Plasmonic nanoparticle enhanced and extended performance of Light-sensitive nanocrystal skins
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Plasmonic nanoparticle enhanced and extended performance of Light-sensitive nanocrystal skins Shahab Akhavan1, Kivanc Gungor 1, and Hilmi Volkan Demir1,2 1
UNAM–Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, Department of Physics, Bilkent University, Ankara, 06800, Turkey 2 School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 639798, Singapore ABSTRACT We report on light-sensitive nanocrystal skin (LS-NS) platforms composed of monolayer visible nanocrystals (NCs) on top of bilayers of polyelectrolyte polymers. These LS-NS devices are operated on the principle of photogenerated potential buildup, unlike common photodetectors that operate on the basis of charge collection. The resulting devices are as highly sensitive as common photosensors, despite utilizing a monolayer of NCs and requiring no applied external bias. In this device architecture, using only a single NC monolayer also allows to reduce noise current generation. This LS-NS platform is highly stable under ambient conditions with fully sealed NC monolayer, promising for low-cost large-area UV/visible sensing applications. However, such visible NC based LS-NS devices exhibit limited performance in the long wavelength range due to the low optical absorption of these NCs (e.g., CdTe NCs) in this spectral range. Here, to enhance the device sensitivity, incorporating silver nanoparticles into LS-NS is proposed and demonstrated. For that, the optical absorption of CdTe monolayer NCs in the LS-NS devices is increased using the embedded silver nanostructures. With plasmon coupling, we observe a 2.6-fold enhancement factor in the photosensitivity around the localized surface plasmonic resonance peak of the nanostructures. Higher sensitivity improvement is also obtained at longer wavelengths. To predict the enhancement in the sensitivity of the LS-NS, numerical simulations are performed and the simulation results are found to agree well with the experimental data. Plasmonically enhanced LS-NS hold great promise for large-area photosensing applications extending from UV to IR including windows and facades of smart buildings. INTRODUCTION Colloidal semiconductor nanocrystals (NCs) are considered to make strong candidates as an alternative class of materials to replace conventional semiconductor epitaxial materials as well as rare-earth materials in various applications. NCs offer great potential for integrating them into optoelectronic devices because of their superior optical properties including bandgap tunability [1]. Since these materials have narrow emission and broad absorption bands, it is possible to control and fine-tune their emission spectrum while being able to optically excite them conveniently at short wavelengths, e.g., for color-conversion LEDs [2]. These materials are also considered as prospective materials to be used in photovoltaics and light sensing [3-4]. In addition to the aforementioned advantages of N
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