Omnidirectional Harvesting of Weak Light Using a Graphene Quantum Dot-Modified Organic/Silicon Hybrid Device

Highly DUV to NIR-II responsive broadband quantum dots heterojunction photodetectors by integrating quantum cutting luminescent concentrators

Low-cost, high-performance, and uncooled broadband photodetectors (PDs) have potential applications in optical communication etc., but it still remains a huge challenge to realize deep UV (DUV) to the second near-infrared (NIR-II) detection for a single broadband PD. Herein, a single PD affording broadband spectral response from 200 to 1700 nm is achieved with a vertical configuration based on quantum dots (QDs) heterojunction and quantum cutting luminescent concentrators (QC-LC). A broadband quantum dots heterojunction as absorption layer was designed by integrating CsPbI3:Ho3+ perovskite quantum dots (PQDs) and PbS QDs to realize the spectral response from 400 to 1700 nm. The QC-LC by employing CsPbCl3:Cr3+, Ce3+, Yb3+, Er3+ PQDs as luminescent conversion layer to collect and concentrate photon energy for boosting the DUV-UV (200-400 nm) photons response of PDs by waveguide effect. Such broadband PD displays good stability, and outstanding sensitivity with the detectivity of 3.19 × 1012 Jones at 260 nm, 1.05 × 1013 Jones at 460 nm and 2.23 × 1012 Jones at 1550 nm, respectively. The findings provide a new strategy to construct broadband detector, offering more opportunities in future optoelectronic devices.

High-Performance and Stable Sb2S3 Thin-Film Photodetectors for Potential Application in Visible Light Communication

Photodetectors (PDs) are critical parts of visible light communication (VLC) systems for achieving efficient photoelectronic conversion and high-fidelity transmission of signals. Antimony sulfide (Sb₂S₃) as a nontoxic, high optical absorption coefficient, and low-cost semiconductor becomes a promising candidate for applications in VLC systems. Particularly, Sb₂S₃ PDs were verified to have significantly weak light detection ability in the visible region. However, the response speed of Sb₂S₃ PDs with existing device structures is still relatively slow. Herein, through optimizing the device structure for the p-i-n type PDs, a p-type Sb₂Se₃ hole transport layer (HTL) is designed to enhance the built-in electric field and to accelerate the migration of photogenerated carriers for the high responsivity and fast response speed. The optimal thickness of the structure is obtained through the simulation of SCAPS-1D software, and the optimized devices show high-performance parameters, including a responsivity of 0.34 A W^-1, a specific detectivity (D^*) of 2.20 × 10¹² Jones, the -3 dB bandwidth of 440 kHz, high stability, and the value of the Sb₂S₃ PDs can reach 60% in the range of 360-600 nm, which indicates that the device is very suitable for working in the visible light band. In addition, the resulting Sb₂S₃ PD is successfully integrated into VLC systems by designing a matched light detection circuit. The results suggest that the Sb₂S₃ PDs are expected to provide an alternative to future VLC system applications.

Bioresource-Functionalized Quantum Dots for Energy Generation and Storage: Recent Advances and Feature Perspective

The exponential increase in global energy demand in daily life prompts us to search for a bioresource for energy production and storage. Therefore, in developing countries with large populations, there is a need for alternative energy resources to compensate for the energy deficit in an environmentally friendly way and to be independent in their energy demands. The objective of this review article is to compile and evaluate the progress in the development of quantum dots (QDs) for energy generation and storage. Therefore, this article discusses the energy scenario by presenting the basic concepts and advances of various solar cells, providing an overview of energy storage systems (supercapacitors and batteries), and highlighting the research progress to date and future opportunities. This exploratory study will examine the systematic and sequential advances in all three generations of solar cells, namely perovskite solar cells, dye-sensitized solar cells, Si cells, and thin-film solar cells. The discussion will focus on the development of novel QDs that are economical, efficient, and stable. In addition, the current status of high-performance devices for each technology will be discussed in detail. Finally, the prospects, opportunities for improvement, and future trends in the development of cost-effective and efficient QDs for solar cells and storage from biological resources will be highlighted.

Bioinspired Compound Eyes for Diffused Light-Harvesting Application

Natural compound eyes endow arthropods with wide-field high-performance light-harvesting capability that enables them to capture prey and avoid natural enemies in dim light. Inspired by natural compound eyes, a curved artificial-compound-eye (cACE) photodetector for diffused light harvesting is proposed and fabricated, and its light-harvesting capability is systematically investigated. The cACE photodetector is fabricated by introducing a cACE as a light-harvesting layer on the surface of a silicon-based photodetector, with the cACE being prepared via planar artificial-compound-eye (pACE) template deformation. The distinctive geometric morphology of the as-prepared cACE effectively reduces its surface reflection and the dependence of the projected area on the incident light direction, thereby significantly improving the light-harvesting ability and output photocurrent of the silicon-based photodetector. Furthermore, the performances of cACE, pACE, and bare polydimethylsiloxane (PDMS)-attached photodetectors as diffused light detectors are investigated under different luminances. The cACE-photodetector output photocurrent is 1.395 and 1.29 times those of the bare PDMS-attached and pACE photodetectors, respectively. Moreover, this photodetector has a desirable geometric shape. Thus, the proposed cACE photodetector will facilitate development of high-performance photodetectors for luminance sensing.

Photoelectronic Properties of End-bonded InAsSb Nanowire Array Detector under Weak Light

A simple fabrication of end-bonded contacts InAsSb NW (nanowire) array detector to weak light is demonstrated in this study. The detector is fabricated using InAsSb NW array grown by molecular beam epitaxy on GaAs substrate. The metal-induced gap states are induced by the end-bonded contact which suppresses the dark current at various temperatures. The existence of the interface dipole due to the interfacial gap states enhances the light excitation around the local field and thus upgrades the photoresponsivity and photodetectivity to the weak light. The light intensity of the infrared light source in this report is 14 nW/cm² which is about 3 to 4 orders of magnitude less than the laser source. The responsivity of the detector has reached 28.57 A/W at room temperature with the light (945 nm) radiation, while the detectivity is 4.81 × 10¹¹ cm·Hz^1/2 W^-1. Anomalous temperature-dependent performance emerges at the variable temperature experiments, and we discussed the detailed mechanism behind the nonlinear relationship between the photoresponse of the device and temperatures. Besides, the optoelectronic characteristics of the detector clarified that the light-trapping effect and photogating effect of the NWs can enhance the photoresponse to the weak light across ultraviolet to near-infrared. These results highlight the feasibility of the InAsSb NW array detector to the infrared weak light without a cooling system.

Light-Driven Piezo- and Triboelectricity in Organic-Inorganic Metal Trihalide Perovskite toward Mechanical Energy Harvesting and Self-powered Sensor Application

A single-structured multifunctional device capable of energy harvesting and sensing multiple physical signals has significant potential for a wide range of applications in the Internet of Things (IoT). In this study, the fabricated single-structured device based on methylammonium lead iodide-polyvinylidene fluoride (MAPbI₃-PVDF) composite can harvest mechanical energy and simultaneously operate as a self-powered light and pressure sensor because of the combined photoelectric and piezoelectric/triboelectric properties of the MAPbI₃-PVDF composite. Light-dependent dielectric and piezoelectric properties of composite films are thoroughly investigated. Light and contact electrification effect on device performance in both piezoelectric and triboelectric modes is also systematically investigated. When the device is operated as a harvester in both piezoelectric and triboelectric modes, remarkable light-driven outputs were observed under illumination; the outputs decreased in the piezoelectric mode, while they increased in the triboelectric mode. Such light-controlled properties enabled the device to operate as a self-powered photodetector with outstanding responsivity (∼129.2 V/mW), rapid response time (∼50 ms), and satisfactory detectivity (∼1.4 × 10¹⁰ Jones) in the piezoelectric mode. The same device could also operate as a pressure sensor that exhibited excellent pressure sensitivity values of 0.107 and 0.194 V/kPa in the piezoelectric and triboelectric modes, respectively. In addition, the device exhibits a fast response time with long-term on-off switching properties, excellent mechanical durability, and long-term stability.

Click chemical assembly and validation of bio-functionalized superparamagnetic hybrid microspheres

Surface derivatized magnetic nanoparticles have been commonly used for magnetic separation. Facile mechanisms are needed to be developed for the design of bio-functionalized magnetic hybrid materials, where the surfaces can be re-generated for the re-use of the developed platforms. Superparamagnetic iron oxide nanoparticles with a diameter below 10 nm were synthesized via a novel microwave-assisted hydrothermal method in the presence of citrate ions, which allowed to obtain uniform and negatively charged nanoparticles. These were then coupled with Poly-l-lysine (PLL), forming micrometer-sized self-assembled spherical entities. Cross-linking the PLL within these microspheres with glutaraldehyde stabilized them chemically and mechanically. The active bio-functionality was introduced by a protein grafting methodology, using m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester (SMBS). The Moringa oleifera Coagulant Protein (MOCP) from a seed extract was employed for its characteristic coagulation activity. The performance of the MOCP functionalized microspheres was evaluated as a function of turbidity removal of problematic colloidal clay from water via magnetic separation, resulting in over 80% of activity within 15 min. Surface of these hybrid materials can be re-generated by treatment with alcohol, allowing their easy magnetic separation and re-use. The rapid and strong response with tunable magnetic property makes these hybrid microspheres a powerful tool for many potential applications, due to the general applicability of the developed methodology.

Variation of Optical Properties of Nitrogen-doped Graphene Quantum Dots with Short/Mid/Long-wave Ultraviolet for the Development of the UV Photodetector

Nitrogen-doped graphene quantum dots (NGQDs) synthesized from a single glucosamine precursor are utilized to develop a novel UV photodetector. Optical properties of NGQDs can be altered with short- (254 nm), mid- (302 nm), and long-wave (365 nm) ultraviolet (UV) exposure leading to the reduction of absorption from deep to mid UV (200-320 nm) and enhancement above 320 nm. Significant quenching of blue and near-IR fluorescence accompanied by the dramatic increase of green/yellow emission of UV-treated NGQDs can be used as a potential UV-sensing mechanism. These emission changes are attributed to the reduction of functional groups detected by Fourier transformed infrared spectroscopy and free-radical-driven polymerization of the NGQDs increasing their average size from 4.70 to 11.20 nm at 60 min treatment. Due to strong UV absorption and sensitivity to UV irradiation, NGQDs developed in this work are utilized to fabricate UV photodetectors. Tested under long-/mid-/short-wave UV, these devices show high photoresponsivity (up to 0.59 A/W) and excellent photodetectivity (up to 1.03 × 10¹¹ Jones) with highly characteristic wavelength-dependent reproducible response. This study suggests that the optical/structural properties of NGQDs can be controllably altered via different wavelength UV treatment leading us to fabricate NGQD-based novel UV photodetectors providing high responsivity and detectivity.

Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications

Graphene quantum dots (GQDs) that are flat 0D nanomaterials have attracted increasing interest because of their exceptional chemicophysical properties and novel applications in energy conversion and storage, electro/photo/chemical catalysis, flexible devices, sensing, display, imaging, and theranostics. The significant advances in the recent years are summarized with comparative and balanced discussion. The differences between GQDs and other nanomaterials, including their nanocarbon cousins, are emphasized, and the unique advantages of GQDs for specific applications are highlighted. The current challenges and outlook of this growing field are also discussed.

Memory phototransistors based on exponential-association photoelectric conversion law

Ultraweak light detectors have wide-ranging important applications such as astronomical observation, remote sensing, laser ranging, and night vision. Current commercial ultraweak light detectors are commonly based on a photomultiplier tube or an avalanche photodiode, and they are incompatible with microelectronic devices for digital imaging applications, because of their high operating voltage and bulky size. Herein, we develop a memory phototransistor for ultraweak light detection, by exploiting the charge-storage accumulative effect in CdS nanoribbon. The memory phototransistors break the power law of traditional photodetectors and follow a time-dependent exponential-association photoelectric conversion law. Significantly, the memory phototransistors exhibit ultrahigh responsivity of 3.8 × 10⁹ A W⁻¹ and detectivity of 7.7 × 10²² Jones. As a result, the memory phototransistors are able to detect ultraweak light of 6 nW cm⁻² with an extremely high sensitivity of 4 × 10⁷. The proposed memory phototransistors offer a design concept for ultraweak light sensing devices.

CdS nanostructures can enable memory based photodetection by charge-storage accumulative effect. Here, the authors report CdS nanoribbons-based memory phototransistors with high responsivity of 3.8 × 10⁹ A/W and detectivity of 7.7 × 10²² Jones that can detect weak light of 6 nW/cm².

Structural Engineering of Si/TiO2/P3HT Heterojunction Photodetectors for a Tunable Response Range

To meet the demands of next-generation optoelectronic circuits, the design and construction of photodetectors with a tunable photoresponse range and self-powered feature are urgently required. To achieve selective wavelength detection, a band-pass filter is usually required to dislodge the interference of a certain wavelength light, which inevitably enhances the weight and increases the cost. Here, we demonstrate a self-powered photodetector with a tunable response range by constructing a heterojunction structure consisting of poly(3-hexylthiophene) (P3HT), a TiO₂ interlayer, and silicon nanowires. By controlling the P3HT concentration, both core-shell and embedded configurations can be obtained, which exhibit different response ranges. This work provides a convenient route to construct self-powered wavelength-selective photodetectors, which may find applications in light communication and biomedical engineering.

Highly Sensitive, Visible Blind, Wearable, and Omnidirectional Near-Infrared Photodetectors

Visible blind near-infrared (NIR) photodetection is essential when it comes to weapons used by military personnel, narrow band detectors used in space navigation systems, medicine, and research studies. The technological field of filterless visible blind, NIR omnidirectional photodetection and wearability is at a preliminary stage. Here, we present a filterless and lightweight design for a visible blind and wearable NIR photodetector capable of harvesting light omnidirectionally. The filterless NIR photodetector comprises the integration of distinct features of lanthanide-doped upconversion nanoparticles (UCNPs), graphene, and micropyramidal poly(dimethylsiloxane) (PDMS) film. The lanthanide-doped UCNPs are designed such that the maximum narrow band detection of NIR is easily accomplished by the photodetector even in the presence of visible light sources. Especially, the 4f ⁿ electronic configuration of lanthanide dopant ions provides for a multilevel hierarchical energy system that provides for longer lifetime of the excited states for photogenerated charge carriers to transfer to the graphene layer. The graphene layer can serve as an outstanding conduction path for photogenerated charge carrier transfer from UCNPs, and the flexible micropyramidal PDMS substrate provides an excellent platform for omnidirectional NIR light detection. Owing to these advantages, a photoresponsivity of ∼800 AW^-1 is achieved by the NIR photodetector, which is higher than the values ever reported by UCNPs-based photodetectors. In addition, the photodetector is stretchable, durable, and transparent, making it suitable for next-generation wearable optoelectronic devices.

A Self-Powered and Flexible Organometallic Halide Perovskite Photodetector with Very High Detectivity

Flexible and self-powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self-powered and flexible PD based on the methylammonium lead iodide (CH₃ NH₃ PBI₃ ) perovskite is demonstrated. Such a self-powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high-quality CH₃ NH₃ PBI₃ perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 10¹³ Jones. In the self-powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW^-1 cm^-2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 ° of illumination. As a result, the self-powered, flexible, 360 ° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real-world sensing capability, suggests a new direction for next-generation optical communications, sensing, and imaging applications.