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, chlorophyll, result in the photocurrent gain of the device as high as 103 with subsecond response time under the illumination of red light. The newly designed photodetector shown here yields zero waste with a minimum impact on the environment, which is very useful for the development of the sustainability of our planet.

With the superiority of laser-level intensity, narrow spectral line width, and broad-angular emission, random lasers (RLs) have drawn considerable research interests for their potential to carry out a variety of applications. In this work, the applications associated with optical-encoded technologies, including security printing, military friend or foe identification (FFI), and anticounterfeiting of documents are highlighted, and the concept of a transient RL “smart ink” has been proposed. The proof-of-concept was demonstrated as invisible signatures, which encoded the messages through the spectral difference of spontaneous emission and RL under specified conditions. Next, the possibility of encoding the data with multibit signals was further confirmed by exploiting the threshold tunability of RLs. Moreover, the transient characteristic of this smart ink and its capability to be attached on freeform surfaces of different materials were also shown. With the advantages of a facile manufacturing process and multiple purposes, it is expected that this ink can soon be carried out in a variety of practical utilities.

Printing technology has led to a multitude of revolutions in design, conception, fabrication, and application of optoelectronics nowadays especially for wearables and one‐off devices. Recent advances range from solar cells, batteries, sensors, LEDs, displays, biomedical widgets to smart tags. Inkjet‐printed random lasers (IPRLs), demonstrated here, fill in the crucial but missing piece of the puzzle in printed optoelectronics as well as progress in laser research. A broad emission spectrum of IPRL inks covering more than 75% gamut of CIE color space is successfully exploited and well adopted by commercial desktop inkjet printers. Furthermore, based on the digital, ink‐efficient, mask‐free patterning, and drop‐on‐demand printing technique, a series of long‐anticipated proofs‐of‐concept including on‐chip laser lighting modules, red‐yellow‐green‐blue pixel‐based laser displays, and ink‐crypto/laser‐coded security printing technique are also demonstrated.

To surmount the scalability limitations of the nanoelectronics industry, the invention of resistance random access memory (RRAM) has drawn considerable attention in recent years for being a new-era memory. Nevertheless, the data transmission speed of RRAM is confined by virtue of its sequential reading nature. To improve upon this weakness, a hybrid optical/electric memory with I ON/I OFF ratio up to 105 and laser-level optical signal is proposed. The device was engineered through an adroit design of integrating a random laser (RL) into the conducting bridge random access memory (CBRAM). According to the electrochemical metallization (ECM) effect of CBRAM, agglomerative silver nanoparticles form in the insulating layer during the ON/OFF switching process, which can serve as scattering centers. By adding CdSe/ZnS quantum dots (QDs) as the gain medium, a random laser system is obtained. Due to the quantum confinement effect, the device also features spectral tunable signal feedback by modulating the size of the QDs. In this study, devices with two different sizes of QDs are demonstrated such that a multiple-bit AND gate logic can be achieved. The innovation behind this RL-ECM memory might facilitate a key step toward the development of ultrahigh-speed information technology.