Interface Engineering in Hybrid Quantum Dot–2D Phototransistors

Abstract

The hybridization of two-dimensional transition metal dichalcogenides (TMDCs) withcolloidal quantum dots has been demonstrated to be an ideal platform for low darkcurrent and highly sensitive photodetection due to a carrier recirculation mechanism producing very high gain. However, TMDCs react sensitively to surface modifications and the sensitizing quantum dots introduce uncontrolled doping, which prevent these hybrids from reaching large on/off ratios, met in pristine 2D transistors. In this work,

Solution-processed semiconductors for next-generation photodetectors

“…The reduction of interface trap states is important to achieve high sub-threshold swings (the amount of voltage required to produce a one decade change in dark current) that increase the SNR. 90 The growing space in the 2D materials library, as well as the increasing understanding after intense research in the optoelectronic properties photosensitizing layer, picture a promising future for this device architecture.…”

Organic Field‐Effect Transistor for Energy‐Related Applications: Low‐Power‐Consumption Devices, Near‐Infrared Phototransistors, and Organic Thermoelectric Devices

“…The material form options for light sensitizers can either be single crystals, thin films, heterojunctions, or even discrete quantum dots. [173,174] Due to the quantum confinement effect, the bandgap of CQDs can be continuously tuned by varying the QDs size, allowing MIR absorption ability with a wavelength longer than 3 µm for HgTe QDs, providing great potential for IR sensing of this kind of material despite the material's toxicity. Meanwhile, the selection of the bottom semiconductor can focus on large bandgap organic small molecules with high mobility and a large on/off ratio to enhance both the photoresponsivity and sensing dynamic range, or 2D-like organic single crystals to obtain an extremely low dark current.…”

MoS2–HgTe Quantum Dot Hybrid Photodetectors beyond 2 µm

“…[29][30][31] The use of semiconducting 2D channels is of particular promise for they enable the operation of the transistor in the depletion mode, offering thus the advantage of low 3 leakage current in dark conditions with appropriate interface engineering. [32] This feature is of paramount importance especially in low-bandgap IR photodetectors that suffer from large dark currents and therefore large noise currents at room temperature.…”

“…After the ALD deposition of TiO2, the MoS2 field effect transistors (FETs) performance was maintained but with decreased threshold voltage, suggesting an n-type doping effect for the MoS2 due to the removal of adsorbates or oxygen vacancies in nonstoichiometric TiO2 film. [32] TiO2 is widely studied ntype semiconductor with large band gap of 3.2 eV and low mobility which can act as transparent window for vis/IR light and has negligible current leakage through this layer. [34] Upon deposition of HgTe QDs on the TiO2 encapsulated MoS2 channel, the hybrids device preserves well gate modulated current with low off-current (~pA) and high on-current (~10 µA) closed to that in the pristine MoS2.…”

“…[30] However, the presence of the TiO2 buffer layer suppresses this interaction and preserves the FETs performance characteristic of MoS2. [32] From ultraviolet photoelectron spectroscopy (UPS) measurement ( Figure S3), the energy band of HgTe QDs has been determined, which forms a type-II band alignment with TiO2/MoS2 as shown in Figure 2a. Upon light illumination on the HgTe QDs, the photo-generated electrons are transferred into the MoS2 channel through the thin TiO2 layer due to the built-in field while the holes remain trapped in the QDs layer with a timescale of .…”