van der Waals Semiconductor Empowered Vertical Color Sensor

Pseudologic Optical Circuit Method for Advanced Color Sensing in IGZO Phototransistor Arrays with Chlorophyll Absorption Layers

Recently, the elimination of color filters has become a key focus in photodetector research because of the potential to create more compact and cost-effective sensor systems. In this study, a novel concept of a filter-free color-discrimination photosensor using an indium gallium zinc oxide (IGZO, In/Ga/Zn = 3.1:2.6:1.0)-based phototransistor with an integrated chlorophyll absorption layer (CAL) and a solution-processed oxide absorption layer (SAL) was developed. Chlorophyll, known for its role in photosynthesis as a natural light absorber, offers distinct characteristics compared to conventional photodetectors (i.e., SAL/IGZO), whereby the photoresponsivity decreases with increasing wavelength. Using the ability of chlorophyll to absorb blue and red light, the proposed CAL/IGZO phototransistor exhibited a higher photoresponsivity to red light than to green light. The device achieved a photoresponsivity of 1570 A/W for red light and 681 A/W for green light, with a photosensitivity of 8.35 × 105 and 8.96 × 104 and a detectivity of 8.47 × 1011 and 6.80 × 1010 Jones, respectively, under an illumination intensity of 1 mW/mm2. Furthermore, by integrating the proposed CAL/IGZO phototransistor with a SAL/IGZO phototransistor, which exhibited a different order of photoresponse across RGB wavelengths, an innovative color-discrimination pixel pseudologic circuit was successfully developed. The capability of this circuit to distinguish colors across various light intensities was validated through experimental data and SPICE simulations, with the output voltage ranges confirmed as -2.61 to -3.51 V for red, 1.56 to 2.69 V for green, and -0.22 to -0.68 V for blue over light intensities from 0.1 to 3 mW/mm2. This innovative approach allows effective color detection without conventional color filters, providing an advanced solution for photodetection technologies.

A Near-Infrared Retinomorphic Device with High Dimensionality Reservoir Expression

Physical reservoir-based reservoir computing (RC) systems for intelligent perception have recently gained attention because they require fewer computing resources. However, the system remains limited in infrared (IR) machine vision, including materials and physical reservoir expression power. Inspired by biological visual perception systems, the study proposes a near-infrared (NIR) retinomorphic device that simultaneously perceives and encodes narrow IR spectral information (at ≈980 nm). The proposed device, featuring core-shell upconversion nanoparticle/poly (3-hexylthiophene) (P3HT) nanocomposite channels, enables the absorption and conversion of NIR into high-energy photons to excite more photo carriers in P3HT. The photon-electron-coupled dynamics under the synergy of photovoltaic and photogating effects influence the nonlinearity and high dimensionality of the RC system under narrow-band NIR irradiation. The device also exhibits multilevel data storage capability (≥8 levels), excellent stability (≥2000 s), and durability (≥100 cycles). The system accurately identifies NIR static and dynamic handwritten digit images, achieving recognition accuracies of 91.13% and 90.07%, respectively. Thus, the device tackles intricate computations like solving second-order nonlinear dynamic equations with minimal errors (normalized mean squared error of 1.06 × 10⁻3 during prediction).

Filter-Less Color-Selective Photodetector Derived from Integration of Parallel Perovskite Photoelectric Response Units

Color-selective photodetectors (PDs) play an indispensable role in spectral recognition, image sensing, and other fields. Nevertheless, complex filters and delicate optical paths in such devices significantly increase their complexity and size, which subsequently impede their integration in smart optoelectronic chips for universal applications. This work demonstrates the successful fabrication of filter-less color-selective perovskite PDs by integrating three perovskite units with different photoresponse on a single chip. The variation in photoresponse is attributed to different quantities of SnO2 nanoparticles, synthesized through controlled ultrasonic treatment on the surface of the electron transportation layer SnS2, which selectively absorb short-wavelength light, thus increasing the relative transmittance of long-wavelength light and enhancing the photoresponse of the units to long wavelengths. By integrating any two units and deriving the formula for the wavelength to the responsivity ratio, a wavelength sensor is developed which can accurately identify incident light in the range of 400-700 nm with a minimum error <3 nm. Furthermore, the device integrating three units with different photoresponse can identify red, green and blue in polychromatic light to achieve color imaging with a relative error <6%. This work provides valuable insights into wavelength identification and color imaging of perovskite PDs.

Additive Manufacturing Provides Infinite Possibilities for Self-Sensing Technology

Integrating sensors and other functional parts in one device can enable a new generation of integrated intelligent devices that can perform self-sensing and monitoring autonomously. Applications include buildings that detect and repair damage, robots that monitor conditions and perform real-time correction and reconstruction, aircraft capable of real-time perception of the internal and external environment, and medical devices and prosthetics with a realistic sense of touch. Although integrating sensors and other functional parts into self-sensing intelligent devices has become increasingly common, additive manufacturing has only been marginally explored. This review focuses on additive manufacturing integrated design, printing equipment, and printable materials and stuctures. The importance of the material, structure, and function of integrated manufacturing are highlighted. The study summarizes current challenges to be addressed and provides suggestions for future development directions.

Covalently-Bonded Laminar Assembly of Van der Waals Semiconductors with Polymers: Toward High-Performance Flexible Devices

Van der Waals semiconductors (vdWS) offer superior mechanical and electrical properties and are promising for flexible microelectronics when combined with polymer substrates. However, the self-passivated vdWS surfaces and their weak adhesion to polymers tend to cause interfacial sliding and wrinkling, and thus, are still challenging the reliability of vdWS-based flexible devices. Here, an effective covalent vdWS-polymer lamination method with high stretch tolerance and excellent electronic performance is reported. Using molybdenum disulfide (MoS2 )and polydimethylsiloxane (PDMS) as a case study, gold-chalcogen bonding and mercapto silane bridges are leveraged. The resulting composite structures exhibit more uniform and stronger interfacial adhesion. This enhanced coupling also enables the observation of a theoretically predicted tension-induced band structure transition in MoS2 . Moreover, no obvious degradation in the devices' structural and electrical properties is identified after numerous mechanical cycle tests. This high-quality lamination enhances the reliability of vdWS-based flexible microelectronics, accelerating their practical applications in biomedical research and consumer electronics.

Hierarchies in Visual Pathway: Functions and Inspired Artificial Vision

The development of artificial intelligence has posed a challenge to machine vision based on conventional complementary metal-oxide semiconductor (CMOS) circuits owing to its high latency and inefficient power consumption originating from the data shuffling between memory and computation units. Gaining more insights into the function of every part of the visual pathway for visual perception can bring the capabilities of machine vision in terms of robustness and generality. Hardware acceleration of more energy-efficient and biorealistic artificial vision highly necessitates neuromorphic devices and circuits that are able to mimic the function of each part of the visual pathway. In this paper, we review the structure and function of the entire class of visual neurons from the retina to the primate visual cortex within reach (Chapter 2) are reviewed. Based on the extraction of biological principles, the recent hardware-implemented visual neurons located in different parts of the visual pathway are discussed in detail in Chapters 3 and 4. Furthermore, valuable applications of inspired artificial vision in different scenarios (Chapter 5) are provided. The functional description of the visual pathway and its inspired neuromorphic devices/circuits are expected to provide valuable insights for the design of next-generation artificial visual perception systems.

Miniaturized spectrometers with a tunable van der Waals junction

Miniaturized computational spectrometers, which can obtain incident spectra using a combination of device spectral responses and reconstruction algorithms, are essential for on-chip and implantable applications. Highly sensitive spectral measurement using a single detector allows the footprints of such spectrometers to be scaled down while achieving spectral resolution approaching that of benchtop systems. We report a high-performance computational spectrometer based on a single van der Waals junction with an electrically tunable transport-mediated spectral response. We achieve high peak wavelength accuracy (∼0.36 nanometers), high spectral resolution (∼3 nanometers), broad operation bandwidth (from ∼405 to 845 nanometers), and proof-of-concept spectral imaging. Our approach provides a route toward ultraminiaturization and offers unprecedented performance in accuracy, resolution, and operation bandwidth for single-detector computational spectrometers.