Flexible and fragmentable tandem photosensitive nanocrystal skins.
We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of single monolayers of colloidal water-soluble CdTe and CdHgTe nanocrystals (NCs) in adjacent junctions on a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation was significantly reduced while keeping the resulting PNS films considerably transparent. In each junction, photogenerated excitons are dissociated at the interface of the semi-transparent Al electrode and the NC layer, with holes migrating to the contact electrode and electrons trapped in the NCs. As a result, the tandem PNSs lead to an open-circuit photovoltage buildup equal to the sum of those of the two single junctions, exhibiting a total voltage buildup of 128.4 mV at an excitation intensity of 75.8 μW cm(-2) at 350 nm. Furthermore, we showed that these flexible PNSs could be bent over 3.5 mm radius of curvature and cut out in arbitrary shapes without damaging the operation of individual parts and without introducing any significant loss in the total sensitivity. These findings indicate that the NC skins are promising as building blocks to make low-cost, flexible, large-area UV/visible sensing platforms with highly efficient full-spectrum conversion.
UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, and Department of Physics, Bilkent University, Ankara, 06800, Turkey.
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Akhavan
UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, and Department of Physics, Bilkent University, Ankara, 06800, Turkey.
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Uran
UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, and Department of Physics, Bilkent University, Ankara, 06800, Turkey.
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Bozok
UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, and Department of Physics, Bilkent University, Ankara, 06800, Turkey.
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Gungor
UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, and Department of Physics, Bilkent University, Ankara, 06800, Turkey.
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Kelestemur
Physical Chemistry, Technische Universität Dresden, Dresden, 01062, Germany and Department of Nanochemistry, Istituto Italiano di Tecnologia, Genova, 16163, Italy.
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Lesnyak
Physical Chemistry, Technische Universität Dresden, Dresden, 01062, Germany.
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Gaponik
Physical Chemistry, Technische Universität Dresden, Dresden, 01062, Germany.
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Eychmüller
UNAM-Institute of Materials Science and Nanotechnology, Department of Electrical and Electronics Engineering, and Department of Physics, Bilkent University, Ankara, 06800, Turkey and School of Electrical and Electronic Engineering and School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 639798, Singapore. volkan@stanfordalumni.org.
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Demir