Interfacial Charge Behavior Modulation in Perovskite Quantum Dot‐Monolayer MoS₂ 0D‐2D Mixed‐Dimensional van der Waals Heterostructures

Abstract

Fundamental understanding of charge behavior inside heterostructures is of vital importance for advancing high-performance optoelectronic applications. However, the charge behavior of 0D-2D mixed-dimensional van der Waals heterostructures (MvdWHs) in the photoexcited state remains elusive. In this work, an energy band alignment protocol is adopted to realize effective energy band structure engineering inside 0D-2D MvdWHs of perovskite quantum dots and MoS 2 monolayer with precisely designed typical type I and type II heterostructures, respectively. A profile and in-depth understanding of interfacial photoinduced charge behavior is determined from two opposite perspectives based on MvdWHs. Sufficient comparison of a series of optical characterization results, including Raman shift, quenched photoluminescence, visualized suppressed fluorescence intensity, and shortened fluorescence lifetime imaging, clearly verifies that interfacial charge behavior can be tailored by varying the band alignment in 0D-2D MvdWHs. Furthermore, the photoresponse performance and the relatively stronger and weaker photogating effects of such MvdWH-based phototransistors also demonstrate modulation of interfacial charge behavior in 0D-2D MvdWHs via energy band structure engineering, which is still feasible for optoelectronic performance optimization. These results are expected to shed light on designing novel functional devices and advancing the development process of 0D-2D MvdWHs in the foreseeable future.proposed stacked van der Waals heterostructures (vdWHs) have inspired worldwide efforts with rapid development of 2D materials. Such layer-by-layer assembled vdWHs could benefit from the high carrier mobilities, large surface-to-volume ratios, and especially flexible and semitransparent properties of atomically thin 2D materials. [4] However, the enhanced interlayer Coulombic interactions and Auger scattering processes in these 2D/2D vdWHs [5] as well as the inability to easily tune the energy band alignment for of the two given 2D layered materials has a great influence on the interfacial charge behavior, which is crucial to the performance of heterostructure-based functional devices. More recently, another type of vdWH was developed by integrating sizetunable semiconducting OD quantum dots (QDs) with 2D layered materials. This type of 0D-2D mixed-dimensional van der Waals heterostructure (MvdWH) has been demonstrated to possess various advantages, such as reduced Coulombic interactions, [6] easy preparation, and less constrained interfacial states. In addition, the interface in MvdWHs is more complex than that in conventional heterostructures, inducing interfacial disorder, synergistic effects, proximity effects, abrupt transitions of state density, and many other intriguing phenomena or properties. [4b,7] Hence, by combining the various remarkable optical properties of 0D-QDs with the unusual physical properties of 2D layered materials, 0D-2D MvdWHs may generate a fascinating interfacial charge behavior and exciting device performanc...

Ligand Engineering for Improved All‐Inorganic Perovskite Quantum Dot‐MoS2 Monolayer Mixed Dimensional van der Waals Phototransistor

“…In addition, the optical bandgaps of the perovskite QDs and monolayer MoS 2 can be determined by Tauc relation from the absorption spectra (Figure a and Figure S3 (Supporting Information)). The obtained direct bandgaps for monolayer MoS 2 and CsPbI 3− x Br x QDs are found to be 1.83 and 1.92 eV, respectively, consistent with previous reports . Thus, the energies of conduction band minimum ( E CBM ) of the perovskite QDs and monolayer MoS 2 are estimated at 3.75 and 4.45 eV.…”

“…Such MvdWH‐based devices have been demonstrated to be promising for ultrasensitive and broadband detection with high responsivity and photogain, because of outstanding intrinsic characteristics of perovskite QDs and 2D layered materials, respectively. Even though the interfacial electronic structure has been sufficiently engineered to manipulate the charge carrier behavior, the residue ligands introduced by the QDs and remained at the interface are still believed to be the dominated factor for possibility of further improvement . Consequently, the inevitable influence originated from the ligand is expected to be effectively mitigated for desired device performance.…”

“…To further demonstrate the significant influence of ligand engineering on the interfacial charge carrier behavior as well as related mixed dimensional van der Waals device performance, we take a phototransistor as a model device. Considering our previous works on the energy band engineering of mixed dimensional van der Waals heterostructures, we adopted monolayer MoS 2 (Figures S1 and S2, Supporting Information) with direct bandgap and high mobility to function as channel material. After subsequent modification of perovskite QD with or without ligand treatment, we realized the 0D–2D mixed dimensional van der Waals phototransistor as schematically illustrated in Figure a.…”

Light-Induced Interfacial Phenomena in Atomically Thin 2D van der Waals Material Hybrids and Heterojunctions

“…Another way to realize band gap engineering is to modify the band structure of the donor material. Wu et al 72 succeeded in changing the band alignment in perovskite−MoS 2 hybrids from a type I heterojunction to a type II heterojunction by changing the donor material from CH 3 NH 3 PbBr 3 QDs to CsPbI 3−x Br x QDs (Figure 6b). This band alignment modulation tailored the interfacial charge behavior, leading to a phototransistor performing better in type II hybrids with a gain of >10 5 , a photoresponsivity of 5.5 × 10 4 A/W, and a directivity of 1.95 × 10 12 Jones.…”

Strategies for Air‐Stable and Tunable Monolayer MoS2‐Based Hybrid Photodetectors with High Performance by Regulating the Fully Inorganic Trihalide Perovskite Nanocrystals

“…Perovskite materials with different dimensions have been integrated into optoelectronic devices to improve the performance . Among them, hybrid perovskite material/TMD photodetectors receive more attention due to their outstanding photoresponse performance . Up to now, the properties of HPs have been generally controlled by external working conditions, such as gate voltage, drain–source voltage, and power density of incident light .…”