Charge Transport at CQDs/Graphene Interface for IR Light Detection
Gökhan Kara a, Matthias Grotevent a d, Dominik Bachmann a, Roman Furrer a, Maksym Kovalenko c d, Michel Calame a b, Ivan Shorubalko a
a Empa – Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Transport at Nanoscale Interfaces, Dübendorf, Switzerland, Switzerland
b University of Basel, Department of Physics and Swiss Nanoscience Institute , Basel, Switzerland, Switzerland
c Empa – Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Thin Films & Photovoltaics, Dübendorf, Switzerland
d ETH – Swiss Federal Institute of Technology Zürich, Department of Chemistry and Applied Biosciences, Laboratory of Inorganic Chemistry, Zürich, Switzerland
Online School
Proceedings of Online School on Fundamentals of Emerging Solar Cells (PVSCHOOL)
Online, Spain, 2021 February 10th - 12th
Organizers: Bruno Ehrler, Thomas Kirchartz and Elizabeth von Hauff
Poster, Gökhan Kara, 011
Publication date: 29th January 2021

The impact of nanocrystals on optoelectronic devices goes far beyond light-emitting diodes and solar cells. New concepts of photodetectors, also utilizing the photovoltaic effect, are exploiting the benefits of low-temperature solution-processing and size-tunable light absorption. Currently, the high price of state-of-the-art III-V semiconductors is limiting infrared (IR) detection to high-end applications in industry and research. Overcoming technological limitations in fabrication, phototransistors based on colloidal quantum dots (CQDs) and chemical vapor deposition (CVD) graphene promise a new generation of low-cost and sensitive IR detectors. Here, we explore the charge transport across the interface of a PbS QDs film and graphene with cryogenic experiments (300K to 80K). In addition to an increased photoresponse by one order of magnitude, we find a polarity change of the photosignal. Mediated by surface defects on the QDs, the interface energy barrier readjusts at low temperatures leading to this sign change.

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