Photosensitive n-Type Doping Using Perovskite CsPbX3 Quantum Dots for Two-Dimensional MSe2 (M = Mo and W) Field-Effect Transistors

High-sensitivity hybrid MoSe2/AgInGaS quantum dot heterojunction photodetector

Zero-dimensional (0D)-two-dimensional (2D) hybrid photodetectors have received widespread attention due to their outstanding photoelectric performances. However, these devices with high performances mainly employ quantum dots that contain toxic elements as sensitizing layers, which restricts their practical applications. In this work, we used eco-friendly AgInGaS quantum dots (AIGS-QDs) as a highly light-absorbing layer and molybdenum diselenide (MoSe2) as a charge transfer layer to construct a 0D-2D hybrid photodetector. Notably, we observed that MoSe2 strongly quenches the photoluminescence (PL) of AIGS-QDs and decreases the decay time of PL in the MoSe2/AIGS-QDs heterojunction. The MoSe2/AIGS-QDs hybrid photodetector demonstrates a responsivity of 14.3 A W-1 and a high detectivity of 6.4 × 1011 Jones. Moreover, the detectivity of the hybrid phototransistor is significantly enhanced by more than three times compared with that of the MoSe2 photodetector. Our work suggests that 0D-2D hybrid photodetectors with multiplex I-III-VI QDs provide promising potential for future high-sensitivity photodetectors.

Optical Enhancement of Indirect Bandgap 2D Transition Metal Dichalcogenides for Multi-Functional Optoelectronic Sensors

The unique electrical and optical properties of transition metal dichalcogenides (TMDs) make them attractive nanomaterials for optoelectronic applications, especially optical sensors. However, the optical characteristics of these materials are dependent on the number of layers. Monolayer TMDs have a direct bandgap that provides higher photoresponsivity compared to multilayer TMDs with an indirect bandgap. Nevertheless, multilayer TMDs are more appropriate for various photodetection applications due to their high carrier density, broad spectral response from UV to near-infrared, and ease of large-scale synthesis. Therefore, this review focuses on the modification of the optical properties of devices based on indirect bandgap TMDs and their emerging applications. Several successful developments in optical devices are examined, including band structure engineering, device structure optimization, and heterostructures. Furthermore, it introduces cutting-edge techniques and future directions for optoelectronic devices based on multilayer TMDs.

Increased Mobility and Reduced Hysteresis of MoS2 Field-Effect Transistors via Direct Surface Precipitation of CsPbBr3-Nanoclusters for Charge Transfer Doping

Transition-metal dichalcogenides (TMDs) and metal halide perovskites (MHPs) have been investigated for various applications, owing to their unique physical properties and excellent optoelectronic functionalities. TMD monolayers synthesized via chemical vapor deposition (CVD), which are advantageous for large-area synthesis, exhibit low mobility and prominent hysteresis in the electrical signals of field-effect transistors (FETs) because of their native defects. In this study, we demonstrate an increase in electrical mobility by ∼170 times and reduced hysteresis in the current-bias curves of MoS2 FETs hybridized with CsPbBr3 for charge transfer doping, which is implemented via solution-based CsPbBr3-nanocluster precipitation on CVD-grown MoS2 monolayer FETs. Electrons injected from CsPbBr3 into MoS2 induce heavy n-doping and heal point defects in the MoS2 channel layer, thus significantly increasing mobility and reducing hysteresis in the hybrid FETs. Our results provide a foundation for improving the reliability and performance of TMD-based FETs by hybridizing them with solution-based perovskites.

Hybrid mixed-dimensional WTe2/CsPbI3perovskite heterojunction for high-performance photodetectors

Perovskites have showed significant potential for the application in photodetectors due to their outstanding electrical and optical properties. Integrating two-dimensional (2D) materials with perovskites can make full use of the high carrier mobility of 2D materials and strong light absorption of perovskite to realize excellent optoelectrical properties. Here, we demonstrate a photodetector based on the WTe₂/CsPbI₃heterostructure. The quenching and the shortened lifetime of photoluminescence (PL) for CsPbI₃perovskite confirms the efficient charge transfer at the WTe₂/CsPbI₃heterojunction. After coupled with WTe₂, the photoresponsivity of the CsPbI₃photodetector is improved by almost two orders of magnitude due to the high-gain photogating effect. The WTe₂/CsPbI₃heterojunction photodetector reveals a large responsivity of 1157 A W^-1and a high detectivity of 2.1 × 10¹³Jones. The results pave the way for the development of high-performance optoelectronic devices based on 2D materials/perovskite heterojunctions.

Inorganic Halide Perovskite Quantum Dots: A Versatile Nanomaterial Platform for Electronic Applications

Metal halide perovskites have generated significant attention in recent years because of their extraordinary physical properties and photovoltaic performance. Among these, inorganic perovskite quantum dots (QDs) stand out for their prominent merits, such as quantum confinement effects, high photoluminescence quantum yield, and defect-tolerant structures. Additionally, ligand engineering and an all-inorganic composition lead to a robust platform for ambient-stable QD devices. This review presents the state-of-the-art research progress on inorganic perovskite QDs, emphasizing their electronic applications. In detail, the physical properties of inorganic perovskite QDs will be introduced first, followed by a discussion of synthesis methods and growth control. Afterwards, the emerging applications of inorganic perovskite QDs in electronics, including transistors and memories, will be presented. Finally, this review will provide an outlook on potential strategies for advancing inorganic perovskite QD technologies.

Solution-Processed CsPbBr3 Quantum Dots/Organic Semiconductor Planar Heterojunctions for High-Performance Photodetectors

Planar heterojunctions (PHJs) are fundamental building blocks for construction of semiconductor devices. However, fabricating PHJs with solution-processable semiconductors such as organic semiconductors (OSCs) is a challenge. Herein, utilizing the orthogonal solubility and good wettability between CsPbBr₃ perovskite quantum dots (PQDs) and OSCs, fabrication of solution-processed PQD/OSC PHJs are reported. The phototransistors based on bilayer PQD/PDVT-10 PHJs show responsivity up to 1.64 × 10⁴ A W^-1 , specific detectivity of 3.17 × 10¹² Jones, and photosensitivity of 5.33 × 10⁶ when illuminated by 450 nm light. Such high photodetection performance is attributed to efficient charge dissociation and transport, as well as the photogating effect in the PHJs. Furthermore, the tri-layer PDVT-10/PQD/Y6 PHJs are used to construct photodiodes working in self-powered mode, which exhibit broad range photoresponse from ultraviolet to near-infrared, with responsivity approaching 10^-1 A W^-1 and detectivity over 10⁶ Jones. These results present a convenient and scalable production processes for solution-processed PHJs and show their great potential for optoelectronic applications.

Optoelectronic properties and interfacial interactions of two-dimensional Cs2PbX4-MSe2 (M = Mo, W) heterostructures

Constructing 2D inorganic perovskites and TMDs heterostructures is an effective method to design stable and high-performance perovskites optoelectronic applications. Here, we investigate the optoelectronic properties and interfacial interactions of Cs2PbX4-MSe2 (X = Cl, Br, I; M = Mo, W) heterostructures using first-principles calculations. Firstly, six Cs2PbX4-MSe2 interfaces remain stable in energy. With the halogen varying from Cl to I, the interlayer distances of Cs2PbX4-MSe2 heterostructures increase rapidly. The CBM and VBM of monolayer Cs2PbX4 are all higher than that of monolayer MSe2 and the charges transfer from Cs2PbX4 interfaces to MSe2 interfaces when they contact. Both Cs2PbX4-MSe2 heterostructures are type-II heterostructures, which can drive the photogenerated electrons and holes to move in opposite directions. What's more, Cs2PbCl4-MoSe2 heterostructures exhibit the highest charge transport efficiency among Cs2PbX4-MoSe2 heterostructures because Cs2PbCl4-MoSe2 heterostructures have the lowest exciton binding energies among Cs2PbX4-MSe2 heterostructures. In addition, the optical absorptions of all heterostructures are significantly higher than the corresponding Cs2PbX4 monolayers and MSe2 monolayers. The construction of Cs2PbX4-MoSe2 heterostructures is beneficial for improving the photoelectric performance of two-dimensional perovskite devices. Lastly, we found that the Cs2PbI4-WSe2 heterostructure has the largest PCE (18%) among Cs2PbX4-MSe2 heterostructures. The Cs2PbCl4-MoSe2 heterostructure exhibits great potential application in photodetector devices and the Cs2PbI4-WSe2 heterostructure has great potential application in solar cells.

Halide Perovskite Nanocrystal-Enabled Stabilization of Transition Metal Dichalcogenide Nanosheets

Transition metal dichalcogenide (TMD) nanosheets exfoliated in the liquid phase are of significant interest owing to their potential for scalable and flexible photoelectronic applications. Although various dispersants such as surfactants, oligomers, and polymers are used to obtain highly exfoliated TMD nanosheets, most of them are electrically insulating and need to be removed; otherwise, the photoelectric properties of the TMD nanosheets degrade. Here, inorganic halide perovskite nanocrystals (NCs) of CsPbX₃  (X = Cl, Br, or I) are presented as non-destructive dispersants capable of dispersing TMD nanosheets in the liquid phase and enhancing the photodetection properties of the nanosheets, thus eliminating the need to remove the dispersant. MoSe₂ nanosheets dispersed in the liquid phase are adsorbed with CsPbCl₃  NCs. The CsPbCl₃ nanocrystals on MoSe₂ efficiently withdraw electrons from the nanosheets, and suppress the dark current of the MoSe₂ nanosheets, leading to flexible near-infrared MoSe₂  photodetectors with a high ON/OFF photocurrent ratio and detectivity. Moreover, lanthanide ion-doped CsPbCl₃  NCs enhance the ON/OFF current ratio to >10⁶ . Meanwhile, the dispersion stability of the MoSe₂  nanosheets exfoliated with the perovskite NCs is sufficiently high.

Space-confined growth of large-mismatch CsPb(BrxCI1−x)3/GaN heterostructures with tunable band alignments and optical properties

Space-confined growth strategy is developed to grow large-mismatch CsPb(Br1−xClx)3/GaN heterostructures with type-II band alignment and tunable optical properties'.

Charge-Transfer Effect and Enhanced Photoresponsivity of WS2- and MoSe2-Based Field Effect Transistors with π-Conjugated Polyelectrolyte

The characteristics of field effect transistors (FETs) fabricated using two-dimensional (2D) transition-metal dichalcogenides (TMDCs) can be modulated by surface treatment of the active layers. In this study, an ionic π-conjugated polyelectrolyte, poly(9,9-bis(4'-sulfonatobutyl)fluorene-alt-1,4-phenylene) potassium (FPS-K), was used for the surface treatment of MoSe₂ and WS₂ FETs. The photoluminescence (PL) intensities of monolayer (1L)-MoSe₂ and 1L-WS₂ clearly decreased, and the PL peaks were red-shifted after FPS-K treatment, suggesting a charge-transfer effect. In addition, the n-channel current of both the MoSe₂ and WS₂ FETs increased and the threshold voltage (V_th) shifted negatively after FPS-K treatment owing to the charge-transfer effect. The photoresponsivity of the MoSe₂ FET under light irradiation (λ_ex = 455 nm) increased considerably, from 5300 A W^-1 to approximately 10 000 A W^-1, after FPS-K treatment, and similar behavior was observed in the WS₂ FET. The results can be explained in terms of the increase in electron concentration due to photogating. The external quantum efficiency and photodetectivity of both FETs were also enhanced by the charge-transfer effect resulting from surface treatment with FPS-K containing mobile cations (K⁺) and fixed anions (SO₃^-), as well as by the photogating effect. The variation in charge-carrier density due to the photogating and charge-transfer effects is estimated to be approximately 2 × 10¹² cm^-2. The results suggest that π-conjugated polyelectrolytes such as FPS-K can be a promising candidate for the passivation of TMDC-based FETs and obtaining enhanced photoresponsivity.

High-Performance Broadband Photodetector Based on Monolayer MoS2 Hybridized with Environment-Friendly CuInSe2 Quantum Dots

Monolayer MoS₂, a direct bandgap transition metal dichalcogenide (TMD), has attracted worldwide attention in electronics and optoelectronics. However, the performance of photodetectors based on monolayer MoS₂ is restricted to a weak optical absorption, narrow absorption range, and persistent photoconductance. Herein, benefiting from an easy solution process, high light absorption coefficient, and wide absorption range, environment-friendly CuInSe₂ quantum dots (QDs) are hybridized with monolayer MoS₂ for high-performance broadband photodetectors. Owing to the favorable type-II energy band alignment of MoS₂/CuInSe₂-QDs, the hybrid photodetector exhibits a broadband photoresponse from the ultraviolet to near-infrared region, with an ultrahigh photoresponsivity of 74.8 A/W at 1064 nm, and compared with those of the pristine MoS₂ device, the photoresponsivity and specific detectivity in the ultraviolet-visible region were enhanced by about 30 and 20 times, respectively. Furthermore, the formed depletion region at the MoS₂/CuInSe₂-QDs interface can significantly increase the photoresponse speed, and the accumulated holes in the QD side induce a strong photogating effect to improve the photoresponsive characteristics of the hybrid photodetector. Our work opens up opportunities for fabricating high-performance monolayer TMD-based broadband photodetectors.