Metal halide perovskite solar cells (PSCs) have undergone rapid progress. However, unstable performance caused by sensitivity to environmental moisture and high temperature is a major impediment to commercialization of PSCs. In the present work, a low-temperature, glass-glass encapsulation technique using high performance polyisobutylene (PIB) as the moisture barrier is investigated on planar glass/FTO/TiO/FAPbI/PTAA/gold perovskite solar cells. PIB was applied as either an edge seal or blanket layer. Electrical connections to the encapsulated PSCs were provided by either the FTO or Au layers. Results of a "calcium test" demonstrated that a PIB edge-seal effectively prevents moisture ingress. A shelf life test was performed and the PIB-sealed PSC was stable for at least 200 days. Damp heat and thermal cycling tests, in compliance with IEC61215:2016, were used to evaluate different encapsulation methods. Current-voltage measurements were performed regularly under simulated AM1.5G sunlight to monitor changes in PCE. The best results we have achieved to date maintained the initial efficiency after 540 h of damp heat testing and 200 thermal cycles. To the best of the authors' knowledge, these are among the best damp heat and thermal cycle test results for perovskite solar cells published to date. Given the modest performance of the cells (8% averaged from forward and reverse scans) especially with the more challenging FAPbI perovskite material tested in this work, it is envisaged that better stability results can be further achieved when higher performance perovskite solar cells are encapsulated using the PIB packaging techniques developed in this work. We propose that heat rather than moisture was the main cause of our PSC degradation. Furthermore, we propose that preventing the escape of volatile decomposition products from the perovskite solar cell materials is the key for stability. PIB encapsulation is a very promising packaging solution for perovskite solar cells, given its demonstrated effectiveness, ease of application, low application temperature, and low cost.

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Loosening tests of bolted joints are carried out under various preloads and excitation amplitudes. Three coatings are utilized to treat bolts, and their effects on the anti-loosening performance are studied. For the MoS 2 coated bolt, a reasonable preload is calculated, and its anti-loosening performance is also examined. It is found that the anti-loosening performance of MoS 2 coating on bolt is better than that of the other two coatings. Under the same equivalent stress as that of the uncoated bolt at the thread root, both the preload and the anti-loosening performance of the MoS 2 coated bolt are significantly greater. Additionally, a FE model is created to simulate the bolted joint, and very good agreement is found between numerical and experimental results.

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Variations in the wind direction over time mean that it is essential to improve the directional adaptability of wind energy harvesters (WEHs) based on wind-induced vibration (WIV) to expand their application potential. Several multi-directional WIV WEHs have been reported in the literature but most of them are not omnidirectional. In particular, no mathematical model has been proposed for omnidirectional WIV WEHs to date. In this Letter, an in-plane omnidirectional piezoelectric WEH with a cylindrical shell, acting as a bluff body and supported by internal piezoelectric composite beams, is proposed. It is deduced that the omnidirectionality of wind energy harvesting can be enhanced by improving the isotropies of the aerodynamic force, stiffness, and electromechanical conversion. For a WEH with three semicircular-shaped supporting beams, a mathematical model suitable for arbitrary wind directions in the horizontal plane was derived. Simulations show that the WEH's stiffness and electromechanical conversion are approximately isotropic. Simulations and experiments demonstrate that the wind direction's effect on the total power is small. The ratio of the experimental minimum to maximum total power is 0.88 at 9 m/s, verifying that the device is an in-plane omnidirectional harvester. An omnidirectionality index including contributions from all directions is proposed with the value of 0.86 at 9 m/s for the prototype. The proposed device configuration and design method may serve as a reference for the development of omnidirectional WIV WEHs.