Photoconductivity of PbS Quantum Dot Films in Plasmonic Nanogaps
Dario Grimaldi a, Emil Kelderer a, Andreas Hohenau a, Harald Ditlbacher a, Dmitry N. Dirin b, Maksym V. Kovalenko b, Joachim R. Krenn a
a Institute of Physics, University of Graz, Austria, Austria
b ETH Zurich, Laboratory of Inorganic Chemistry, Department of Chemistry & Applied Biosciences, Vladimir-Prelog-Weg, 1, Zürich, Switzerland
Proceedings of Internet Conference for Quantum Dots (iCQD)
Online, Spain, 2020 July 14th - 17th
Organizers: Quinten Akkerman, Raffaella Buonsanti, Zeger Hens and Maksym Kovalenko
Oral, Dario Grimaldi, presentation 039
Publication date: 3rd July 2020

Colloidal quantum dots are attractive building blocks for highly miniaturized and integrated components in optoelectronic applications. In combination with rather simple processability at room temperature, this has led to considerable interest in quantum dot photodetectors in recent years [1]. In particular, PbS quantum dot film photodetectors have been realized with record performance in the visible and near infrared spectral range [2]. Here, we investigate highly miniaturized PbS photodetectors involving only a few to a few hundred quantum dots, aiming at efficient light-to-current conversion with a nanoscale footprint.

We investigate PbS-MAPbI3 quantum dots in lithographically tailored gold electrodes as a controlled platform for characterizing the photocurrents from small quantum dot ensembles. The electrode gaps filled with quantum dots are varied between 15 nm and 1.5 µm, the generated currents are in the pA-nA range for nW-µW light power. The MAPbI3 ligands enable carrier tunneling between the individual quantum dots when deposited as closely packed ensembles by spin coating.

We demonstrate that PbS-MAPbI3 quantum dots are reliable nanoscale light/current converters and correlate the measured photocurrents to the quantum dot number, the gap voltage and light irradiance. For the latter, we find a photocurrent power law dependence with an exponent of 2/3. Furthermore, we probe the role of plasmonic effects in the gold electrodes and image by scanning photocurrent microscopy the spatial dependence of photocurrent generation.

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