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Temperature-Dependent Charge Carrier Transfer in Colloidal Quantum Dot/Graphene Infrared Photodetectors

preprint
submitted on 13.08.2020 and posted on 13.08.2020 by Matthias Grotevent, Claudio U. Hail, Sergii Yakunin, Dominik Bachmann, Gökhan Kara, Dmity N. Dirin, Michel Calame, Dimos Poulikakos, Maksym V. Kovalenko, Ivan Shorubalko
Colloidal PbS quantum dot (QD)/graphene hybrid photodetectors are emerging QD technologies for affordable infra-red light detectors. By interfacing the QDs with graphene, the photosignal of these detectors is amplified, leading to high responsivity values. While these detectors have been mainly operated at room temperature, low-temperature operation is required for extending their spectral sensitivity beyond a wavelength of 3 μm. Here, we unveil the temperature-dependent response of PbS QD/graphene photodetectors by performing steady-state and time-dependent measurements over a large temperature range of 80–300 K. We find that the temperature dependence of photo-induced charge carrier transfer from the QD layer to graphene is (i) not impeded by freeze-out of the (Schottky-like) potential barrier at low temperatures, (ii) tremendously sensitive to QD surface states (surface oxidation), and (iii) minimally affected by the ligand exposure time and QD layer thickness. Moreover, the specific detectivity of our detectors increases with cooling, with a maximum measured specific detectivity of at least 1010 Jones at a wavelength of 1280 nm and temperature of 80 K, which is an order of magnitude larger compared to the corresponding room temperature value. The temperature- and gate-voltage-dependent characterization presented here constitute an important step in expanding our knowledge of charge transfer at interfaces of low dimensional materials and towards the realization of next-generation optoelectronic devices.

Funding

Swiss Space Office Project "MAGDA"

Swiss National Science Foundation Project No. 200021_182790

History

Email Address of Submitting Author

matthias.grotevent@empa.ch

Institution

Empa

Country

Switzerland

ORCID For Submitting Author

0000-0003-0821-2959

Declaration of Conflict of Interest

The authors declare no competing financial interest.

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