Van Der Waals Semiconductor Based Omnidirectional Bifacial Transparent Photovoltaic for Visual-Speech Photocommunication.

Omnidirectional photosensing is crucial in optoelectronic devices, enabling a wide field of view (wFoV) and leveraging potential applications for the Internet of Things in sensors, light fidelity, and photocommunication. The wFoV helps overcome the limitations of line-of-sight communication, and transparent photodetection becomes highly desirable as it enables the capture of optical information from various angles. Therefore, developing a photoelectric device with a 360° wFoV, ultra sensitivity to photons, power generation, and transparency is of utmost importance. This study utilizes a heterojunction of van der Waals SnS with Ga2 O3 to fabricate a transparent photovoltaic (TPV) device showing a 360° wFoV with bifacial onsite power production. SnS/Ga2 O3 heterojunction preparation consists of magnetron sputtering and is free from nanopatterning/nanostructuring to achieve the desired wFoV window device. The device exhibits a high average visible transmittance of 56%, generates identical power from bifacial illumination, and broadband fast photoresponse. Careful analysis of the device shows an ultra-sensitive photoinduced defect-modulated heterojunction and photocapacitance, revealed by the impedance spectroscopy, suggesting photon-flux driven charge diffusion. Leveraging the wFoV operation, the TPV embedded visual and speech photocommunication prototype demonstrated, aiming to help visually and auditory impaired individuals, promising an environmental-friendly sustainable future.

Highly Transparent Bidirectional Transparent Photovoltaics for On-Site Power Generators.

If we can transparently produce energy, we may apply invisible power generators to residential architectures to supply energy without losing visibility. Transparent photovoltaic cells (TPVs) are a transparent solar technology that transmits visible light while absorbing the invisible short wavelengths, such as ultraviolet. Installing TPVs in buildings provides an on-site energy supply platform as a window-embedded power generator or color-matched solar cell installation on a building surface. The record-high power generation (10.82 mW) and photocurrent value (68.25 mA) were achieved from large-scale TPVs (25 cm2). The metal oxide heterojunction is the fundamental TPV structure. The high-performance TPVs were achieved by adopting a thin Si film between ZnO and NiO as a functional light-absorbing layer. Based on the large energy band gap of metal oxides, TPVs have a clear transmittance (43%) and good color coordinates, which ensure degrees of freedom to adopt TPV power generators in various colored structures or transparent power windows. The bidirectional feature of TPVs is ultimately desirable to maximize light utilization. TPVs can generate electric power from sunlight during the day and can also work from artificial light sources at night. In the near future, humans will acquire electric power without losing visibility with on-site energy supply platforms.

Transparent Photovoltaics for Self-Powered Bioelectronics and Neuromorphic Applications.

Inspired by the brain, future computation depends on creating a neuromorphic device that is energy-efficient for information processing and capable of sensing and learning. The current computation-chip platform is not capable of self-power and neuromorphic functionality; therefore, a need exists for a new platform that provides both. This Perspective illustrates potential transparent photovoltaics as a platform to achieve scalable, multimodal sensory, self-sustainable neural systems (e.g., visual cortex, nociception, and electronic skin). We present herein a strategy to harvest solar power using a transparent photovoltaic device that provides neuromorphic functionality to implement versatile, sustainable, integrative, and practical applications. The proposed solid-inorganic heterostructure platform is indispensable for achieving a variety of biosensors, sensory systems, neuromorphic computing, and machine learning.

Effects of 3D Printing-Line Directions for Stretchable Sensor Performances.

Health monitoring sensors that are attached to clothing are a new trend of the times, especially stretchable sensors for human motion measurements or biological markers. However, price, durability, and performance always are major problems to be addressed and three-dimensional (3D) printing combined with conductive flexible materials (thermoplastic polyurethane) can be an optimal solution. Herein, we evaluate the effects of 3D printing-line directions (45°, 90°, 180°) on the sensor performances. Using fused filament fabrication (FDM) technology, the sensors are created with different print styles for specific purposes. We also discuss some main issues of the stretch sensors from Carbon Nanotube/Thermoplastic Polyurethane (CNT/TPU) and FDM. Our sensor achieves outstanding stability (10,000 cycles) and reliability, which are verified through repeated measurements. Its capability is demonstrated in a real application when detecting finger motion by a sensor-integrated into gloves. This paper is expected to bring contribution to the development of flexible conductive materials-based on 3D printing.

Transparent photovoltaic memory for neuromorphic device.

Bio-inspired electronic devices have significant potential for use in memory devices of the future, including in the context of neuromorphic computing and architecture. This study proposes a transparent heterojunction device for the artificial human visual cortex. Owing to their high transparency, such devices directly react to incoming light to mimic neurological and biological processes in the nervous system. Metal-oxide materials are applied to form a transparent heterojunction (n-type ZnO/p-type NiO) in the proposed device that also provides the photovoltaic function to realize the optic nerve system. The device also exhibits nociceptive features. Its transparent photovoltaic feature endows it with self-powered operation that ensures long-term reliability without needing to replace the power system. This self-powered and highly transparent visual electronic device can provide a route for sustainable applications of neuromorphic computing, including artificial eyes.

Transparent Stacked Photoanodes with Efficient Light Management for Solar-Driven Photoelectrochemical Cells.

Solar-driven hydrogen generation is one of the most promising approaches for building a sustainable energy system. Photovoltaic-assisted photoanodes can help to reduce the overpotential of water splitting in photoelectrochemical (PEC) cells. Transparent photoanodes can improve light-conversion efficiency by absorbing high-energy photons while transmitting lower energy photons to the photocathode for hydrogen production. In this work, transparent photoanodes were implemented by forming metal-oxide junctions of NiO/TiO2 heterostructures for creating the photovoltaic effect. The photovoltaic-induced transparent photoelectrode (PTPE) provides the photovoltage (0.7 V), which efficiently reduces the onset potential voltage by -0.38 V versus the reversible hydrogen electrode (RHE), as compared to 0.17 V versus RHE for a single-TiO2 photoanode. The PEC cell has a high photocurrent of 1.68 mA at 1.23 V with respect to the RHE. The chemical endurance of metal-oxides maintains the stability of the PTPE for over 100 h in an alkaline electrolyte of 0.1 M KOH. The results of this study reveal that combining multiple PTPE cells to create a stacked photoanode enhances the photocurrent roughly in proportion to the number of PTPE cells. This design scheme for optimizing the light-conversion efficiency in a PTPE-photoanode system is promising for creating robust systems for on-site energy producers.

Physical and chemical data of WS2 platelets and thickness-dependent photoresponses.

In this data article, the properties of WS2/ZnO type-I heterostructure which corresponds to the research article "Vertically trigonal WS2 layer embedded heterostructure for enhanced ultraviolet-visible photodetector" (Nguyen et al., 2018) are presented by characteristics of WS2 layer, diode properties, and thickness dependent photoresponses. The device performances under the effect of rapid thermal processing (RTP) is presented. The WS2 platelets grown by large area sputtering method (Nguyen et al., 2018) was characterized in term of morphology and chemical elements distribution by using transmission electron microscope (TEM), energy dispersive spectroscopy (EDS) and X-Ray photoelectron spectroscopy (XPS). Diode characterization of WS2/ZnO like rectifying ratio, ideal factor and barrier height are presented. The variation of photocurrent of ITO/WS2/ZnO/FTO/glass photodetector, its dependence on the WS2 thickness and influence of post- thermal treatment are presented.

High-performing ultrafast transparent photodetector governed by the pyro-phototronic effect.

In this work we utilized the advantage of the photo-induced pyroelectric effect - known as "Pyro-phototronic" - to design a self-powered, ultrafast, transparent ultraviolet (UV, 365 nm) photodetector. The device architecture contains an UV absorbing pyroelectric ZnO layer sandwiched between hole-selective V2O5 and a bottom ITO electrode. In addition, the device shows a high optical transmittance, >70%, in the entire visible region. The photo current of the device was enhanced from 19 to 42 µA under pulsed UV light illumination (λ = 365 nm, 4 mW cm-2) by exploiting the pyro-phototronic potential. In addition, the photodetector demonstrated ultrafast responses of ∼4 µs for the rise time and ∼16 µs for the fall time. Further, a high photoresponsivity of ∼36.34 mA W-1 and excellent photodetectivity of ∼6.04 × 1014 Jones, with an enhancement of 725% in both due to the pyroelectric potential, were measured. This novel approach will open a new path to design transparent and ultrafast devices, as well as on the flexible substrates, for future optoelectronic applications.