Quantum Dot Photodetectors Research Articles

Analytical modelling for the dark current of TiO2/ZnS core shell quantum dot (CSQD) photodetectors

Dark current has a major contribution in the performance of a Quantum Dot (QD) photodetector. In this paper, a theoretical model is proposed to calculate the dark current of TiO2/ZnS CSQD photodetectors. In this model, the QD sub-band energy levels are calculated using three-dimensional symmetric quantum box considerations. The potential well is considered as finite. The observed theoretical results show the variation of electronic and hole sub-band transition variations with core size. It is also observed that, the dark current is very small, in order of 10−6 and lower for electronic transitions than the hole transitions for smaller, i.e. 8 nm core dimensions.

High performance hybrid MXene nanosheet/CsPbBr3 quantum dot photodetectors with an excellent stability

All-inorganic CsPbBr3 perovskite quantum dots (QDs) are considered as a new generation of photoelectric material for the implementations in photodetection owing to their remarkable optoelectronic properties and optimized stability. However, the combination of the abundant trap states and unfavorable carrier transportation poses a critical hurdle for the fabrication of high- performance photodetectors. In this study, a facile strategy to significantly enhance the performance of CsPbBr3 QD photodetectors via evenly blending 2D Ti3C2TX nanosheets is systematically demonstrated. The uniformly distributed Ti3C2TX nanosheets successfully confine incident fugacious photons throughout CsPbBr3 QD thin films as a result of the spontaneously intensified surface electromagnetic fields, and the transportation of photogenerated carriers from CsPbBr3 QDs are simultaneously accelerated due to the high conductivity and well-matched work function of the nanosheets. Meanwhile, the hot electrons excited from the nanosheets can also partially contribute to the increase in photocurrent, and thereby the performance of the device sensitively develops as a function of the concentration of the nanosheets. Correspondingly, a 300% enhancement is equally observed with external quantum efficiency and responsivity of the CsPbBr3 QD/MXene nanosheet photodetectors in comparison with the pristine one under 490 nm light illumination for a long period of 4 months in the atmospheric environment.

Vertically Stacked Full Color Quantum Dots Phototransistor Arrays for High-Resolution and Enhanced Color-Selective Imaging.

Color-selective multifunctional and multiplexed photodetectors have attracted considerable interest with the increasing demand for color filter-free optoelectronics which can simultaneously process multispectral signal via minimized system complexity. The low efficiency of color-filter technology and conventional laterally pixelated photodetector array structures often limit opportunities for widespread realization of high-density photodetectors. Here, low-temperature solution-processed vertically stacked full color quantum dot (QD) phototransistor arrays are developed on plastic substrates for high-resolution color-selective photosensor applications. Particularly, the three different-sized/color (RGB) QDs are vertically stacked and pixelated via direct photopatterning using a unique chelating chalcometallate ligand functioning both as solubilizing component and, after photoexposure, a semiconducting cement creating robust, insoluble, and charge-efficient QD layers localized in the a-IGZO transistor region, resulting in efficient wavelength-dependent photo-induced charge transfer. Thus, high-resolution vertically stacked full color QD photodetector arrays are successfully implemented with the density of 5500 devices cm-2 on ultrathin flexible polymeric substrates with highly photosensitive characteristics such as photoresponsivity (1.1 × 104 AW-1 ) and photodetectivity (1.1 × 1018 Jones) as well as wide dynamic ranges (>150dB).

Room-Temperature Direct Synthesis of PbSe Quantum Dot Inks for High-Detectivity Near-Infrared Photodetectors.

A PbSe colloidal quantum dot (QD) is typically a solution-processed semiconductor for near-infrared (NIR) optoelectronic applications. However, the wide application of PbSe QDs has been restricted due to their instability, which requires tedious synthesis and complicated treatments before being applied in devices. Here, we demonstrate efficient NIR photodetectors based on the room-temperature, direct synthesis of semiconducting PbSe QD inks. The in-situ passivation and the avoidance of ligand exchange endow PbSe QD photodetectors with high efficiency and low cost. By further constructing the PbSe QDs/ZnO heterostructure, the photodetectors exhibit the NIR responsivity up to 970 mA/W and a detectivity of 1.86 × 1011 Jones at 808 nm. The obtained performance is comparable to that of the state-of-the-art PbSe QD photodetectors using a complex ligand exchange strategy. Our work may pave a new way for fabricating efficient and low-cost colloidal QD photodetectors.

π–π Interactions Mediated Pyrene Based Ligand Enhanced Photoresponse in Hybrid Graphene/PbS Quantum Dots Photodetectors

AbstractHybrid graphene and quantum dots (QDs) photodetectors merge the excellent conductivity and ambipolar electric field sensitivity of graphene, with the unique properties of QDs. The photoresponsivity of these devices depends strongly on the charge transfer at the graphene/QDs interface. Here 1‐pyrene butyric acid (PBA)‐coated PbS QDs with single layer graphene (SLG) are used to investigate the effect of pyrene as a π–π mediator to enhance charge transfer at the SLG/QDs junction under illumination. The surface chemistry at the QD–QD and SLG/QD interface is studied with the conventional tetrabutylammonium iodide (TBAI) QD linker. The hybrid SLG/QD photodetectors with PBA as a SLG‐QD linker demonstrate a photoresponse up to 30% higher than that recorded for devices where only TBAI is used, due to the strong electron coupling between SLG and QDs. Transconductance measurements show that PBA provokes electron depletion in SLG ascribed to the tendency to delocalize the QDs holes, favoring their transfer to SLG. This surface ligand is found to improve the interaction between the QDs light absorbers and the SLG charge collector, leading to an increased photodetection response. This demonstrates that ligand engineering can enhance charge dynamics and boost the performance of the hybrid device.

Near-Infrared Photoresponse in Ge/Si Quantum Dots Enhanced by Photon-Trapping Hole Arrays.

Group-IV photonic devices that contain Si and Ge are very attractive due to their compatibility with integrated silicon photonics platforms. Despite the recent progress in fabrication of Ge/Si quantum dot (QD) photodetectors, their low quantum efficiency still remains a major challenge and different approaches to improve the QD photoresponse are under investigation. In this paper, we report on the fabrication and optical characterization of Ge/Si QD pin photodiodes integrated with photon-trapping microstructures for near-infrared photodetection. The photon traps represent vertical holes having 2D periodicity with a feature size of about 1 μm on the diode surface, which significantly increase the normal incidence light absorption of Ge/Si QDs due to generation of lateral optical modes in the wide telecommunication wavelength range. For a hole array periodicity of 1700 nm and hole diameter of 1130 nm, the responsivity of the photon-trapping device is found to be enhanced by about 25 times at μm and by 34 times at μm relative to a bare detector without holes. These results make the micro/nanohole Ge/Si QD photodiodes promising to cover the operation wavelength range from the telecom O-band (1260–1360 nm) up to the L-band (1565–1625 nm).

Effect of Adhesive Layers on Photocurrent Enhancement in Near-Infrared Quantum-Dot Photodetectors Coupled with Metal-Nanodisk Arrays

Effect of Adhesive Layers on Photocurrent Enhancement in Near-Infrared Quantum-Dot Photodetectors Coupled with Metal-Nanodisk Arrays

Ambient stability improvement of CQD photodetectors by low-temperature deposited graphene encapsulation

In this work, we have investigated the ambient stability improvement of colloidal quantum dots (CQD) photodetectors by graphene encapsulation. The low temperature deposited graphene is performed to act as an isolating membrane between PbS CQDs and the ambient environment. The oxidization of PbS CQDs can be significantly inhibited with a graphene isolating membrane. In addition, the optoelectronic characteristics of PbS CQDs-based photodetectors encapsulated by graphene are well maintained even exposed in ambient for a month. This work paves the way for the fabrication and application of the air-stable CQDs.

Modeling and Low Light Level Detection Based on Quantum Dots Photodetector

In this paper, an equivalent circuit modeling method of photodetector is proposed, and the equivalent circuit model of quantum dots photodetector is established. Experimental results show that the simulation curves and parameters agree very well with the measured results. The 10 picowatts power focused laser is readout based on readout circuits and low light level detection system at 77 K temperature. The 7 mV response voltage is achievable under 29 μs integration time and −3.1 V bias voltage. The voltage responsivity has reached 7 × 108 V/W.

Facet-Oriented Coupling Enables Fast and Sensitive Colloidal Quantum Dot Photodetectors.

Charge carrier transport in colloidal quantum dot (CQD) solids is strongly influenced by coupling among CQDs. The shape of as-synthesized CQDs results in random orientational relationships among facets in CQD solids, and this limits the CQD coupling strength and the resultant performance of optoelectronic devices. Here, colloidal-phase reconstruction of CQD surfaces, which improves facet alignment in CQD solids, is reported. This strategy enables control over CQD faceting and allows demonstration of enhanced coupling in CQD solids. The approach utilizes post-synthetic resurfacing and unites surface passivation and colloidal stability with a propensity for dots to couple via (100):(100) facets, enabling increased hole mobility. Experimentally, the CQD solids exhibit a 10× increase in measured hole mobility compared to control CQD solids, and enable photodiodes (PDs) exhibiting 70% external quantum efficiency (vs 45% for control devices) and specific detectivity, D*>1012 Jones, each at 1550nm. The photodetectors feature a 7ns response time for a 0.01mm2 area-the fastest reported for solution-processed short-wavelength infrared PDs.

Effect of surface oxygen vacancy defects on the performance of ZnO quantum dots ultraviolet photodetector* *Project supported by the National Natural Science Foundation of China (Grant Nos. 62074148, 61875194, 11727902, 12074372, 11774341, 11974344, 61975204, and 11804335), the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No. 2020225), the Open Project of the State Key Laboratory of Luminescence

The slower response speed is the main problem in the application of ZnO quantum dots (QDs) photodetector, which has been commonly attributed to the presence of excess oxygen vacancy defects and oxygen adsorption/desorption processes. However, the detailed mechanism is still not very clear. Herein, the properties of ZnO QDs and their photodetectors with different amounts of oxygen vacancy (VO) defects controlled by hydrogen peroxide (H2O2) solution treatment have been investigated. After H2O2 solution treatment, VO concentration of ZnO QDs decreased. The H2O2 solution-treated device has a higher photocurrent and a lower dark current. Meanwhile, with the increase in VO concentration of ZnO QDs, the response speed of the device has been improved due to the increase of oxygen adsorption/desorption rate. More interestingly, the response speed of the device became less sensitive to temperature and oxygen concentration with the increase of VO defects. The findings in this work clarify that the surface VO defects of ZnO QDs could enhance the photoresponse speed, which is helpful for sensor designing.

Minimization of bandstructure dependent dark current in InAs/GaAs quantum dot photodetectors

The paper presents a theoretical model which illustrates the electron capture and emission dynamics in InAs/GaAs quantum dot (QD) photodetector and describes the bandstructure dependent dark current generation. Result of the study predicts the possibility of excessive dark current that depends on the different rates of thermal and phonon assisted tunneling emissions from the quantized energy states. Variation of QD size can alter the quantized states and control the emission rates. Our findings shows that high dark current generated in a QD at a particular temperature and bias voltage can be reduced significantly by changing the size. Hence, optimum QD size is proposed that generates minimum the dark current at different temperatures of operation and applied bias. • Proposes a theoretical model on dark current generation in InAs/GaAs quantum dot photodetectors. • Illustrates modification of quantum dot size for altering the bandstructure. • Illustrates bandstructure dependent dark current generation mechanism at different voltages and operating temperatures. • Proposes optimizing the quantum dot size for minimizing dark current at different voltages and operating temperatures. • This work is a guideline for minimizing dark current and improve the performance of quantum dot photodetectors.

66‐1: High Resolution Quantum Dot Global Shutter Imagers

Quantum dot photodetectors are a promising platform technology that ST Microelectronics has developed, scaled‐up, and is ready to commercialize. Our quantum dot‐based global shutter imagers are responsive from UV to SWIR wavelengths at high resolution, high efficiency, and low dark currents, with good reliability and very competitive cost. Sampling to customers is now ready to start.

Enhanced performance of UV photodetector of MoS2 quantum dots-decorated ZnO nanorods

Two-dimensional transition metal dichalcogenides such as molybdenum disulfide (MoS2) have attracted great attention due to their unique optical, electrical and chemical properties. MoS2 quantum dots (QDs) exhibit strong quantum confinement, high surface area and notable active edge sites compared to their bulk. In this work, MoS2 QDs were attached on the surface of ZnO nanorods (NRs) grown on interdigitated ITO substrates and then used as photodetector. MoS2 QDs were synthesized by a new ultrafast way pulsed laser ablation (PLA) in liquid method and then spincoated on the surface of ZnO NRs. The pristine ZnO and ZnO/MoS2 QDs photodetector were investigated under UV and visible light (325 nm, 505 nm and 635 nm) with the bias voltage -5 V to 5 V. The results show that the decoration of ZnO NRs by MoS2 QDs could enhance the sensitivity, responsivity and detectivity under UV irradiation. This may due to the decrease of dark current as the result of passivation of surface defects of ZnO NRs by MoS2 QDs.

The Display Week 2021 Symposium Preview

The Display Week 2021 Symposium Preview

TlGaN Quantum-Dot Photodetectors

Due to the lack of work in structures containing thallium (Tl), this work is devoted to study of Ga8Tl2N quantum-dot photodetectors. Parameters are specified first. This structure is shown to have low absorption. Enough quantum efficiency is obtained. This detector works at 360–460 nm and peaked at 410 nm, which can be used in optical coherence tomography applications.

Plasmonic-coupled quantum dot photodetectors for mid-infrared photonics.

A plasmonic-coupled, InAs-based quantum dot photodetector fabricated for mid-wave infrared photonics is reported. The detector is designed to provide a broadband absorption [full width at half maximum (FWHM) ≳ 2 µm] peaked at ∼5.5 µm, corresponding to transitions from the ground state of the quantum dot to the quasi-continuum resonance state above the quantum well. From the coupling of this transition to the surface plasma wave (SPW) excited by an Au film atop the detector, fabricated with a 1.5 µm-period, 2-dimensional array of square holes, a narrowband SPW enhancement peaked at 4.8 µm with an FWHM less than 0.5 µm is achieved. At ∼90 K, a peak responsivity enhanced ∼5× by the plasmonic coupling is observed. Simulation reveals that this enhancement corresponds to collecting ∼6% of the incident light; ∼40% of the total absorption by the SPW excitation at the peak wavelength.

CsPbBr3 quantum dots photodetectors boosting carrier transport via molecular engineering strategy

CsPbBr3 quantum dots photodetectors boosting carrier transport via molecular engineering strategy

Speed enhancement of ultraviolet photodetector base on ZnO quantum dots by oxygen adsorption on surface defects

Applications of ZnO quantum dots (QDs) in photodetectors are generally limited by a slower response speed and a higher dark current. The corresponding mechanism is not very clear, and how to resolve these problems is still in big challenge. Herein, we have demonstrated a photodetector on 700 nm-thick ZnO QDs film with a large number of oxygen vacancy defects by adjusting the ratio of the reactants and the reaction time. The device exhibits a quick response speed with a rise time of ~1.00 s and a recovery time of ~0.19 s. Meanwhile, the dark current and the responsivity under 730 μW/cm2 UV light illumination were found to be 20 pA and 260 mA/W under 10 V bias, respectively. The mechanism of these phenomena has been investigated, and the fast response speed of ZnO QDs photodetector in the air should originate from the adsorption/desorption of oxygen on the surface oxygen vacancy defects of ZnO QDs. The findings in this work can be used to guide design of high-performance photodetectors based on ZnO QDs and other nanomaterials with large surface to volume ratio.

Enhanced detectivity of PbS quantum dots infrared photodetector by introducing the tunneling effect of PMMA

With extremely high optical absorption coefficient in infrared regime, lead sulfide (PbS) quantum dots (QDs)-based photodetectors are promising for diverse applications. In recent years, synthesis of materials has made great progress, but the problem of low sensitivity of quantum dots photodetector still unresolved. In this work, the introduction of a tunneling organic layer effectively address this problem. The dark current is decreased by the appropriate thickness of polymethyl methacrylate (PMMA) barrier layer by suppressing the spontaneous migration of ions, and the photogenerated carriers are little effected, thereby the responsivity of the device is improved. As a result, the device exhibits a high responsivity of 3.73 × 105 mA W−1 and a giant specific detectivity of 4.01 × 1013 Jones at a low voltage of −1 V under 1064 nm illumination. In the self-powered mode, the responsivity reaches a value of 157.6 mA W−1, and the detectivity up to 5.9 × 1011 Jones. The performance of the photodetectors is obviously better than most of the reported QDs photodetectors. The design of this device structure provides a new solution to the problem of low sensitivity and high leakage current of quantum dots based infrared photodetectors.