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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 adva...

Optical memories are vitally important for the future development of high speed and low cost information technologies. Current optical memory devices still suffer from difficulties such as scaling-down of size, short-life expectancy, and non-volatility without the control of a gate electrode. To resolve these obstacles, a robust photoelectronic memory device is designed and demonstrated based on the integration of amorphous InGaZnO (a-IGZO), GNSs, and nitride multiple-quantum-wells light-emitting diode (MQWs LED). Utilizing the inherent nature of the band alignment between a-IGZO and graphene nanosheets (GNSs), electrons can transfer from a-IGZO to GNSs causing a persistent photoconductivity (PPC). With the long-lasting lifetime of PPC, the signal can be written optically and the encoded signal can be read both electrically and optically. The read and write processes reveal little current degradation for more than 10,000 sec, even repeated for more than hundred times. The device can convert invisible information to visible signal, and the encoded information can be simply erased under a reversed bias without a gate electrode. In addition, the memory device possesses a simple vertically stacked structure for 3D integration, and it is compatible with established technologies.

With the rapid development of technology, electronic devices have become omnipresent in our daily life as they have brought much convenience in every aspect of human activity. Side-by-side, electronic waste (e-waste) has become a global environmental burden creating an ever-growing ecological problem. The transient device technology in which the devices can physically disappear completely in different environmental conditions has attracted widespread attention in recent years owing to its emerging application potential spanning from biomedical to military use. In this work, we demonstrated the first attempt for a dissolvable ecofriendly flexible photodetector using a hybrid of graphene and chlorophyll on a poly(vinyl alcohol) substrate. The whole device can physically disappear in aqueous solutions in a time span of ∼30 min, while it shows a photoresponsivity of ∼200 A W–1 under ambient conditions. The high carrier mobility of graphene and strong absorption strength of a green photon harvesting layer, chl...

Numerous investigations of photon upconversion in lanthanide-doped upconversion nanoparticles (UCNPs) have led to its application in the fields of bioimaging, biodetection, cancer therapy, displays, and energy conversion. Herein, we demonstrate a new approach toward lanthanide-doped UCNPs and a graphene hybrid planar and rippled structure photodetector. The multi-energy sublevels from the 4fn electronic configuration of lanthanides results in longer excited state lifetime for photogenerated charge carriers. This opens up a new regime for ultra-high-sensitivity and broadband photodetection. Under 808 nm infrared light illumination, the planar hybrid photodetector shows a photoresponsivity of 190 AW–1, which is higher than the currently reported responsivities of the same class of devices. Also, the rippled graphene and UCNPs hybrid photodetector on a poly(dimethylsiloxane) substrate exhibits an excellent stretchability, wearability, and durability with high photoresponsivity. This design makes a significan...

Integrating different dimentional materials on vertically stacked p-n hetero-junctions have facinated a considerable scrunity and can open up excellent feasibility with various functionalities in opto-electronic devices. Here, we demonstrate that vertically stacked p-GaN/SiO2/n-MoS2/Graphene heterostructures enable to exhibit prominent dual opto-electronic characteristics, including efficient photo-detection and light emission, which represents the emergence of a new class of devices. The photoresponsivity was found to achieve as high as ~10.4 AW−1 and the detectivity and external quantum efficiency were estimated to be 1.1 × 1010 Jones and ~30%, respectively. These values are superier than most reported hererojunction devices. In addition, this device exhibits as a self-powered photodetector, showing a high responsivity and fast response speed. Moreover, the device demonstrates the light emission with low turn-on voltage (~1.0 V) which can be realized by electron injection from graphene electrode and holes from GaN film into monolayer MoS2 layer. These results indicate that with a suitable choice of band alignment, the vertical stacking of materials with different dimentionalities could be significant potential for integration of highly efficient heterostructures and open up feasible pathways towards integrated nanoscale multi-functional optoelectronic devices for a variety of applications.

The LEM can read the encoded signal electrically and enable the signal communication via optical detection and provides the capability for parallel reading process, which enables to raise the transmission rate of signal dramatically.

Light-based information processing has the potential to increase speed, security, and scalability of electronic devices if issues in the device complexity could be resolved. We here demonstrate an integrated nanoelectronic device that can combine, store, and manipulate optical and electronic information. Employing a mechanically flexible and multilayered structure, a device is realized that shows memristive behavior. Illumination is shown to control the device operation in several unique ways. First, the device produces photocurrent that allows us to read out the device state in a self-powered manner. More importantly, a varying light intensity modulates the switching transition in a proportional manner that is akin to a neuron with variable plasticity and which can be taught and queried using either light or electrical inputs. This behavior enables a multilevel light-controlled logic and teaching schemes that can be applied to light-based communication devices and provides a route toward ubiquitous and low-cost sensors for future internet of things applications.

Hybrid quantum dot–graphene photodetectors have recently attracted substantial interest because of their remarkable performance and low power consumption. However, the performance of the device greatly depends on the interfacial states and photogenerated screening field. As a consequence, the sensitivity is limited and the response time is relatively slow. In order to circumvent these challenges, herein, a composite graphene and graphene quantum dot (GQD) photodetector on lead zirconate titanate (Pb(Zr0.2Ti0.8)O3) (PZT) substrates has been designed to form an ultrasensitive photodetector over a wide range of illumination power. Under 325 nm UV light illumination, the device shows sensitivity as high as 4.06 × 109 A W−1, which is 120 times higher than reported sensitivity of the same class of devices. Plant derived GQD has a broad range of absorptivity and is an excellent candidate for harvesting photons generating electron–hole pairs. Intrinsic electric field from PZT substrate separates photogenerated electron–hole pairs as well as provides the built-in electric field that causes the holes to transfer to the underlying graphene channel. The composite structure of graphene and GQD on PZT substrate therefore produces a simple, stable, and highly sensitive photodetector over a wide range of power with short response time, which shows a way to obtain high-performance optoelectronic devices.

Composite materials can play a decisive role to reveal novel physical properties and enable to advance new generation technologies. Here, we discover that phototransistors based on the integration of two-dimensional graphene nanosheets (GNSs) and amorphous indium–gallium–zinc–oxide (a-IGZO) semiconductors exhibit a giant photo-to-dark current ratio and long-lasting persistent photoconductivity (PPC). Under the illumination of UV light (350 nm) at 50 mW/cm2, a photo-to-dark current ratio up to 2.0 × 107 was obtained, which is about 3 orders of magnitude higher than its pure a-IGZO device counterpart. Moreover, the GNSs/a-IGZO phototransistor possesses an enduring lifetime up to years for the recovery of the transfer characteristics after switching off the UV light. The giant and long-lasting PPC leads GNSs/a-IGZO to become an excellent conductor with conductivity much better than indium tin oxide. The observed unique features represent a semiconductor–conductor transition. In addition to next generation fl...

Graphene quantum dots (GQDs) have been prepared for the first time using raw plant leaf extracts of Neem (Azadirachta indica) and Fenugreek (Trigonella foenum-graecum) by a facile, hydrothermal method at 300 °C for 8 hours in water, without the need of any passivizing, reducing agents or organic solvents. High resolution transmission electron microscope studies showed that the average sizes of the GQDs from Neem (N-GQDs) and Fenugreek (F-GQDs) were 5 and 7 nm respectively. N-GQDs and F-GQDs exhibit high quantum yields of 41.2% and 38.9% respectively. Moreover, the GQDs were utilized to prepare a white light converting cap based on the red-green-blue (RGB) color mixing method.

The LEM can read the encoded signal electrically and enable the signal communication via optical detection and provides the capability for parallel reading process, which enables to raise the transmission rate of signal dramatically.

The integration of a light-emitting transistor based on graphene/insulator/semiconductor with downconversion emitters enables the manipulation of emitted light covering the whole chromaticity space, including white-light emission. This novel arbitrary-color light emitter offers a promising approach for new applications in optoelectronic devices ranging from displays to solid-state lighting.

Metal-organic frameworks (MOFs) have recently emerged as attractive materials for their tunable properties, which have been utilized for diverse applications including sensors, gas storage, and drug delivery. However, the high porosity and poor electrical conductivity of MOFs restrict their optoelectronic applications. Owing to the inherent tunability, a broadband photon absorbing MOF can be designed. Combining the superior properties of the MOFs along with ultrahigh carrier mobility of graphene, for the first time, this study reports a highly sensitive, broadband, and wearable photodetector on a polydimethylsiloxane substrate. The external quantum efficiency of the hybrid photodetector is found to be >5 × 108%, which exceeds all the reported values of similar devices. The porosity of the MOF and ripple structure graphene can assist the trapping of photons at the light-harvesting layer. The device photoresponsivity is found to be >106 A W−1 with a response time of

Stretchable devices possess great potential in a wide range of applications, such as biomedical and wearable gadgets and smart skin, which can be integrated with the human body. Because of their excellent flexibility, two-dimensional (2D) materials are expected to play an important role in the fabrication of stretchable devices. However, only a limited number of reports have been devoted to investigating stretchable devices based on 2D materials, and the stretchabilities were restricted in a very small strain. Moreover, there is no report related to the stretchable photodetectors derived from 2D materials. Herein, we demonstrate a highly stretchable and sensitive photodetector based on hybrid graphene and graphene quantum dots (GQDs). A unique rippled structure of poly(dimethylsiloxane) is used to support the graphene layer, which can be stretched under an external strain far beyond published reports. The ripple of the device can overcome the native stretchability limit of graphene and enhance the carrier generation in GQDs due to multiple reflections of photons between the ripples. Our strategy presented here can be extended to many other material systems, including other 2D materials. It therefore paves a key step for the development of stretchable electronics and optical devices.

We develop graphene-based multiple heterojunctions to realize sensors with a very high sensitivity (

The resonant coupling between cadmium-free I-III-VI2 group quantum dots (QDs) and metal nanostructures has been investigated. Via a SiO2-packaging synthetic procedure, the emission intensity of green ZCIS/ZnS QDs can be greatly enhanced by three times through the localized surface plasmon of Au nanoparticles. Moreover, the bandwidth of the emission spectrum can be narrowed by 17 nm, and the resultant quantum yield is more than 50% which sets up the highest reported value up today for green I-III-VI2 QDs. Our strategy for the improved characteristics of emission spectrum may open a facile alternative for the development of cadmium-free QD light emitting diodes and other optoelectronic devices.