A new class of 2D transition metal carbides, carbonitrides and nitrides, termed MXenes, has emerged as a new candidate for many applications in electronics, optoelectronics, and energy storage. Since their first discovery in 2011, MXenes have gathered increasingly more interest owing to their unique physical, chemical, and mechanical properties that can be tuned by different surface terminations and transition metals. In particular, the intriguing optical and electrical properties, including transparency, saturable absorption, and high conductivity, grant MXenes various roles in photodetectors, such as transparent electrodes, Schottky contacts, photoabsorbers, and plasmonic materials. Given the solution‐processability, MXenes also hold great potential for large‐scale synthesis, and thus are favored for a number of electronic and photonic device applications. In this review, recent advances in photodetectors based on 2D MXenes are summarized. Despite the fact that such applications have only recently been explored compared with other 2D materials, MXenes have shown promise in low‐cost and high‐performance photodetection.

high-performance photodetection is highly desirable in various fields, including optical communication, imaging, and environmental monitoring. [4][5][6] Currently, GaN, Si, InGaAs, and other semiconductors have dominated the ultraviolet to near-infrared photodetection market. [7][8][9][10] These detectors are mostly assembled on rigid substrates and usually require relatively thick active materials for photonic detection, therefore, they are not compatible with flexible systems or suitable for low cost manufacturing.The demand for flexible devices has driven the research in emerging functional materials that are bendable. To date, various functional materials have been explored for constructing flexible photodetectors, such as zero-dimensional (0D) semiconductor nanostructures, 2D layered materials, and perovskites. [11][12][13][14] They can be facilely transferred to arbitrary rigid substrates and directly deposited on flexible substrates, which are favorable for flexible optoelectronics. Particularly, organometal halide perovskites (OHPs) have demon strated intriguing properties, including large absorption coefficients, tunable bandgaps, long carrier diffusion length, and high carrier mobility. [15][16][17][18][19][20] Nevertheless, their organic parts Flexible devices are garnering substantial interest owing to their potential for wearable and portable applications. Here, flexible and self-powered photodetector arrays based on all-inorganic perovskite quantum dots (QDs) are reported. CsBr/KBr-mediated CsPbBr 3 QDs possess improved surface morphology and crystallinity with reduced defect densities, in comparison with the pristine ones. Systematic material characterizations reveal enhanced carrier transport, photoluminescence efficiency, and carrier lifetime of the CsBr/KBr-mediated CsPbBr 3 QDs. Flexible photodetector arrays fabricated with an optimum CsBr/KBr treatment demonstrate a high open-circuit voltage of 1.3 V, responsivity of 10.1 A W −1 , specific detectivity of 9.35 × 10 13 Jones, and on/off ratio up to ≈10 4 . Particularly, such performance is achieved under the self-powered operation mode. Furthermore, outstanding flexibility and electrical stability with negligible degradation after 1600 bending cycles (up to 60°) are demonstrated. More importantly, the flexible detector arrays exhibit uniform photoresponse distribution, which is of much significance for practical imaging systems, and thus promotes the practical deployment of perovskite products.The "Internet of Things" (IoT) has been expected to reshape or even revolutionize human daily lives. As a fundamental technology of the IoT, flexible optoelectronics, such as solar power sources, display panels, and photodetectors, have attracted substantial research interest globally. [1][2][3] Moreover,

We have developed quantitative and spatially resolved imaging techniques to identify the origin of nonradiative-radiative recombination and carrier transport losses in perovskite solar cells, offering potential for future real-time tracking of the lab-scaled devices and fast assessment of screening the large-area modules. By dual-chloride passivation strategy, the resulting 25.49 cm 2 perovskite solar module achieves a certified power conversion efficiency of 17.88%.

emiconductor lasers have typically been used to tackle speed and capacity bottlenecks in data communications 1 . However, due to the relatively high manufacturing costs and the relatively complex driver circuits of lasers 2 , as well as eye safety issues, alternative solutions have been sought for future applications in human-centric systems, short-distance communications and indoor wireless data services. Light-emitting diodes (LEDs) are a cost-effective and low-power alternative 2-4 . LED-based links are, in particular, expected to be extensively used in Internet of Things (IoT) and 6G technologies, and in moderate/high-speed photonic interconnects, visible light communications (VLC), underwater communications and accurate indoor positioning applications [2][3][4][5] .The potential use of LEDs in next-generation data communications is driven by the rapid development of energy-efficient LEDs that can function as illumination and signalling devices. The concepts and fundamental principles of LED links are illustrated in Box 1. Micro-LEDs (µLEDs) based on crystalline inorganic III-V semiconductors have been widely examined for communications 2 . Because of advances in epitaxy, lithography and flip-chip techniques 6 , III-V µLEDs have delivered a modulation bandwidth from several hundred megahertz to over one gigahertz 2,7 . A non-polar m-plane InGaN/GaN µLED with a high modulation bandwidth of 1.5 GHz was demonstrated in 2018 7 , and a 1.3 GHz electrical-to-optical bandwidth quantum dot (QD) µLED was recently reported with a data rate of 4 Gbps (ref. 8 ). Nevertheless, conventional approaches are challenged by the high requirements for low size, weight, power and cost of next-generation data communication systems 5,9,10 .Organic semiconductors, colloidal quantum dots (CQDs) and metal halide perovskites offer tailorable optoelectronic properties, mechanical flexibility and low-cost processing 10 . These characteristics make them attractive candidates for use in low-cost and low-power LED links in next-generation integrated and scalable data communication modules. Thus, while conventional inorganic thin-film technologies are likely to continue to play a dominant role in optical communications 9,11 , we believe that LEDs based on these emerging materials can provide a complementary role. In this Review, we examine the development of emerging semiconductor materials for LEDs and colour converters. We first consider the fundamentals of LED-based optical communication systems, and then explore efforts to boost the frequency response and enhance the external quantum efficiency (EQE) of LEDs based on emerging materials. Finally, we consider the challenges that exist in developing these LEDs for practical communication systems.