Visible blind near-infrared (NIR) photodetection is essential when it comes to weapons used by military personnel, narrow band detectors used in space navigation systems, medicine, and research studies. The technological field of filterless visible blind, NIR omnidirectional photodetection and wearability is at a preliminary stage. Here, we present a filterless and lightweight design for a visible blind and wearable NIR photodetector capable of harvesting light omnidirectionally. The filterless NIR photodetector comprises the integration of distinct features of lanthanide-doped upconversion nanoparticles (UCNPs), graphene, and micropyramidal poly(dimethylsiloxane) (PDMS) film. The lanthanide-doped UCNPs are designed such that the maximum narrow band detection of NIR is easily accomplished by the photodetector even in the presence of visible light sources. Especially, the 4f electronic configuration of lanthanide dopant ions provides for a multilevel hierarchical energy system that provides for longer lifetime of the excited states for photogenerated charge carriers to transfer to the graphene layer. The graphene layer can serve as an outstanding conduction path for photogenerated charge carrier transfer from UCNPs, and the flexible micropyramidal PDMS substrate provides an excellent platform for omnidirectional NIR light detection. Owing to these advantages, a photoresponsivity of ∼800 AW is achieved by the NIR photodetector, which is higher than the values ever reported by UCNPs-based photodetectors. In addition, the photodetector is stretchable, durable, and transparent, making it suitable for next-generation wearable optoelectronic devices.

The emergence of self-healing devices in recent years has drawn a great amount of attention in both academics and industry. Self-healed devices can autonomically restore a rupture as unexpected destruction occurs, which can efficiently prolong the life span of the devices; hence, they have an enhanced durability and decreased replacement cost. As a result, integration of wearable devices with self-healed electronics has become an indispensable issue in smart wearable devices. In this study, we present the first self-powered, self-healed, and wearable ultraviolet (UV) photodetector based on the integration of agarose/poly­(vinyl alcohol) (PVA) double network (DN) hydrogels, which have the advantages of good mechanical strength, self-healing ability, and tolerability of multiple types of damage. With the integration of a DN hydrogel substrate, the photodetector enables 90% of the initial efficiency to be restored after five healing cycles, and each rapid healing time is suppressed to only 10 s. The proposed device has several merits, including having an all spray coating, self-sustainability, biocompatibility, good sensitivity, mechanical flexibility, and an outstanding healing ability, which are all essential to build smart electronic systems. The unprecedented self-healed photodetector expands the future scope of electronic skin design, and it also offers a new platform for the development of next-generation wearable electronics.

The development of optical memory with attractive features such as long-lasting, nonvolatile, high-speed, and low-energy consumption is vitally important in the information age. Owing to these advantages, optical memory has been popular for more 10 years. Recently, flexibility has become desirable for the application of wearable devices and smart artificial intelligence; for conventional optical memory, this is still difficult to achieve. To combine optical memory with soft materials, this study presents a flexible and photoelectronic switchable multilevel memory device with long-lasting nonvolatile properties. On the basis of the integration of nanoscale (graphene nanoflakes) and macroscale graphene heterojunctions, a device achieves switchable memory states up to 196 distinct levels under the illumination of lasers with different wavelengths. The photoelectronic memory device can be written optically and erased by both optical and electric methods. Additionally, the device possesses several unique features including a low working bias of 0.5 V, nonvolatility for over 10 000 s, and mechanical stability for more than 10 000 bending cycles. Notably, in previous studies, polymers with poor mobility were used as a conducting channel, which can greatly limit the amplitude of the light-induced switching ratio and electrical performance. In stark contrast, in our device, the graphene layer with the mobility exceeding several orders of magnitude was used to serve as a conducting channel, enabling one to overcome the existing shortcoming. Our approach therefore not only provides an alternative paradigm for the development of photoelectronic memory but also holds great promise for practical applications due to its compatibility with current technologies.

Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is so-called "green gap". In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs points the way towards a promising avenue of solid-state lighting.

Owing to the need for dynamic, real‐time, and on‐site data collection in internet of things applications, the realization of ultra‐sensitive sensing networks with self‐powered, flexible, and lightweight devices has become an important issue for the development of sensor systems. In this work, a novel, high‐performance, self‐powered photodetector is achieved through the combination of photogating, piezo‐phototronic, and ferroelectric effect by incorporating a ferroelectric thin film of poly(vinylidene fluoride‐co‐trifluoroethylene) in a rationally designed device structure with suitable band alignment, which can modulate carrier transport behavior at the interface due to the internal electric field produced by light illumination, external strain, or voltage‐poled dipole. This enables photocurrent and overall device performance to improve significantly. The unprecedented photodetector presented in this study has several merits, including mechanical flexibility and light weight that allow it to adapt to arbitrary surface topology; additionally, its self‐powering capability and high reliability are urgently needed for the demanding functionality of devices for the development of next‐generation optoelectronic devices, spanning from wearable communication to unattended harsh environments with a human‐friendly interface.