Human eyes possess exceptional image sensing characteristics such as spectacularly wide field of view (FOV), high resolution and sensitivity with low aberration. Biomimetic eyes with the same superior characteristics are highly desirable in many technological applications. However, the spherical nature of biological eyes, particularly the core component of retina, poses an enormous challenge for fabrication of biomimetic eyes. Herein, we demonstrate a unique biomimetic electrochemical eye using a hemispherical retina made of high-density array of nanowires mimicking photoreceptors on a real retina. The device design has a high degree of structural similarity to a real human eye with potency to achieve a high imaging resolution when individual nanowires are electrically addressed. Meanwhile, image sensing function of our biomimetic eye device is also demonstrated. The work here may lead to a new generation of photosensing and imaging devices based on a bioinspired design that can benefit a wide spectrum of technological applications.

Large-scale and highly ordered 3D perov-skite nanowire (NW) arrays are achieved in nanoengineering templates by a unique vapor-solid-solid reaction process. The excellent material properties, in conjunction with the high integration density of the NW arrays, make them promising for 3D integrated nanoelectronics/optoelectronics. Image sensors with 1024 pixels are assembled and characterized to demonstrate the technological potency.

Organometal halide perovskite materials have triggered enormous attention for a wide range of high-performance optoelectronic devices. However, their stability and toxicity are major bottleneck challenges for practical applications. Substituting toxic heavy metal, that is, lead (Pb), with other environmentally benign elements, for example, tin (Sn), could be a potential solution to address the toxicity issue. Nevertheless, even worse stability of Sn-based perovskite material than Pb-based perovskite poses a great challenge for further device fabrication. In this work, for the first time, three-dimensional CHNHSnI perovskite nanowire arrays were fabricated in nanoengineering templates, which can address nanowire integration and stability issues at the same time. Also, nanowire photodetectors have been fabricated and characterized. Intriguingly, it was discovered that as the nanowires are embedded in mechanically and chemically robust templates, the material decay process has been dramatically slowed down by up to 840 times, as compared with a planar thin film. This significant improvement on stability can be attributed to the effective blockage of diffusion of water and oxygen molecules within the templates. These results clearly demonstrate a new and alternative strategy to address the stability issue of perovskite materials, which is the major roadblock for high-performance optoelectronics.

Alluring optical and electronic properties have made organometallic halide perovskites attractive candidates for optoelectronics. Among all perovskite materials, inorganic CsPbX (X is halide) in black cubic phase has triggered enormous attention recently owing to its comparable photovoltaic performance and high stability as compared to organic and hybrid perovskites. However, cubic phase stabilization at room temperature for CsPbI still survives as a challenge. Herein we report all inorganic three-dimensional vertical CsPbI perovskite nanowires (NWs) synthesized inside anodic alumina membrane (AAM) by chemical vapor deposition (CVD) method. It was discovered that the as-grown NWs have stable cubic phase at room temperature. This significant improvement on phase stability can be attributed to the effective encapsulation of NWs by AAM and large specific area of these NWs. To demonstrate device application of these NWs, photodetectors based on these high density CsPbI NWs were fabricated demonstrating decent performance. Our discovery suggests a novel and practical approach to stabilize the cubic phase of CsPbI material, which will have broad applications for optoelectronics in the visible wavelength range.

Metal halide perovskite has emerged as a promising material for light-emitting diodes. In the past, the performance of devices has been improved mainly by optimizing the active and charge injection layers. However, the large refractive index difference among different materials limits the overall light extraction. Herein, we fabricate efficient methylammonium lead bromide light-emitting diodes on nanophotonic substrates with an optimal device external quantum efficiency of 17.5% which is around twice of the record for the planar device based on this material system. Furthermore, optical modelling shows that a high light extraction efficiency of 73.6% can be achieved as a result of a two-step light extraction process involving nanodome light couplers and nanowire optical antennas on the nanophotonic substrate. These results suggest that utilization of nanophotonic structures can be an effective approach to achieve high performance perovskite light-emitting diodes.

Wearable and portable devices contribute to a rapidly growing emerging market for electronics and can find wide applications for wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. [1][2][3][4][5] Typically, wearable devices with attractive attributes such as flexibility, long cruising time, and operation safety are highly desirable. [6][7][8][9][10][11] Recent advances in fields of power generation devices enable sustainable energy harvesting from the environment, such as solar energy, mechanical vibrations and frictions, biofluid and thermal energy from human body, and converted into electricity without external power sources, which introduces the concept of "self-powered" systems. [12][13][14][15][16][17] To realize continuous operation of the entire self-powered devices without interruption from surrounding conditions variation, such as insufficient solar illumination, fully integrated self-powered systems that consist of energy harvesting/conversion devices (e.g., solar cells, nanogenerators, biofuel cells), energy storage devices as intermediate energy storage units (e.g., rechargeable batteries, supercapacitors) and functional devices (e.g., sensors, transistors, biomedical implants) are highly desirable. [18] Planar supercapacitors with interdigitated electrodes constructed on single substrate emerged as one of the highly competitive energy storage devices to complement/replace batteries, offering merits of high power density, separator-free architectures for device miniaturization, and favorable operational safety without using flammable electrolytes. [19][20][21][22] Especially for integration with energy harvesting devices dealing with highly volatile energy input, particularly in wearable applications, supercapacitors possess an appealing capability to accommodate fast and high charging current fluctuation. [23][24][25][26] Although self-sufficient energy modules (e.g., photovoltaic-batteries, nanogenerator-supercapacitors) and selfpowered sensors (e.g., nanogenerator-sensors, battery-sensors) have been reported previously, [12,23,[26][27][28][29][30][31][32] to our best knowledge, demonstration of a fully integrated self-powered sensor system on flexible substrate implemented via additive printable strategy is rarely achieved, mainly due to the challenges on fabrication procedures compatibility and system integration of different device components.Wearable and portable devices with desirable flexibility, operational safety, and long cruising time, are in urgent demand for applications in wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. Herein, a monolithically integrated self-powered smart sensor system with printed interconnects, printed gas sensor for ethanol and acetone detection, and printable supercapacitors and embedded solar cells as energy sources, is successfully demonstrated in a wearable wristband fashion by utilizing inkjet printing as a proof-of-concept. In such a "wearable wristband", the harvested so...

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Hybrid perovskites have emerged as promising candidates for highly efficient light-emitting diodes in the past few years due to their excellent crystallinity, high color purity, wide-range bandgap tunability, and solution processability. However, the reported device external quantum efficiency has not reached the level on par with that of conventional inorganic and organic light-emitting diodes. Moreover, device stability still needs substantial improvement. In this work, we demonstrate the fabrication of perovskite nanophotonic wire array-based light-emitting diodes with a capillary-effect-assisted template method. Compared with the planar control device, the nanostructured device demonstrates 45% improvement of external quantum efficiency from 11% to 16% owing to substantial enhancement on device light extraction efficiency verified by optical modeling. Intriguingly, it is also discovered that the nanostructured device possesses 3.89 times lifetime compared to the planar control device, due to effective template passivation. The results here have clearly shown that with a proper photonic device structure design, both the device performance and lifetime can be significantly improved.