An Ultrasensitive Bi2O2Se/In2S3 Photodetector with Low Detection Limit and Fast Response toward High-Precision Unmanned Driving.

The machine vision utilized in unmanned driving systems must possess the ability to accurately perceive scenes under low-light illumination conditions. To achieve this, photodetectors with low detection limits and a fast response are essential. Current systems rely on avalanche diodes or lidars, which come with the drawbacks of increased energy consumption and complexity. Here, we present an ultrasensitive photodetector based on a two-dimensional (2D) Bi2O2Se/In2S3 heterostructure, incorporating a homotype unilateral depletion band design. This innovative architecture effectively modulates the transport of both free and photoexcited carriers, suppressing the dark current and facilitating the rapid and efficient separation of photocarriers. Owing to these features, this device exhibits a responsivity of 144 A/W, a specific detectivity of 1.2 × 1014 Jones, and a light on/off ratio of 1.1 × 105. These metrics rank among the top values reported for state-of-the-art 2D devices. Moreover, this device also demonstrates a fast response time of 170/296 µs and a low noise equivalent power of 0.57 fW/Hz1/2, attributes that endow it with ultraweak light imaging capabilities. Furthermore, we have successfully integrated this device into an unmanned driving system, providing a perspective on the design and fabrication of future optoelectronic devices.

Enhancement of photovoltaic parameters of thermally stable graphene/LaVO3semitransparent solar cell by employing interfacial graphene quantum dots.

Semitransparent solar cells are attracting attention not only for their visual effects but also for their ability to effectively utilize solar energy. Here, we demonstrate a translucent solar cell composed of bis(trifluoromethane sulfonyl)-amide (TFSA)-doped graphene (Gr), graphene quantum dots (GQDs), and LaVO3. By introducing a GQDs intermediate layer at the TFSA-Gr/LaVO3interface, we can improve efficiency by preventing carrier recombination and promoting charge collection/separation in the device. As a result, the efficiency of the GQDs-based solar cell was 4.35%, which was higher than the 3.52% of the device without GQDs. Furthermore, the average visible transmittance of the device is 28%, making it suitable for translucent solar cells. The Al reflective mirror-based system improved the power conversion efficiency by approximately 7% compared to a device without a mirror. Additionally, the thermal stability of the device remains at 90% even after 2000 h under an environment with a temperature of 60 °C and 40% relative humidity. These results suggest that TFSA-Gr/GQDs/LaVO3-based cells have a high potential for practical use as a next-generation translucent solar energy power source.

Graphene-PbS Quantum Dot Heterostructure for Broadband Photodetector with Enhanced Sensitivity.

Photodetectors converting light into electrical signals are crucial in various applications. The pursuit of high-performance photodetectors with high sensitivity and broad spectral range simultaneously has always been challenging in conventional semiconductor materials. Graphene, with its zero bandgap and high electron mobility, is an attractive candidate, but its low light absorption coefficient restricts its practical application in light detection. Integrating graphene with light-absorbing materials like PbS quantum dots (QDs) can potentially enhance its photodetection capabilities. Here, this work presents a broadband photodetector with enhanced sensitivity based on a graphene-PbS QD heterostructure. The device leverages the high carrier mobility of graphene and the strong light absorption of PbS QDs, achieving a wide detection range from ultraviolet to near-infrared. Employing a simple spinning method, the heterostructure demonstrates ultrahigh responsivity up to the order of 107 A/W and a specific detectivity on the order of 1013 Jones, showcasing significant potential for photoelectric applications.

One-Dimensional ZnO Nanorod Array Grown on Ag Nanowire Mesh/ZnO Composite Seed Layer for H2 Gas Sensing and UV Detection Applications.

Photodetectors and gas sensors are vital in modern technology, spanning from environmental monitoring to biomedical diagnostics. This paper explores the UV detection and gas sensing properties of a zinc oxide (ZnO) nanorod array (ZNA) grown on silver nanowire mesh (AgNM) using a hydrothermal method. We examined the impact of different zinc acetate precursor concentrations on their properties. Results show the AgNM forms a network with high transparency (79%) and low sheet resistance (7.23 Ω/□). A sol-gel ZnO thin film was coated on this mesh, providing a seed layer with a hexagonal wurtzite structure. Increasing the precursor concentration alters the diameter, length, and area density of ZNAs, affecting their performance. The ZNA-AgNM-based photodetector shows enhanced dark current and photocurrent with increasing precursor concentration, achieving a maximum photoresponsivity of 114 A/W at 374 nm and a detectivity of 6.37 × 1014 Jones at 0.05 M zinc acetate. For gas sensing, the resistance of ZNA-AgNM-based sensors decreases with temperature, with the best hydrogen response (2.71) at 300 °C and 0.04 M precursor concentration. These findings highlight the potential of ZNA-AgNM for high-performance UV photodetectors and hydrogen gas sensors, offering an alternative way for the development of future sensing devices with enhanced performance and functionality.

ß-Ga2O3 Nanoribbon with Ultra-High Solar-Blind Ultraviolet Polarization Ratio.

Solar-blind ultraviolet (UV) detection plays a critical role in imaging and communication due to its low-noise background, high signal-to-noise ratio, and strong anti-interference capabilities. Detecting the polarization state of UV light can enhance image information and expand the communication dimension. Although polarization detection is explored in visible and infrared light, and applied in fields such as astrophysics and submarine seismic wave detection, solar-blind UV polarization detection remains largely unreported. This is primarily due to the challenge of creating UV polarizers with high transmittance, high extinction ratio, and strong resistance to UV radiation. In this study, it is discovered that the space symmetry breaking of the ß-Ga2O3's b-c plane results in a significant optical absorption dichroic ratio. Leveraging ß-Ga2O3's high solar-blind UV response, a lensless solar-blind UV polarization-sensitive photodetector, circumventing the challenges associated with solar-blind UV polarizers is designed. This photodetector exhibits an exceptionally high intrinsic polarization ratio under 254 nm linearly polarized light, approximately two orders of magnitude higher than other reported nanomaterial-based polarization-sensitive photodetectors. Additionally, it demonstrates significant advantages in solar-blind UV imaging and light communication. This work introduces a novel strategy for solar-blind ultraviolet polarization detection and offers a promising approach for solar-blind light communication.

2D Printed Plasmonic Nanoparticle Array Incorporated Formamidinium-Based High-Performance Self-Biased Perovskite Photodetector.

Utilizing noble metal nanoparticles through novel technologies is a promising avenue for enhancing the performance of organic/inorganic photodetectors. This study investigates the performance enhancement of Formamidinium-based perovskite (Pe) photodetectors (PDs) through the incorporation of plasmonic silver nanoparticles (Ag NPs) arrays using a 2D printing technique. The incorporation of plasmonic Ag NPs leads to a major improvement in the performance of the planar PD device, which is attributed to increased light absorption, hot electron generation, and more efficient charge extraction and transport. The unique aspect of this study lies in the method of incorporating plasmonic NPs using a two-dimensional printing technology. This approach offers several advantages over traditional methods, including lower cost, nonvacuum operation, and compatibility with room temperature fabrication. The printed plasmon-enhanced optimized perovskite PD exhibits remarkable performance metrics, including a peak responsivity of 1.03 A/W at 5 V external bias, which is significantly high compared to the reported devices. Moreover, the PD demonstrates exceptional detectivity with a peak value of 3.7 × 1012 Jones at 5 V, highlighting its capability to detect ultralow light signals with high precision. The device can be reversibly switched between low and high conductance states, yielding a stable and repeatable Ilight/Idark ratio of 1.06 × 104. In addition, the integration of plasmonic nanoparticles imparts remarkable photovoltaic characteristics to the perovskite photodetector, enabling it to function as a self-biased device. The hybrid device demonstrates a peak responsivity of 15 mA/W, a high detectivity of 2.15 × 1011 Jones, and a significant on-off ratio of 2.23 × 103, all achieved at zero external bias. Overall, this study presents a significant advancement in the field of plasmon-enhanced Pe photodetection technology. By utilizing the benefits of printing technology to incorporate NPs, we have developed a high-performance PD that combines cost-effectiveness with exceptional performance. Thus, we believe that this study will pave the way for the development of a low-cost, high-performance plasmon-enhanced Pe-based PD.

Inorganic Semiconductor-Based Flexible UV Photodetector Arrays Achieved by Specific Flip-Chip Bonding.

In recent years, flexible UV photodetectors (PDs) with complex environmental adaptability and great wearability have attracted the attention of researchers worldwide. Wide bandgap inorganic semiconductor materials with excellent optoelectronic properties and mechanical stability are key functional materials for UV PD devices. However, the high temperature processing and inherent brittleness limit the further application of high-quality inorganic semiconductors in the field of flexible optoelectronics. In this work, we develop a specific flip-chip bonding fabrication technique that utilizes high-temperature treated inorganic semiconductor materials for high-performance flexible UV detection devices. Leveraging this technique, a 7 × 7 pixel flexible UV photodetector array (UV-FPDA) device based on a vertical architecture Mg-doped ZnO/NiO (Mg:ZnO/NiO) heterojunction transistor is built. The UV-FPDAs exhibit a high responsivity of 75.8 A/W and an outstanding detectivity of 8.5 × 1012 Jones. Besides, the UV-FPDAs also demonstrate excellent bending stability. Furthermore, the photoresponse characteristics of each pixel are trained and learned by an artificial neural network to achieve clear imaging of UV light information. Our results provide a new pathway for the application of inorganic semiconductors in the field of high-performance flexible UV photodetection.

Graphene-Templated Achiral Hybrid Perovskite for Circularly Polarized Light Sensing.

This study points out the importance of the templating effect in hybrid organic-inorganic perovskite semiconductors grown on graphene. By combining two achiral materials, we report the formation of a chiral composite heterostructure with electronic band splitting. The effect is observed through circularly polarized light emission and detection in a graphene/α-CH(NH2)2PbI3 perovskite composite, at ambient temperature and without a magnetic field. We exploit the spin-charge conversion by introducing an unbalanced spin population through polarized light that gives rise to a spin photoconductive effect rationalized by Rashba-type coupling. The prepared composite heterostructure exhibits a circularly polarized photoluminescence anisotropy gCPL of ∼0.35 at ∼2.54 × 103 W cm-2 confocal power density of 532 nm excitation. A carefully engineered interface between the graphene and the perovskite thin film enhances the Rashba field and generates the built-in electric field responsible for photocurrent, yielding a photoresponsivity of ∼105 A W-1 under ∼0.08 µW cm-2 fluence of visible light photons. The maximum photocurrent anisotropy factor gph is ∼0.51 under ∼0.16 µW cm-2 irradiance. The work sheds light on the photophysical properties of graphene/perovskite composite heterostructures, finding them to be a promising candidate for developing miniaturized spin-photonic devices.

The Light Wavelength, Intensity, and Biasing Voltage Dependency of the Dark and Photocurrent Densities of a Solution-Processed P3HT:PC61BM Photodetector for Sensing Applications.

The promising possibility of an organic photodetector (OPD) is emerging in the field of sensing applications for its tunable absorption range, flexibility, and large-scale fabrication abilities. In this work, we fabricated a bulk heterojunction OPD with a device structure of glass/ITO/PEDOT:PSS/P3HT:PC61BM/Al using the spin-coating process and characterized the dark and photocurrent densities at different applied bias conditions for red, green, and blue incident LEDs. The OPD photocurrent density exhibited a magnitude up to 2.5-3 orders higher compared to the dark current density at a -1 V bias while it increased by up to 3-4 orders at zero bias conditions for red, green, and blue lights, showing an increasing trend when a higher voltage is applied in the negative direction. Different OPD inner periphery shapes, the OPD to LED distance, and OPD area were also considered to bring the variation in the OPD dark and photocurrent densities, which can affect the on/off ratio of the OPD-LED hybrid system and is a critical phenomenon for any sensing application.

Recent Progress on Layered Sn and Pb-Based Mono Chalcogenides: Synthesis, Structure, Optical, and Thermoelectric Properties and Related Applications.

The research on two-dimensional materials has gained significant traction due to their potential for thermoelectric, optical, and other properties. The development of two-dimensional (2D) nanostructured-based TE generators and photodetectors has shown promising results. Over the years, researchers have played a crucial role in advancing this field, enhancing the properties of 2D materials through techniques such as doping, alloying, and various growth methods. Among these materials, black phosphorus, transition metal dichalcogenides, graphene, and IVA-VIA compounds stand out for their remarkable electronic, mechanical, and optical properties. This study presents a comprehensive review of the progress in the field, focusing on IVA-VIA compounds and their applications in TE and photodetector technologies. We summarize recent advancements in enhancing these materials' TE and optical properties and provide an overview of various synthesis techniques for their fabrication. Additionally, we highlight their potential applications as photodetectors in the infrared spectrum. This comprehensive review aims to equip researchers with a deep understanding of the TE and optical properties of 2DMs and their potential applications and to inspire further advancements in this field of research.

Advances in Group-10 Transition Metal Dichalcogenide PdSe2-Based Photodetectors: Outlook and Perspectives.

The recent advancements in low-dimensional material-based photodetectors have provided valuable insights into the fundamental properties of these materials, the design of their device architectures, and the strategic engineering approaches that have facilitated their remarkable progress. This review work consolidates and provides a comprehensive review of the recent progress in group-10 two-dimensional (2D) palladium diselenide (PdSe2)-based photodetectors. This work first offers a general overview of the various types of PdSe2 photodetectors, including their operating mechanisms and key performance metrics. A detailed examination is then conducted on the physical properties of 2D PdSe2 material and how these metrics, such as structural characteristics, optical anisotropy, carrier mobility, and bandgap, influence photodetector device performance and potential avenues for enhancement. Furthermore, the study delves into the current methods for synthesizing PdSe2 material and constructing the corresponding photodetector devices. The documented device performances and application prospects are thoroughly discussed. Finally, this review speculates on the existing trends and future research opportunities in the field of 2D PdSe2 photodetectors. Potential directions for continued advancement of these optoelectronic devices are proposed and forecasted.

Ternary TiO2/MoS2/ZnO hetero-nanostructure based multifunctional sensing devices.

Novel sensing applications benefit from multifunctional nanomaterials responsive to various external stimuli such as mechanics, electricity, light, humidity, or pollution. While few such materials occur naturally, the careful design of synergized nanomaterials unifies the cross-coupled properties which are weak or absent in single-phase materials. In this study, 2D MoS2 integrated with ultrathin dielectric oxide layers forms hetero-nanostructures with significant impacts on carrier transport. The ternary TiO2/MoS2/ZnO hetero-nanostructures, along with their individual properties, improve the performance of multifunctional sensing devices. The synthesized hetero-nanostructure exhibits a responsivity of up to 16 mA/W to 700 nm light and responds to 5 ppm ammonia gas at room temperature. These enhancements are attributed to interface charge transfer and photogating effects. The ternary TiO2/MoS2/ZnO hetero-nanostructure is compatible with existing semiconductor fabrication technologies, making it feasible to integrate into flexible, lightweight semiconductor devices and circuits. These results may inspire new photodetectors and sensing devices based on two-dimensional (2D) layered materials for IoT applications.

Self-Driven Perovskite/Organic Quasi-Tandem Photodetectors Operating in Both Narrowband and Broadband Regimes.

Dual-band photodetectors (PDs) have attracted extensive research attention due to their great potential for diverse and refreshing application scenarios in full-color imaging, optical communication, and imaging detection. Here, a self-driven dual-band PD without filters and other auxiliary equipment to achieve a narrowband response in Mode 1 and a broadband response in Mode 2 was designed based on carrier-selective transmission narrowing (CSTN). The polymer material poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), which has the appropriate energy level, was selected to be the carrier-selective transmission layer. In Mode 1, the dual-band PD exhibits a near-infrared (NIR) narrowband response in 750-900 nm, which indicates a responsivity of 360 mA/W, a full-width at half-maximum (fwhm) of 81 nm, and a specific detectivity (D*) of 7.49 × 1010 Jones at 810 nm. Simultaneously, in Mode 2, the dual-band PD exhibits a UV-visible-NIR broadband responsivity of 180 mA/W and a specific detectivity (D*) of 3.8 × 1010 Jones at 520 nm. Our study provides a reliable idea for the commercial applications of dual-function photodetectors.

Ultrafast Response and Broad Detection Range of a Ternary Cation Perovskite Single-Crystal Thin Film Photodetector for Imaging.

FA-MA-Cs ternary cation perovskite exhibits excellent optoelectronic properties and high stabilities against humidity and light soaking and thus has aroused extensive attention in polycrystalline thin film solar cells. Compared with polycrystalline counterparts, FA-MA-Cs ternary cation perovskite single-crystal thin films (SCTFs) have lower defects, better carrier transport capacity, and stability because of lacking grain boundary defects. However, the immature growth technology of SCTFs restricts digging out its optoelectronic potential. Here, we proposed an improved space-confined method to grow large area FA0.9 MA0.05Cs0.05PbI2.7Br0.3 SCTFs using a tunable heating area to control the nucleation and growth process. Its area reaches 64 mm2 with a thickness of 26 µm. The SCTF exhibits high crystallinity, low defect density, long carrier lifetime, and high moisture resistance stability. Besides, a photosensitive chip based on a planar metal-semiconductor-metal photodetector demonstrates linear response to the three primary colors, with a photosensitive range that is 1.5 times that of protocol 3 wide color gamut. Under high-frequency light sources, the on/off ratio reaches 3.9 × 103, and the response time can be as low as 400 ns. Such ultrafast response speed and broad photosensitive range are successfully achieved for imaging applications.

Ultrathin Ga2O3 Photodetector with Fast Response and Trajectory Tracking Capability Fabricated by Liquid Metal Oxidation.

Low-dimensional Ga2O3 demonstrates a unique ultraviolet photoresponse and could be used in various electronic and optical systems. However, the low-dimensional Ga2O3 photodetector is faced with the challenges of a complex preparation process and poor device performance. In this work, ultrathin Ga2O3 layers with ∼7 nm thickness are prepared on quartz rods by UV exposure to liquid gallium. Benefiting from low-density oxygen vacancy defects cured by UV exposure, the low-dimensional Ga2O3 photodetector exhibits a high response speed (rise: 64.7 µs; fall: 51.4 µs) and an exceptional linear dynamic range of 120 dB. Furthermore, the photodetector array based on these ultrathin Ga2O3 shows an effective trajectory tracking capability by monitoring UV source motion. This work develops a simple preparation method to construct a low-dimensional UV photodetector array with fast response and useful trajectory tracking capability, exhibiting the significance of ultrathin Ga2O3 in UV optoelectronics.

Facile synthesis of Bi2ZnB2O7-MoS2nanocomposite for photodetector and photocatalytic Rhodamine B dye degradation application.

In this research, the visible light active performance of Bi2ZnB2O7(BBZO) was significantly enhanced through the formation of a composite with few layer MoS2. The resultant MoS2@BBZO catalyst was employed in both photocatalysis and photodetector applications. Comprehensive structural and morphological analyses of the MoS2@BBZO catalyst were conducted using x-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy. The estimated band gaps of BBZO and the composite were found to be 2.8 eV and 1.74 eV, respectively. Rhodamine B degradation studies demonstrated that the catalyst achieved 75% degradation within 30 min. Additionally, the photodetector application was investigated, revealing rapid photo-switching capabilities and an increased photocurrent.

High-Performance CsPbI3 Quantum Dot Photodetector with a Vertical Structure Based on the Frenkel-Poole Emission Effect.

The selection of photoactive materials and the design of device structures are critical to the photoelectronic performance of photodetectors. This study reports on a vertically structured photodetector device with rapid, stable, and efficient photoelectric performance across the UV-visible broadband range based on the Si++/SiO2/Au/single-layer graphene/CsPbI3 quantum dots (QDs) configuration. In this specific device structure, a relatively high conductivity Si++/SiO2 wafer was used as the substrate, a CsPbI3 QD film with high light absorption was used as the photoactive layer, and a monolayer graphene with high conductivity was inserted between the substrate and the CsPbI3 QD film to form a heterojunction with the QD film. Based on the Frenkel-Poole emission effect arising from the high trap state density within the SiO2 layer, the device exhibited excellent photoelectric performances. Especially at a wavelength of 365 nm, a photocurrent responsivity of 2319 A/W, a specific detectivity of 1.15 × 1014 Jones, an external quantum efficiency of 7883%, and an on/off time of 39/36 ms at a Si++ terminal voltage of -80 V and an optical power density of 84.03 nW/cm2 can be achieved.

Narrowband Solar-Blind Photodetection of the Plasmonic (In0.3Ga0.7)2O3 Detector via the Synergetic Enhancement of Small-Sized Ag-Nanoparticle Photoabsorbance and Surface Modification.

Currently, research on Ag nanoparticles (AgNPs) predominantly focuses on UV/visible photodetection and UV emission, seemingly overlooking the significance of Ag in enhancing deep ultraviolet photon detection. In this work, (In0.3Ga0.7)2O3 thin films were fabricated by plasma-enhanced chemical vapor deposition. Due to the unique photoabsorbance characteristic and better interaction with photons of small-sized AgNPs, they effectively suppress the UVB absorbance caused by energy band engineering in the (In0.3Ga0.7)2O3 thin film while enhancing photoabsorbance in UVC due to the surface plasmon effect. Therefore, under the synergistic effect of enhanced photon absorbance and hot electron transfer, the performance of the detector is significantly improved, and its responsivity (R), external quantum efficiency, and detectivity (D*) are 193 mA/W, approximately 100%, and 1014 Jones, respectively, at a bias of -6 V. The fast response time and decay time are 634.6 and 194.1 ms, respectively; the rapid decay facilitated by AgNPs is attributed to the increased indirect recombination rate. AgNPs exhibit excellent narrowband response characteristics and absorbance properties in specific wavelength bands for the InGaO photodetector. This research lays the foundation for the practical application of localized surface plasmon resonance-enhanced photon-sensing capabilities.

Modulating Eco-friendly Colloidal AgGaS2 Quantum Dots for Highly Efficient Photodetection and Image Sensing via Direct Growth of Ternary AgInS2 Shell.

Tailoring the optoelectronic characteristics of colloidal quantum dots (QDs) by constructing a core/shell structure offers the potential to achieve high-performing solution-processed photoelectric conversion and information processing applications. In this work, the direct growth of wurtzite ternary AgInS2 (AIS) shell on eco-friendly AgGaS2 (AGS) core QDs is realized, giving rise to broadened visible light absorption, prolonged exciton lifetime and enhanced photoluminescence quantum yield (PLQY). Ultrafast transient absorption spectroscopy demonstrats that the photoinduced carrier separation and transfer kinetics of AGS QDs are significantly optimized following the AIS shell coating. As-synthesized environmentally benign AGS/AIS core/shell QDs are employed to fabricate photodetectors (PDs), showing a remarkable responsivity of 38.4 A W-1 and a detectivity of 2.4 × 1012 Jones under visible light illumination (405 nm). Moreover, the fabricated QDs-PDs exhibit superior image-sensing capability to record complex patterns with high resolution (160 × 160 pixels) under visible light illumination at 405 and 532 nm. The findings indicate that the direct growth of multinary narrow-band shell materials on eco-friendly QDs holds great promise to implement future "green", cost-effective and high-performance optoelectronic sensing/imaging systems.

Low-Symmetry Van der Waals Dielectric GaInS3 Triggered 2D MoS2 Giant Anisotropy via Symmetry Engineering.

Low-symmetry structures in van der Waals materials have facilitated the advancement of anisotropic electronic and optoelectronic devices. However, the intrinsic low symmetry structure exhibits a small adjustable anisotropy ratio (1-10), which hinders its further assembly and processing into high-performance devices. Here, a novel 2D anisotropic dielectric, GaInS3 (GIS), which induces isotropic MoS2 to exhibit significant anisotropic optical and electrical responses is demonstrated. With the excellent gate modulation ability of 2D GIS (dielectric constant k ∼12), MoS2 field effect transistor (FET) shows an adjustable conductance ratio from isotropic to anisotropic under dual-gate modulation, up to 106. Theoretical calculations indicate that anisotropy originates from lattice mismatch-induced charge density deformation at the interface. Moreover, the MoS2/GIS photodetector demonstrates high responsivity (≈4750 A W-1) and a large dichroic ratio (≈167). The anisotropic van der Waals dielectric GIS paves the way for the development of 2D transition metal dichalcogenides (TMDCs) in the fields of anisotropic photonics, electronics, and optoelectronics.