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

Abstract

Colloidal PbS quantum dot (QD)/graphene hybrid photodetectors are emerging QD technologies for affordable infrared 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 freezeout 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 10 10 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.

Two-Dimensional Field-Effect Transistor Sensors: The Road toward Commercialization

“…2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (b) Adapted from ref . Copyright 2021 American Chemical Society.…”

Low-Temperature Induced Enhancement of Photoelectric Performance in Semiconducting Nanomaterials

“…By sacrificing the self-powered characteristic, photoconductors have superiorities in gain (G) [ 72 , 73 ] by applied bias voltage due to bias-enhanced carriers’ lifetime. In cryogenic enhancement tests, the photoconductive type is widely employed in two-dimensional materials [ 74 ] and quantum dots (QDs) [ 33 , 75 , 76 , 77 ]. The main problem faced by photoconductive devices is comparatively higher dark current.…”

“…On the basis of devices’ structures, numerous materials, simply classified in the right part of Figure 2 , varying from elemental to inorganic-organic hybrid semiconductors, have been researched for low-temperature photoelectric performance. As shown in Figure 2 a, the elemental materials are represented by graphene [ 33 , 81 , 82 , 83 ], black phosphorus [ 84 , 85 ], silicon [ 86 ], tellurium [ 47 ] and boron [ 87 ]. Since these 2D materials prefer the photoconductive mechanism, the utilization of the cooling method mainly influenced their photoconductive characteristics for devices’ performance.…”

“…Temperature variation first directly functions on materials, inducing fluctuations in energy level [ 27 , 28 , 29 ], carrier motions [ 30 ], density of traps/carriers [ 31 ] and crystal structure transition [ 32 ]. For cooling-enhanced materials, regulation in energy levels causes changes in absorption [ 28 ], barrier height [ 33 ] and so on [ 34 , 35 ], then influences photon absorption and charge transportation. Some intrinsic characteristics of carriers are reported to show huge enhancement from cooling, including mobility [ 36 ], diffusion length [ 37 ] and corresponding densities [ 38 ].…”

MoS2/WSe2vdW Heterostructures Decorated with PbS Quantum Dots for the Development of High-Performance Photovoltaic and Broadband Photodiodes

“…Quantum dots (QDs) are strong light absorbers that have been employed to enhance the gain of 2D-photoconductive photodetectors. − The mechanism underlying the enhanced gain is that photons are absorbed by the QDs under illumination to produce electron–hole pairs, anddue to the built-in electric fieldone carrier type is accumulated in the QDs, while the other is transferred into the channel . However, this scheme with an enhanced photoresponse has not yet been explored to improve the performance of 2D vdWH optical devices.…”