meantime, the ease of the solution process at low temperature renders this technology up-and-coming for large-scale low-cost manufacture. However, these solution-processed perovskite films are usually polycrystalline, which readily form defects at the grain boundaries and on the surface of the films. [1][2][3][4][5][6] Such defects are the center of non-radiative recombination of photo-generated electrons and holes, which causes shorter carrier lifetime and lower open-circuit voltage (V OC ). Hence, in real devices, higher recombination rate occurs close to the interface of the sequentially deposited layers. For typical n-i-p perovskite solar cells (PSCs), the perovskite/hole transport layer (HTL) interface holds the high defect density, such as cation/anion vacancy and dangling bonds, etc., [7,8] resulting in defect-assisted recombination. Additionally, the energy level mis-alignment near the interface due to quasi-fermi level pinning will increase recombination velocity [9] and the recombination loss occurs inevitably across interfaces between holes in HTL and minority carriers (electron) in the perovskite, or HTL themselves. [10,11] These existing recombination loss channels at the surface/ interface of the perovskite will severely limit the V OC and overall efficiency of PSCs.Many studies have demonstrated that passivation is an efficient method to lessen the non-radiative recombination loss at the surface/interface of the perovskite in n-i-p PSCs. For example, excess PbI 2 [4,[12][13][14] was believed to passivate the grain boundaries and interface of electron transport layer with perovskite; conjugated polymers [15] and insulating poly(methyl methacrylate) [16,17] were also used to passivate the interface of perovskite/HTL. Recently, various ammonium halide compounds, [8,18,19] especially bulky organic ammonium halide salts were adopted to passivate the surface of perovskite, such as 1,8-octanediammonium iodide, [3] adamantylammonium hydroiodide, [7] (fluorine-)phenylethylammonium iodide (F-)PEAI, [20][21][22][23] n-hexyl trimethyl ammonium bromide, [24] etc. They could interact with the undercoordinated ions or form low-dimensional perovskite phases to passivate the surface/ interface of bulk perovskite. The stability of devices was also usually improved due to the suppression of ionic migration by the packed organic moiety or the formation of hydrophobic low-dimensional perovskites. [7,23,25] A very recent work by Jiang et al. found exceptionally that the insulating PEAI salt, rather than the 2D layered PEA 2 PbI 4 perovskite, served as a moreThe presence of non-radiative recombination at the perovskite surface/ interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1-naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post-treatment primarily leaves NMAI sal...
lengths, low exciton binding energy, and ease of solution processability, which promise the perovskite-based photovoltaic devices both high efficiency and low manufacture cost. The intense effort to improve power conversion efficiencies (PCEs) has resulted in PCEs of perovskite solar cells (PSCs) increasing from 3.8% in 2009 [5] to over 23% in 9 years. [6,7] Changes in material composition (e.g., using mixed cations and halides together into a 3D lead−halide perovskites, such as [FA/MA]Pb[I/Br] 3 , [8] [FA/Cs]Pb[I/Br] 3 , [9,10] or [Cs/FA/MA]Pb[I/Br] 3[11] ) have played essential role to improve the performances and structural stability. However, the intrinsic instability of the 3D lead−halide perovskites with regard to moisture, heat, light, and oxygen remains to be entirely circumvented. [12,13] Two main measures have been taken to increase the stability of PSCs: providing sufficient protection to the perovskite material [14] and increasing the intrinsic stability of the perovskite material. [15] More importantly, techniques that can improve device stability without sacrificing the efficiency are critical for the future of PSCs. In this regard, strategies called multidimensional perovskite (MDP) using Ruddlesden-Popper type perovskite (Class I) or low dimensional polymorphs passivated 3D perovskites (Class II) were brought into being increasing the intrinsic stability of the perovskite material. [16] Ruddlesden-Popper phase layered perovskites ((RNH 3 ) 2 (MA) n−1 Pb n X 3n+1 , n = 1, 2, 3, 4, 5, …) [17][18][19][20][21] which was introduced by Smith et al. showed albeit low PCE the superior ambient stability, [18] where RNH 3 are large aliphatic or aromatic ammonium cations represented by n-butylammonium (BA) and 2-phenylethylammonium (PEA). (BA) 2 (MA) 2 Pb 3 I 10 as a light absorber retained its performance after exposure to a highhumidity environment for 60 d. [20] So far the highest reported PCE of Ruddlesden-Popper type perovskite-based solar cell is 15.42%. [22] Very recently, Zhang et al. utilized synchrotron source based in situ measurement to disclose the phase transition kinetics during the crystallization of Ruddlesden-Popper type perovskite. This study provided insight into the relationship between phase purity, quantum well orientation, and photovoltaic performance. [23] On the other hand, the approaches that involve low dimensional polymorphs passivated 3D perovskites, or 3D-2D perovskite stacked structures attracted extensive interest in recent years. This approach features not only the Supported by the density functional theory (DFT) calculations, for the first time, a fluorinated aromatic cation, 2-(4-fluorophenyl)ethyl ammonium iodide (FPEAI), is introduced to grow in situ a low dimensional perovskite layer atop 3D perovskite film with excess PbI 2 . The resulted (p-FC 6 H 4 C 2 H 4 NH 3 ) 2 [PbI 4 ] perovskite functions as a protective capping layer to protect the 3D perovskite from moisture. In the meantime, the thin layer facilitates charge transfer at the interfaces, thereby reducing the...
The notoriously poor stability of organic–inorganic hybrid perovskite solar cells is a crucial issue restricting the commercial application of such burgeoning technology. Passivation of bulk perovskite absorber by fluorinated aromatic ammonium salt via low‐dimensional perovskites has been proved to be an effective way of improving stability and efficiency. Herein, the influence of fluorination position (ortho‐, meso‐, and para‐) on the aromatic moiety is studied in terms of their dipole moments and the ability to reduce defect density, extend carrier lifetimes, and assist charge transfer. In addition to the improved power conversion efficiency (PCE) from 19.17% to above 20%, the device treated with 2‐(o‐fluorophenyl)ethylamine iodide exhibits a remarkable open‐circuit voltage (VOC) of 1.21 V. While the 2‐(p‐fluorophenyl)ethylamine iodide‐treated device shows only 1% loss of its initial value under ambient atmosphere (with RH of 10–30%) without encapsulation for 1440 h storage. The molecular structure of fluorinated aromatic cations plays multiple roles in passivating the interface of the perovskite device.
Background: Sarcopenia, particularly low handgrip strength has been observed and correlated in association with hypertension among the older people. However, the results reported in different studies were inconsistent. In the current study, we conducted a systematic review and meta-analysis to reveal the significant association between sarcopenia, handgrip strength, and hypertension in older adults. Methods: PubMed, MEDLINE, Cochrane Library, and EMBASE databases were searched from inception to 15 November 2019 to retrieve the original research studies that addressed the association between sarcopenia, handgrip strength, and hypertension. All the relevant data were retrieved, analyzed, and summarized. Results: Twelve articles met the inclusion criteria and a total of 21,301 participants were included in the metaanalysis. Eight eligible studies have reported the odd ratios (ORs) of hypertension and sarcopenia, and the ORs ranged from 0.41 to 4.38. When pooled the ORs together, the summarized OR was 1.29 [95% confidence interval (CI) =1.00-1.67]. The summarized OR for the Asian group 1.50 (95% CI = 1.35-1.67) was significantly higher than that of Caucasian group 1.08 (95% CI = 0.39-2.97). Eleven studies have provided the data on association between handgrip strength and hypertension. The overall OR and 95% CI was 0.99 (95% CI = 0.80-1.23), showing no significant association. Conclusion: Sarcopenia was associated with hypertension, but no correlation was found between handgrip strength and hypertension in older adults.
Recently, the compositional engineering of lead-free halide double perovskite materials (A2B+B3+X6) has attracted increasing research interests in terms of potential optoelectronic applications. Herein, antimony ions (Sb3+) are introduced to manipulate...
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