All-inorganic CsPbI 3 perovskite is emerging to be an alternative light-harvesting material in solar cells owing to the enhanced stability and comparable photovoltaic performance compared to organic−inorganic hybrid perovskites. However, the desirable black phase α-CsPbI 3 is not stable at room temperature and degrades rapidly to a nonperovskite yellow phase δ-CsPbI 3 . Herein, we introduce a compositional engineering approach via incorporating Bi 3+ in CsPbI 3 to stabilize the α-phase at room temperature. Fully inorganic solar cells based on the Bi-incorporated α-CsPb 1−x Bi x I 3 compounds demonstrate a high PCE of 13.21% at an optimal condition (incorporation of 4 mol % Bi 3+ ) and maintain 68% of the initial PCE for 168 h under ambient conditions without encapsulation. This is the first attempt of partial substitution of the "B"-site of the perovskite to stabilize the α-CsPbI 3 , which paves the way for further developments of such perovskites and other optoelectronic devices.O rganic−inorganic halide perovskite materials have attracted tremendous research interest owing to their intriguing optical characteristics as well as promising application in next-generation optoelectronic devices. 1−6 Among the various hybrid halide perovskites, CH 3 NH 3 PbI 3 (MAPbI 3 ) and HC(NH 2 ) 2 PbI 3 (FAPbI 3 ) have been frequently studied and have achieved power conversion efficiencies (PCEs) exceeding 20% in solar cells. 7−15 However, due to the hygroscopicity and thermally unstable nature of organic cation MA + , MAPbI 3 is thermally unstable and vulnerable to moisture. 16−20 Even for the more thermostable FAPbI 3 , the presence of hygroscopic FA + also makes it suffer from the moisture stability issue. 8,21−23 In order to improve the stability and photovoltaic performance of the devices, a series of Cs-incorporated systems have been developed, 24−34 such as Cs x MA 1−x PbI 3 , 24 Cs x FA 1−x PbI 3 , 27,28,30 FA 0.83 Cs 0.17 Pb-(I 1−x Br x ) 3 , 31 and Cs x (MA 0.17 FA 0.83 ) 1−x Pb(I 0.83 Br 0.17 ) 3 . 29,32 However, these Cs-incorporated systems still face big challenges for the long-term stability due to the remaining organic components.Recently, all-inorganic cesium lead halide perovskites (CsPbX 3 ) are emerging to be alternative light-harvesting materials in solar cells and have exhibited excellent ability to resist moisture and heat. 35−39 Nevertheless, CsPbBr 3 has a very large band gap of 2.3 eV, which is unable to absorb light with long-range wavelengths and usually results in low PCE of the solar cells. 38−40 Compared to CsPbBr 3 , black phase α-CsPbI 3 (Figure 1a) has a more suitable band gap of 1.73 eV for solar

A full numerical solution for the mixed elastohydrodynamic lubrication (EHL) in point contacts is presented in this paper, using a new numerical approach that is simple and robust, capable of handling three-dimensional measured engineering rough surfaces moving at different rolling and sliding velocities. The equation system and the numerical procedure are unified for a full coverage of all the lubrication regions including the full film, mixed and boundary lubrication. In the hydrodynamically lubricated areas the Reynolds equation is used. In the asperity contact areas, where the film thickness is zero, the Reynolds equation is reduced to an expression equivalent to the mathematical description of dry contact problem. In order to save computing time, a multi-level integration method is used to calculate surface deformation. Sample cases under severe condition show that this approach is capable of analyzing different cases in a full range of λ ratio, from infinitely large down to nearly zero (less than 0.03). [S0742-4787(00)00101-6]

Atomic-scale interface engineering in BaTiO3@TO2 nanofibers (TiO2 nano-fibers embedded with BaTiO3 nano-particles) leads to concurrent enhancement of electric displacement and breakdown strength in poly(vinylidene fluoride) (PVDF)-based nanocomposites. An ultrahigh energy density of ≈20 J cm(-3) is achieved with only 3 vol% nanofibers, which is by far the highest discharged energy density of PVDF-based nanocomposites.

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The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

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Heterovalent Bi-doped CsPb1−xBixBr3 perovskites greatly improve the light absorption and photostriction of CsPbBr3 crystals.