed in the photosensitivity over a broadband spectral range (350-600 nm), with an approximately twofold enhancement factor along the entire operating wavelength range. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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