Black orthorhombic (B-γ) CsSnI3 with low toxicity and excellent optoelectronic properties is a promising candidate for perovskite solar cell (PSC). However, the performance of the B-γ CsSnI3-based PSCs is much lower than their lead-based or organotin-based counterparts due to the heavy self-doping of Sn2+ to form Sn4+ under ambient-air conditions. Here, this undesirable oxidation in CsSnI3 is restricted by engineering the localized electron density with phthalimide (PTM) additive. The lone electron pairs of NH and two CO units of PTM are designed to form trigeminal coordination bonding with Sn2+, resulting in reduced defect density and relatively grain-ordered perovskite film. The champion efficiencies of 10.1% and 9.6% are obtained for the modified rigid and flexible B-γ CsSnI3-based PSCs, respectively. These encapsulated devices maintain 94.3%, 83.4%, and 81.3% of their initial efficiencies under inert (60 days), ambient (45 days), and 1 Sun continuous illumination at ∼70 °C (2000 min) conditions, respectively.

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Tri-cation and dual-anion mixed perovskites have been widely utilized in perovskite solar cell (PSC) applications due to their novel properties such as high absorption, high stability, and low cost. To commercialize the PSCs, further improving the device performance without detrimentally changing the device configuration is important at present. Herein, Au@SiO 2 nanoparticles (NPs) are introduced to modify the interface between mesoporous TiO 2 (mp-TiO 2 ) and mixed perovskite with increased main photovoltaic parameters of the device, resulting in a ≈29% enhancement of power conversion efficiency (PCE) from 15.8% to 20.3%. The origins of the enhancement have been studied by exploring the optical absorption, optical power distribution, and charge carrier behaviors within the system. The small perturbation transient photovoltage measurement exhibits prolonged charge carrier lifetimes after the Au@SiO 2 NPs incorporation, and time of flight photoconductivity measurement shows that charge carrier mobilities of this system are also enhanced. These characteristics make metallic nanostructures a promising functional material in facile tuning of the charge carriers transport and further boosting the PCE of the PSCs.

Emerging development of flexible acoustic devices focuses on constructing large-area acoustic sensing networks with high spatial and temporal resolution, enabling the applications in acoustic sensing and positioning, particularly in underwater and medical fields. Here a piezoelectric fiber-like device is fabricated by thermal drawing technique to deliver acoustic sensing functionalities at fiber-optic length scales, flexibility and uniformity. The resulting piezoelectric fiber device operates in the frequency range of 2-8 MHz with signal-to-noise ratio above 20 dB. Additionally, a single piezoelectric fiber can simultaneously demodulate two monochromatic sound signals with the frequency gap from 0.01 MHz to 30 MHz. As a proof-of-concept, a two-dimensional 3×3 fiber array is fabricated to detect and position an underwater acoustic source with the spatial resolution of centimeter.

materials, piezoelectric materials, which can convert mechanical shape changes into electric outputs, are particularly favorable to fabricate wearable devices for mechanicalrelated sensing and power generation. [15][16][17] According to material molecular compositions, piezoelectric materials are generally divided into ceramics and polymers. Indeed, even though inorganic piezoelectric materials offer high piezoelectric property, they are mechanically hard and brittle, which have difficulties to be directly applied to wearable devices. Besides, many piezoelectric ceramics contain heavy metal elements such as lead, that are harmful to human and environment. [18][19][20] On the other hand, piezoelectric polymers, represented by polyvinylidene fluoride (PVDF) and its copolymer poly[(vinylidenefluoride-cotrifluoroethylene] (P(VDF-TrFE)), are more preferable for wearable devices as they are lightweight, stretchable, environmentfriendly and chemically stable. [21,22] To construct piezoelectric polymer fibers, electrospinning, as a representative template-free method, [23,24] is a versatile technique to produce extended length of fiber-shaped structures with a number of advantages such as large surface area, tunable surface morphologies, and enhanced mechanical performance. [25][26][27][28] With electrospinning, when the droplet of polymer solution is charged by high applied voltage, the liquid droplet is pulled into a thin fiber and then collected by the grounded electrode. However, this liquid-to-solid transferring process normally results in randomly distributed fibers with poor electrical properties and limited response to mechanical stimuli. Therefore, to improve the performance of electrospun fibers, several methods have been demonstrated to obtain aligned electrospun fibers. [29][30][31][32][33] Two most frequently adopted methods are: 1) using a high-speed rotating collector with a very sharp edge, [34][35][36] and 2) using two separated parallel electrodes. [37,38] A very high rotating speed (>3000 rpm) is necessary for the rotating collector method, which brings high requirements to the fabrication facilities and increases electricity consumption. Also, the necessary role of sharp edge further restricts the amount of highly aligned electrospun fibers that can be collected. The parallel electrode method, on the other hand, can only fabricate aligned electrospun fibers in a very limited length, typically on millimeter scale.Advances in functional fabrics enable the realization of wearable devices in the form factor of fibers that can be seamlessly adapted in our daily lives. For mechanical-related sensing and power generation, piezoelectric materials are particularly favorable because they can convert mechanical shape changes into electric outputs. Electrospinning is a widely applied technique to produce extended length of fiber-shaped piezoelectric devices. However, this versatile process normally results in randomly distributed fibers with poor electrical properties and limited response to mechanical stimuli. H...