scispace - formally typeset
Search or ask a question
Author

Zhenyang Xia

Bio: Zhenyang Xia is an academic researcher from University of Wisconsin-Madison. The author has contributed to research in topics: Radiative cooling & Condensation. The author has an hindex of 7, co-authored 15 publications receiving 251 citations. Previous affiliations of Zhenyang Xia include State University of New York System.

Papers
More filters
Journal ArticleDOI
TL;DR: An origami-inspired approach that enables planar silicon-based photodetector arrays to reshape into concave or convex geometries is shown.
Abstract: Digital image sensors in hemispherical geometries offer unique imaging advantages over their planar counterparts, such as wide field of view and low aberrations. Deforming miniature semiconductor-based sensors with high-spatial resolution into such format is challenging. Here we report a simple origami approach for fabricating single-crystalline silicon-based focal plane arrays and artificial compound eyes that have hemisphere-like structures. Convex isogonal polyhedral concepts allow certain combinations of polygons to fold into spherical formats. Using each polygon block as a sensor pixel, the silicon-based devices are shaped into maps of truncated icosahedron and fabricated on flexible sheets and further folded either into a concave or convex hemisphere. These two electronic eye prototypes represent simple and low-cost methods as well as flexible optimization parameters in terms of pixel density and design. Results demonstrated in this work combined with miniature size and simplicity of the design establish practical technology for integration with conventional electronic devices.

148 citations

Journal ArticleDOI
TL;DR: A high-yield and high-throughput method is used to demonstrate nanometer-thin photodetectors with significantly enhanced light absorption based on nanocavity interference mechanism, which exhibit unique optoelectronic properties, such as the strong field effect and spectral selectivity.
Abstract: Miniaturization of optoelectronic devices offers tremendous performance gain. As the volume of photoactive material decreases, optoelectronic performance improves, including the operation speed, the signal-to-noise ratio, and the internal quantum efficiency. Over the past decades, researchers have managed to reduce the volume of photoactive materials in solar cells and photodetectors by orders of magnitude. However, two issues arise when one continues to thin down the photoactive layers to the nanometer scale (for example, <50 nm). First, light-matter interaction becomes weak, resulting in incomplete photon absorption and low quantum efficiency. Second, it is difficult to obtain ultrathin materials with single-crystalline quality. We introduce a method to overcome these two challenges simultaneously. It uses conventional bulk semiconductor wafers, such as Si, Ge, and GaAs, to realize single-crystalline films on foreign substrates that are designed for enhanced light-matter interaction. We use a high-yield and high-throughput method to demonstrate nanometer-thin photodetectors with significantly enhanced light absorption based on nanocavity interference mechanism. These single-crystalline nanomembrane photodetectors also exhibit unique optoelectronic properties, such as the strong field effect and spectral selectivity.

74 citations

Journal ArticleDOI
TL;DR: A CMOS-compatible, nanostructured, thin junction structure can make use of tailored light trapping to break the trade-off between photon detection efficiency and timing jitter in silicon single-photon avalanche detectors.
Abstract: Silicon single-photon avalanche detectors are becoming increasingly significant in research and in practical applications due to their high signal-to-noise ratio, complementary metal oxide semiconductor compatibility, room temperature operation, and cost-effectiveness. However, there is a trade-off in current silicon single-photon avalanche detectors, especially in the near infrared regime. Thick-junction devices have decent photon detection efficiency but poor timing jitter, while thin-junction devices have good timing jitter but poor efficiency. Here, we demonstrate a light-trapping, thin-junction Si single-photon avalanche diode that breaks this trade-off, by diffracting the incident photons into the horizontal waveguide mode, thus significantly increasing the absorption length. The photon detection efficiency has a 2.5-fold improvement in the near infrared regime, while the timing jitter remains 25 ps. The result provides a practical and complementary metal oxide semiconductor compatible method to improve the performance of single-photon avalanche detectors, image sensor arrays, and silicon photomultipliers over a broad spectral range.

62 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed daytime radiative condensers that can produce water from vapor under direct sunlight, without active consumption of energy, which can substantially increase the performance of passive vapor condensation, which could be used for passive water extraction and purification technologies.
Abstract: A radiative vapor condenser sheds heat in the form of infrared radiation and cools itself to below the ambient air temperature to produce liquid water from vapor This effect has been known for centuries, and is exploited by some insects to survive in dry deserts Humans have also been using radiative condensation for dew collection However, all existing radiative vapor condensers must operate during the nighttime Here, we develop daytime radiative condensers that continue to operate 24 h a day These daytime radiative condensers can produce water from vapor under direct sunlight, without active consumption of energy Combined with traditional passive cooling via convection and conduction, radiative cooling can substantially increase the performance of passive vapor condensation, which can be used for passive water extraction and purification technologies

56 citations

Proceedings ArticleDOI
09 Sep 2019
TL;DR: In this paper, the authors developed a daytime radiative condenser that reflects almost all solar radiation, and can thus create dew water even in direct sunlight, and compared to state-of-the-art condensers, their daytime condenser doubled the production of purified water over a 24-hour period.
Abstract: Vapor condensation plays a crucial role in solar water-purification technologies. Conventional condensers in solar water-purification systems do not provide sufficient cooling power for vapor condensation, limiting the water production rate to 0.4 L m-2 hour-1. On the other hand, radiative dew condensation, a technique used by existing radiative dew condensers, only works at nighttime and is incompatible with solar water-purification technologies. Here, we develop daytime radiative condensers that reflect almost all solar radiation, and can thus create dew water even in direct sunlight. Compared to stateof- art condensers, our daytime radiative condenser doubles the production of purified water over a 24-hour period.

20 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: A discussion of the strategies in materials innovation and structural design to build soft electronic devices and systems is provided and perspectives on the key challenges and future directions of this field are presented.
Abstract: Soft electronics are intensively studied as the integration of electronics with dynamic nonplanar surfaces has become necessary. Here, a discussion of the strategies in materials innovation and structural design to build soft electronic devices and systems is provided. For each strategy, the presentation focuses on the fundamental materials science and mechanics, and example device applications are highlighted where possible. Finally, perspectives on the key challenges and future directions of this field are presented.

417 citations

Journal ArticleDOI
TL;DR: The recent advances in stretchable conductors based on the percolation networks of nanoscale conductive fillers in elastomeric media are summarized and various techniques that are used to reduce the contact resistance between the conductive filler materials are highlighted.
Abstract: Highly conductive and intrinsically stretchable electrodes are vital components of soft electronics such as stretchable transistors and circuits, sensors and actuators, light-emitting diode arrays, and energy harvesting devices. Many kinds of conducting nanomaterials with outstanding electrical and mechanical properties have been integrated with elastomers to produce stretchable conductive nanocomposites. Understanding the characteristics of these nanocomposites and assessing the feasibility of their fabrication are therefore critical for the development of high-performance stretchable conductors and electronic devices. We herein summarise the recent advances in stretchable conductors based on the percolation networks of nanoscale conductive fillers in elastomeric media. After discussing the material-, dimension-, and size-dependent properties of conductive fillers and their implications, we highlight various techniques that are used to reduce the contact resistance between the conductive filler materials. Furthermore, we categorize elastomer matrices with different stretchabilities and mechanical properties based on their polymeric chain structures. Then, we discuss the fabrication techniques of stretchable conductive nanocomposites toward their use in soft electronics. Finally, we provide representative examples of stretchable device applications and conclude the review with a brief outlook for future research.

347 citations

Journal ArticleDOI
20 May 2020-Nature
TL;DR: A biomimetic electrochemical eye is presented that has a hemispherical retina made from a high-density array of perovskite nanowires that are sensitive to light, mimicking the photoreceptors of a biological retina.
Abstract: Human eyes possess exceptional image-sensing characteristics such as an extremely wide field of view, high resolution and sensitivity with low aberration1. Biomimetic eyes with such characteristics are highly desirable, especially in robotics and visual prostheses. However, the spherical shape and the retina of the biological eye pose an enormous fabrication challenge for biomimetic devices2,3. Here we present an electrochemical eye with a hemispherical retina made of a high-density array of nanowires mimicking the photoreceptors on a human retina. The device design has a high degree of structural similarity to a human eye with the potential to achieve high imaging resolution when individual nanowires are electrically addressed. Additionally, we demonstrate the image-sensing function of our biomimetic device by reconstructing the optical patterns projected onto the device. This work may lead to biomimetic photosensing devices that could find use in a wide spectrum of technological applications. A biomimetic electrochemical eye is presented that has a hemispherical retina made from a high-density array of perovskite nanowires that are sensitive to light, mimicking the photoreceptors of a biological retina.

287 citations

Journal ArticleDOI
Sa Cai1, Xiaojie Xu1, Wei Yang1, Jiaxin Chen1, Xiaosheng Fang1 
TL;DR: The fundamental design principles of turning "hard" photodetectors "soft," including 2D (polymer and paper substrate-based devices) and 1D PDs (fiber shaped devices) are summarized, which serve as the roadmap for future exploration in wearable PDs in various applications, including health monitoring and Internet of Things.
Abstract: Photodetectors (PDs), as an indispensable component in electronics, are highly desired to be flexible to meet the trend of next-generation wearable electronics. Unfortunately, no in-depth reviews on the design strategies, material exploration, and potential applications of wearable photodetectors are found in literature to date. Thus, this progress report first summarizes the fundamental design principles of turning "hard" photodetectors "soft," including 2D (polymer and paper substrate-based devices) and 1D PDs (fiber shaped devices). In short, the flexibility of PDs is realized through elaborate substrate modification, material selection, and device layout. More importantly, this report presents the current progress and specific requirements for wearable PDs according to the application: monitoring, imaging, and optical communication. Challenges and future research directions in these fields are proposed at the end. The purpose of this progress report is not only to shed light on the basic design principles of wearable PDs, but also serve as the roadmap for future exploration in wearable PDs in various applications, including health monitoring and Internet of Things.

242 citations

Journal ArticleDOI
TL;DR: In this paper, the recent developments in silicon-compatible photodetectors, both in device advances and their integration routes, are reviewed and possible future directions in this field are discussed and concluded.
Abstract: Encouraged by the increasing requirements of intelligent equipment, silicon integrated circuit–compatible photodetectors that support single-chip photonic–electronic systems have gained considerable progresses. Advanced materials have resulted in enhanced device performance based on traditional photovoltaic effect and photoconductive effect, and novel device designs have catalyzed new working mechanisms combing rapid photoresponse and high responsivity gain. Surprising applications are developed using monolithic photonic–electronic platforms, and the developing integration strategies keep pace with the developing complementary metal-oxide-semiconductor techniques as well as nonsilicon substrates. Here, the recent developments in silicon-compatible photodetectors, both in device advances and their integration routes, are reviewed. Meanwhile, the progresses, challenges, and possible future directions in this field are discussed and concluded.

195 citations