Metal halide perovskites are an emerging class of solution processable materials that have exhibited remarkable optoelectronic properties, such as high carrier mobility 1 , long diffusion length 2,3 , bandgap tunability 4,5 , high luminescence efficiency 6 and narrow emission bandwidth 7 . These properties, along with the ease of preparation of halide perovskite materials, have led to great advances in applications such as solar cells [8][9][10][11] , photodetectors 12,13 and light-emitting diodes (LEDs) [14][15][16][17] . The development of perovskite LEDs (PeLEDs) has, in particular, been rapid: in 2014 we reported electroluminescence (EL) from halide perovskites 14 and by 2018 we and others had achieved external quantum efficiencies of >20% 18-21 .

Recently, several light-stimulated artificial synaptic devices have been proposed to mimic photonic synaptic plasticity for neuromorphic computing. Here, the photoelectric synaptic plasticity based on 2D lead-free perovskite ((PEA) 2 SnI 4 ) is demonstrated. The devices show a photocurrent activation in response to a light stimulus in a neuron-like way and exhibit several essential synaptic functions such as short-term plasticity (STP) and long-term plasticity (LTP) as well as their transmission based on spike frequency control. The strength of synaptic connectivity can be effectively modulated by the duration, irradiance, and wavelength of light spikes. The ternary structure of (PEA) 2 SnI 4 causes it to possess varied photoelectric properties by composition control, which enhances the complexity and freedoms required by neuromorphic computing. The physical mechanisms of the memory effect are attributed to two distinct lifetimes of photogenerated carrier trapping/detrapping processes modulated by controlling the proportion of Sn vacancies. This work demonstrates the great potential of (PEA) 2 SnI 4 as a platform to develop future multifunctional artificial neuromorphic systems.

Perovskite nanoplatelets (NPls) hold promise for light-emitting applications, having achieved photoluminescence quantum efficiencies approaching unity in the blue wavelength range, where other metal-halide perovskites have typically been ineffective. However, the external quantum efficiencies (EQEs) of blue-emitting NPl light-emitting diodes (LEDs) have reached only 0.12%. In this work, we show that NPl LEDs are primarily limited by a poor electronic interface between the emitter and hole injector. We show that the NPls have remarkably deep ionization potentials (≥6.5 eV), leading to large barriers for hole injection, as well as substantial nonradiative decay at the NPl/hole-injector interface. We find that an effective way to reduce these nonradiative losses is by using poly(triarylamine) interlayers, which lead to an increase in the  EQE of the blue (464 nm emission wavelength) and sky-blue (489 nm emission wavelength) LEDs to 0.3% and 0.55%, respectively. Our work also identifies the key challenges for further efficiency increases.

Owing to their ease of fabrication, low cost, and high flexibility, organic materials have attracted great interests in photodetector (PD) applications. However, suffering from large dark current, small photocurrent, low on–off ratio, and low sensitivity, performances of bare organic‐based PDs are not satisfactory. Integrating organic materials with other novel semiconductor materials offers an opportunity to overcome these drawbacks. Here, a lateral hybrid organic/lead sulfide (PbS) quantum dot bilayer PD is designed and fabricated, which significantly suppresses the dark current and enhances the photocurrent, leading to improved light detecting capability. Meanwhile, the bilayer PD can be made on a flexible polyimide substrate.

E-textiles are gaining growing popularity recently due to low cost, light weight, and conformable compatibility with clothes in wearable and portable smart electronics. Here, an easy-handing, low cost, and scalable fabricating strategy is reported to fabricate conductive, highly flexible, and mechanically stretchable/twisted fiber gas sensor with great wearability and knittability. The proposed gas sensor is built using commercially available cotton/elastic threads as flexible/stretchable templates and reduced graphene oxide/mesoporous zinc oxide nanosheets as sensing layers to form conducting fibers. The as-prepared fiber demonstrates sensitive sensing response, excellent long-term stability (84 days), low theoretical detection limit (43.5 ppb NO2), great mechanical deformation tolerance (3000 bending cycles, 1000 twisting cycles and 65% strain strength), and washing durability in room-temperature gas detection. More significantly, scalable wearable characteristics including repairability, reliability, stability, and practicability have been efficiently improved, which are achieved by knotting the fractured fibers, incorporating multiple sensors in series/parallel and weaving multisensor array networks integrated into clothes. The good sensing properties, superior flexibility, and scalable applications of wearable fibers may provide a broad window for widespread monitoring of numerous human activities in personal mobile electronics and human–machine interactions.