Because of their unique and excellent photophysical properties, lead halide perovskites are widely used in photoelectronic devices such as photodetectors, light-emitting diodes, solar cells, and lasers. Recently it was found that lead halide perovskites also exhibit excellent nonlinear optical properties in nonlinear optics (NLO), including saturated absorption, two-or multiphoton absorption, and nonlinear refraction. It is believed that perovskites will be serious nonlinear optical materials in the future. The nonlinear optical devices prepared from perovskites on the basis of their optical nonlinearity may open up a new viewpoint for the application of information and communication technology. Here the research on lead halide perovskites in NLO is reviewed. The mechanism of nonlinear optical phenomena of lead halide perovskites is analyzed, and some possible methods to improve the optical nonlinearity are summarized. Their applications in passive Q-switched lasers, upconversion lasers, optical limiting, and infrared detection are introduced. Several future research directions and challenges of lead halide perovskites in nonlinear optics are proposed.

The triboelectric nanogenerator (TENG) is an emerging technology that offers excellent potential for the conversion of mechanical energy from rain into electricity for hybrid energy applications. However, a high‐performance TENG is yet to be achieved because a quantitative analysis method for the energy conversion process is still lacking. Herein, a quantitative analysis method, termed the "kinetic energy calculation and current integration" (KECCI) method, which significantly improves the understanding of the mechanical‐to‐electrical energy conversion process, is presented. Based on the KECCI method, a high‐performance TENG is developed by systematically optimizing a biomimetic surface structure and instant switch design, with 1.25 mA short‐circuit current (Isc), 150 V open‐circuit voltage (Voc), and a high energy‐conversion efficiency of 24.89%. Furthermore, a multilayered TENG device is proposed for continuously harvesting the kinetic energy of raindrops for further improvement in the energy‐conversion efficiency. Finally, the multilayered TENGs are integrated with organic photovoltaics, achieving all‐weather energy harvesting. This work presents a validated theoretical basis that will guide further development of TENGs toward higher performances, which will promote the commercialization of hybrid TENG systems for all‐weather applications.

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The emergence of the Internet of Things (IoT) has subverted people’s lives, causing the rapid development of sensor technologies. However, traditional sensor energy sources, like batteries, suffer from the pollution problem and the limited lifetime for powering widely implemented electronics or sensors. Therefore, it is essential to obtain self-powered sensors integrated with renewable energy harvesters. The triboelectric nanogenerator (TENG), which can convert the surrounding mechanical energy into electrical energy based on the surface triboelectrification effect, was born of this background. This paper systematically introduces the working principle of the TENG-based self-powered sensor, including the triboelectrification effect, Maxwell’s displacement current, and quantitative analysis method. Meanwhile, this paper also reviews the recent application of TENG in different fields and summarizes the future development and current problems of TENG. We believe that there will be a rise of TENG-based self-powered sensors in the future.

Through virtualization and resource integration, cloud computing has expanded its service area and offers a better user experience than the traditional platforms, along with its business operation model bringing huge economic and social benefits. However, a large amount of evidence shows that cloud computing is facing with serious security and trust crisis, and building a trust-enabled transaction environment has become its key factor. The traditional cloud trust model usually adopts a centralized architecture, which causes large management overhead, network congestion and even single point of failure. Furthermore, due to a lack of transparency and traceability, trust evaluation results cannot be fully recognized by all participants. Blockchain is a new and promising decentralized framework and distributed computing paradigm. Its unique features in operating rules and traceability of records ensure the integrity, undeniability and security of the transaction data. Therefore, blockchain is very suitable for constructing a distributed and decentralized trust architecture. This paper carries out a comprehensive survey on blockchain-based trust approaches in cloud computing systems. Based on a novel cloud-edge trust management framework and a double-blockchain structure based cloud transaction model, it identifies the open challenges and gives directions for future research in this field.

With the development of the technological age, environmental problems have become more and more acute, and the use of electronic devices in harsh environments has gradually attracted attention, but the...

A thermal diode that rectifies heat current is one of the basic devices for functional heat control. Frequency response is an important feature of many electric devices, such as diodes and transistors. Frequency response measures the ability of a device to process high-frequency signals. In this paper, we systematically study the frequency response of a thermal diode model that consists of two dissimilar Frenkel-Kontorova (FK) segments. The rectification ability of this thermal diode is badly affected when the input temperatures oscillate with a frequency that exceeds a critical value. The dependence of this critical frequency on various system parameters, including system size, interface coupling strength, etc., is quantitatively calculated.