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Recently, the combination of two-dimensional (2D) materials and perovskites has gained increasing attention in optoelectronic applications owing to their excellent optical and electrical characteristics. Here, we report a self-driven photodetector consisting of a monolayer graphene sheet and a centimeter-sized CH3NH3PbBr3 single crystal, which was prepared using an optimized wet transfer method. The photodetector exhibits a short response time of 2/30 μs by virtue of its high-quality interface, which greatly enhances electron–hole pair separation in the heterostructure under illumination. In addition, a responsivity of ~0.9 mA/W and a detectivity over 1010 Jones are attained at zero bias. This work inspires new methods for preparing large-scale high-quality perovskite/2D material heterostructures, and provides a new direction for the future enhancement of perovskite optoelectronics. [ABSTRACT FROM AUTHOR]

Self‐powered photodetectors (SPDs) are regarded as a new type of photodetectors without external energy sources, exhibiting great potential in the next generation of image sensing, biological detection, and robotics. Here, single crystal CH(NH2)2PbBr3 (FAPbBr3) perovskite with a low trap density of 1.64 × 109 cm−3 is directly integrated onto single crystal germanium (Ge). The band structure of the heterojunction belongs to type‐II alignment type, which is beneficial to the achievement of high responsivity. Therefore, the fabricated Au/FAPbBr3/Ge/Au detector exhibits a high responsivity of 0.33 A W−1, detectivity up to 3.83 × 1011 Jones and relatively fast decay time of 4.94 ms without external bias under 520 nm laser illumination. In addition, a prototype of an imaging system is set up utilizing the photodetector as a sensing pixel, from which the imaging function is verified. This work demonstrates a facile strategy for designing high‐performance SPDs. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate a drain voltage modulated reconfigurable optoelectronic device. It can switch work modes in unipolar response and bipolar response for photodetection mode and neuromorphic photo preprocessing, respectively. The device is fabricated based on perovskite-decorated photogate structure with an indium gallium zinc oxide (IGZO) channel, in which the channel photo-generated carrier concentration can be tuned by applied drain voltage. Under low drain voltage, the photodetection mode is achieved, exhibiting a high responsivity up to $4\times 10$ 2 $\text{A}\cdot \text{W}$ −1. While under high drain voltage, a bipolar response behavior is achieved, in which the low-intensity light induces a negative photo response (NPR) and the high-intensity light leads to a positive photo response (PPR). Furthermore, after contrast-enhanced preprocessing of bipolar devices, the recognition accuracy is enhanced from 89.4% to 92.8% and the efficiency is also improved. This work may contribute to the development of reconfigurable optoelectronic devices and neuromorphic photo preprocessing. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites have exhibited unprecedented advantages for x-ray photon detection due to their exotic properties. Their high-crystalline quality has a great impact for high-detection sensitivity under a low electric field, especially related to the synthesis method. In this work, we analyze the capability of CH3NH3PbI3 (MAPbI3) perovskites as an x-ray detection material and propose to control the temperature gradient (TG) during the synthesis of MAPbI3 single crystal perovskites for device fabrication. Our results show that the decreasing TG can effectively reduce the trap density and improve the crystal quality, which could lead to a boosted sensitivity of 1471.7 μC/Gyair/cm2 under a low electric field of 3.3 V/mm. In addition, a higher detection sensitivity can be achieved by increasing the electric field. Our work presents a strategy to construct high-performance direct x-ray detectors. [ABSTRACT FROM AUTHOR]

The sensitive detection of low-dose X-ray radiation is essential to many X-ray applications. In this article, the ultrasensitive X-ray detector based on pure Cs2AgBiBr6 all-inorganic lead-free perovskite film is successfully demonstrated and encapsulated using a metal casing with a Be window. The high-quality Cs2AgBiBr6 films are obtained through the low-cost solution process with long electron–hole diffusion length (~700 nm) and long carrier lifetime (~750 ns). Benefiting from the excellent properties of the Cs2AgBiBr6 film and the stable ambient provided by the packaging module, the resulting device exhibits attractive X-ray detection capabilities with a minimum detectable dose rate of 145.2 nGyairs−1 and a detection sensitivity up to 1.8 × 104μ nGyair−1 cm−2, which is about a thousand times higher than the sensitivity achieved with commercial a-Se X-ray detectors. Besides, the encapsulated device maintains superior detection performance after 2 months of storage, indicating the favorable reliability of the encapsulated device. This article demonstrates a possibility to use Cs2AgBiBr6 perovskite film and Be window for the sensitive X-ray detection, which will inspire further development of radiation electronics by utilizing all-inorganic lead-free perovskite. [ABSTRACT FROM AUTHOR]

Organolead halide perovskites provide tremendous opportunities for ideal radiation detection due to their high atomic numbers, large carrier mobilities, and long lifetimes. Here, we synthesized high-quality single crystal CH3NH3PbBr3 with a high mobility-lifetime product of $\text {4.1} \times \text {10}^{\text {-2}}$ cm2/V by the developed inverse low temperature crystallization method. The sensitive X-ray detector was fabricated by depositing 50 nm of gold on both sides of the perovskite crystal. This device exhibited a high sensitivity up to $259.9~\mu \text{C}$ /Gy $_{\text {air}}$ /cm2 under the 39 keV X-ray exposure at a small electric field of ~0.83 V/mm and yielded a low noise of $\text {3.1} \times \text {10}^{-\text {23}}\,\,\text{A}^{\text {2}}$ /Hz. Additionally, the sensitivity can be further improved by increasing operating voltage. Our results provided a solution for constructing high-performance X-ray detectors. [ABSTRACT FROM AUTHOR]

In recent years, flexible micro-pressure sensors have been used widely in wearable health monitoring applications due to their excellent flexibility, stretchability, non-invasiveness, comfort wearing and real-time detection. According to the working mechanism of the flexible micro-pressure sensor, it can be classified as piezoresistive, piezoelectric, capacitive and triboelectric types. Herein, an overview of flexible micro-pressure sensors for wearable health monitoring is presented. The physiological signaling and body motions contain a lot of health status information. Thus, this review focuses on the applications of flexible micro-pressure sensors in these fields. Additionally, the contents of sensing mechanism, sensing materials and performance of flexible micro-pressure sensors are introduced in detail. Finally, we predict the future research directions of the flexible micro-pressure sensors, and discuss the challenges in practical applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report an artificial eardrum using an acoustic sensor based on two-dimensional MXene (Ti 3 C 2 T x ), which mimics the function of a human eardrum for realizing voice detection and recognition. Using MXene with a large interlayer distance and micropyramid polydimethylsiloxane arrays can enable a two-stage amplification of pressure and acoustic sensing. The MXene artificial eardrum shows an extremely high sensitivity of 62 kPa -1 and a very low detection limit of 0.1 Pa. Notably, benefiting from the ultrasensitive MXene eardrum, the machine-learning algorithm for real-time voice classification can be realized with high accuracy. The 280 voice signals are successfully classified for seven categories, and a high accuracy of 96.4 and 95% can be achieved by the training dataset and the test dataset, respectively. The current results indicate that the MXene artificial intelligent eardrum shows great potential for applications in wearable acoustical health care devices.