Engineering the passivation routes of perovskite films towards high performance solar cells.

Passivation treatment is an effective method to suppress various defects in perovskite solar cells (PSCs), such as cation vacancies, under-coordinated Pb2+ or I-, and Pb-I antisite defects. A thorough understanding of the diversified impacts of different defect passivation methods (DPMs) on the device performance will be beneficial for making wise DPM choices. Herein, we choose a hydrophobic Lewis acid tris(pentafluorophenyl)borane (BCF), which can dissolve in both the perovskite precursor and anti-solvent, as the passivation additive. BCF treatment can immobilize organic cations via forming hydrogen bonds. Three kinds of DPMs based on BCF are applied to modify perovskite films in this work. It is found that the best DPM with BCF dissolved in anti-solvent can not only passivate multiple defects in perovskite, but also inhibit δ phase perovskite and improve the stability of devices. Meanwhile, DPM with BCF dissolved in both the perovskite precursor and anti-solvent can cause cracks and voids in perovskite films and deteriorate device performance, which should be avoided in practical applications. As a result, PSCs based on optimal DPMs of BCF present an increased efficiency of 22.86% with negligible hysteresis as well as improved overall stability. This work indicates that the selection and optimization of DPMs have an equally important influence on the photovoltaic performance of PSCs as the selection of passivation additives.

Double-Sided Bonding Process Enables X-ray Flat Panel Detectors.

Metal halide perovskites have demonstrated superior sensitivity, lower detection limits, stability, and exceptional photoelectric properties in comparison to existing commercially available X-ray detector materials, showing their potential for shaping the next generation of X-ray detectors. Nevertheless, significant challenges persist in the seamless integration of these materials into pixelated array sensors for large-area X-ray direct detection imaging. In this article, we propose a strategy for fabricating large-scale array devices using a double-sided bonding process. The approach involves depositing a wet film on the surface of a thin-film transistor substrate to establish a robust bond between the substrate and δ-CsPbI3 wafer via van der Waals force, thereby facilitating area-array imaging. Additionally, the freestanding polycrystalline δ-CsPbI3 wafer demonstrated a competitive ultralow detection limit of 3.46 nGyair s-1 under 50 kVP X-ray irradiation, and the δ-CsPbI3 wafer still maintains a stable signal output (signal current drift is 3.5 × 10-5 pA cm-1 s-1 V-1) under the accumulated radiation dose of 234.9 mGyair. This strategy provides a novel perspective for the industrial production of large-area X-ray flat panel detectors utilizing perovskites and their derivatives.

Triptolide Reduces Neoplastic Progression in Hepatocellular Carcinoma by Downregulating the Lipid Lipase Signaling Pathway.

Hepatocellular carcinoma (HCC), which is the third leading cause of cancer-related mortality in the world, presents a significant medical challenge. Triptolide (TP) has been identified as an effective therapeutic drug for HCC. However, its precise therapeutic mechanism is still unknown. Understanding the mechanism of action of TP against HCC is crucial for its implementation in the field of HCC treatment. We hypothesize that the anti-HCC actions of TP might be related to its modulation of HCC lipid metabolism given the crucial role that lipid metabolism plays in promoting the progression of HCC. In this work, we first demonstrate that, both in vitro and in vivo, TP significantly reduces lipid accumulation in HCC cells. Additionally, we notice that lipoprotein lipase (LPL) expression is markedly upregulated in HCC, and that its levels are positively connected with the disease's progression. It is interesting to note that TP dramatically reduces LPL activity, which in turn prevents HCC growth and reduces lipid accumulation. Additionally, the effect of TP on LPL is a direct correlation. These results definitely demonstrate that TP protects hepatocytes against abnormal accumulation of lipids by transcriptionally suppressing LPL, which reduces the development of HCC. This newly identified pathway provides insight into the process through which TP exerts its anti-HCC actions.

Regulating buried interface properties and alleviating micro-strain of crystals for efficient perovskite solar cells.

Surface properties of SnO2 and their effects on the growth of perovskite films play a crucial role for perovskite solar cells (PSCs). Herein, a facile strategy to synchronously regulate the buried interface defects and energy level arrangement, as well as improve the crystallinity of perovskite films with alleviated micro-strain by pre-modifying the SnO2 surface with ammonium hexafluorophosphate (NH4PF6) is proposed. The device achieved the promising PCE of 22.50% and improved stability.

Intermediate-Phase-Modified Crystallization for Stable and Efficient CsPbI3 Perovskite Solar Cells.

All-inorganic CsPbI3 perovskite solar cells (PSCs) are becoming desirable for their excellent photovoltaic ability and adjustable crystal structure distortion. However, the unsatisfactory crystallization of the perovskite phase is unavoidable and leads to challenges on the road to the development of high-quality CsPbI3 perovskite films. Here, we reported the intermediate-phase-modified crystallization (IPMC) method, which introduces pyrrolidine hydroiodide (PI) before the formation of the perovskite phase. The hydrogen bonding, which originates from the interaction between the -NH in PI and the dimethylammonium iodide (DMAI) from the precursor solution, improved the crystallization conditions and further prompted the transition from the DMAPbI3 phase to CsPbI3 perovskite phase. The application of the IPMC method not only decreased the trap density but also changed the energy alignment for better separation of electron-hole pairs. As a result, the devices based on the PI-CsPbI3 perovskite films reached an efficiency of 18.72% and maintained 85% of their initial PCE after 1000 h of being stored in an ambient environment (∼25% RH, 25 °C). This work stimulates inspiration on how to conveniently fabricate high-quality perovskite films in industry.

Dual Effect of Superhalogen Ionic Liquids Ensures Efficient Carrier Transport for Highly Efficient and Stable Perovskite Solar Cells.

Defect accumulation and nonradiative recombination at the interface of the electron-transport layer (ETL) and the photosensitive layer are inevitable obstacles to efficient and stable perovskite solar cells (PSCs). Herein, we reported a dual-effect interface modification strategy that employs potassium tetrafluoroborate (KBF4) molecules for the simultaneous passivation of the SnO2/perovskite interface and perovskite grain boundaries. The introduced highly electronegative BF4- enriched at the SnO2 surface and the chemical bond interaction between them can effectively reduce the hydroxyl (-OH) group defects on the surface of SnO2, improve electron mobility, and reduce nonradiative recombination. Meanwhile, partial K+ diffuses into the grain boundaries, causing the halogen ions to be uniformly distributed in the perovskite film and resulting in better crystallinity. Therefore, the performance of the experimental device was improved from 20.34 to 22.90% compared with the reference device, with a high electrical performance (JSC = 25.1 mA cm-2, VOC = 1.137 V). In particular, the unencapsulated target PSCs retained 85% of their original PCE after aging for 1000 h under ambient conditions (70 ± 10% RH) in the dark.

Coral-inferred historical changes of nickel emissions related to industrial and transportation activities in the Beibu Gulf, northern South China Sea.

As one of the most abundant metals in heavy oils, Ni has suffered so notably increasing impacts from industrial and traffic activities that anthropogenic Ni emissions have altered natural geochemical processes. The coral Ni/Ca has become a reliable proxy for characterizing marine pollution, but this potential has been unexploited for highlighting oil pollution. Here, we utilized a high-resolution record of geochemical parameters (Ni/Ca, δ18O, and δ13C) in a Porites coral of an offshore island in the northern South China Sea to reconstruct of Ni distribution patterns in surface seawater from 1984 to 2015. The coral Ni/Ca ratios exhibit minor fluctuations, except for multiple mutation peaks (0.20 ± 0.42 µmol/mol) during the period from 1984 to 1993. The ratio was low and stable (0.10 ± 0.09 µmol/mol) from 1994 to 2008, and then increased rapidly with significant variations (1.60 ± 4.56 µmol/mol) from 2009 to 2015. The coral Ni/Ca ratios captured all significant Ni discharges, and this demonstrates its potential for recording oil spill episodes. The historical variations in the contributions of Ni indicate that industrial and traffic activities should be responsible for changes in the anthropogenic input. The leaks and consumptions of petroleum likely account for the primary Ni emission sources.

A Selective Targeting Anchor Strategy Affords Efficient and Stable Ideal-Bandgap Perovskite Solar Cells.

Mixed lead-tin perovskite solar cells (LTPSCs) with an ideal bandgap are demonstrated as a promising candidate to reach higher power conversion efficiency (PCE) than their Pb-counterparts. Herein, a Br-free mixed lead-tin perovskite material, FA0.8 MA0.2 Pb0.8 Sn0.2 I3 , with a bandgap of 1.33 eV, as a perovskite absorber, is selected. Through density functional theory calculations and optoelectronic techniques, it is demonstrated that both Pb- and Sn-related A-site vacancies are pushed into deeper energetic depth, causing severe nonradiative recombination. Hence, a selective targeting anchor strategy that employs phenethylammonium iodide and ethylenediamine diiodide as co-modifiers to selectively anchor with Pb- and Sn-related active sites and passivate bimetallic traps, respectively, is established. Furthermore, the selectivity of the molecular oriented anchor passivation is demonstrated through energetic depth specificity of Pb- and Sn-related traps. As a result, a substantially enhanced open-circuit voltage (VOC ) from 0.79 to 0.90 V for the LTPSCs is achieved, yielding a champion PCE of 22.51%, which is the highest PCE among the reported ideal-bandgap PSCs. The VOC loss is reduced to 0.43 V.

Boosting Photovoltaic Performance and Stability of Super-Halogen-Substituted Perovskite Solar Cells by Simultaneous Methylammonium Immobilization and Vacancy Compensation.

Perovskite solar cells (PSCs) are susceptible to intrinsic structural instability associated with the presence of inorganic halide anions and organic cation vacancies, thus leading to the deterioration or even premature failure of devices. Herein, we develop an efficient strategy using super-halogen BH4- substitution to simultaneously immobilize methylammonium and substitute iodide vacancy for high-performance PSCs based on the dihydrogen bonding interactions. The introduced super-halogen BH4- groups not only significantly reduce the vacancy density but also effectively inhibit the decomposition of the CH3NH3+ group by forming perovskite CH3NH3PbI3-x(BH4-)x. The power conversion efficiency (PCE) of the assembled mesoporous devices is remarkably promoted from 18.43 to 21.10%, accompanied by significant increase of both Jsc and Voc without obvious hysteresis. The superior PSCs can retain 90 and 80% of their initial PCE even after being stored for 1200 h under environmental conditions (50 ± 10% RH) and 240 h at 85 °C in the dark, respectively. Moreover, it delivers excellent optical stability under ultraviolet illumination. This work provides an avenue to improve both the long-term stability and photovoltaic performance of PSCs.

The Effect of Constituent Ratios and Varisized Ammonium Salts on the Performance of Two-Dimensional Perovskite Materials.

Two-dimensional perovskite solar cells (PSCs) with high moisture resistance are a key topic in the photovoltaic field. However, their lower power conversion efficiencies (PCEs) in comparison to 3 D PSCs is still an urgent problem to be solved. It is vital to understand the impact of constituent ratios and ammonium salt sizes on the photovoltaic performance and humidity stability. Based on the formula of (RNH3 )2 (MA)n-1 Pbn I3n+1 (n=1, 3, 5, 7, 9, and 11), a series of 2 D perovskites is prepared by introducing varisized ammonium salts of ethylammonium iodide (EAI), propylammonium iodide (PAI), and butylammonium iodide (BAI). The effects of the constituent ratios and varisized ammonium salts on the properties of the 2 D perovskites were studied. 2 D perovskite devices based on larger n and smaller ammonium salt size are found to exhibit better performances. However, the moisture resistance of the 2 D perovskite devices is higher when n is smaller and the ammonium salt size is larger. Therefore, the EA2 MA10 Pb11 I34 (n=11) 2 D perovskite device displays the best photovoltaic performance, with the highest PCE of 16.93 %, whereas BA2 MA2 Pb3 I10 (n=3) 2 D perovskite, with the largest contact angle of 79.8°, can retain over 85 % of the initial PCE after 1440 h aging at 50 % relative humidity. This work indicates the PCE and stability of 2 D perovskites can be conveniently and effectively adjusted by controlling the 2 D constituent ratios and ammonium salt sizes, so as to obtain efficient 2 D PSCs with high stability.

Elimination of Yellow Phase: An Effective Method to Achieve High Quality HC(NH2 )2 PbI3 -based Perovskite Films.

Formamidinium lead iodide-based (FAPbI3 ) perovskite is widely used in the field of photovoltaics, owing to its suitable bandgap (ca. 1.45 eV) and better thermal stability. FAPbI3 has two polymorphs (black α-FAPbI3 and yellow δ-FAPbI3 ) at ambient temperature. The yellow δ-FAPbI3 , which has no photoactivity, has a chain-like structure that likely hinders electron transport and reduces photovoltaic performance. However, pure-phase black α-FAPbI3 without any yellow phase is difficult to obtain and the underlying mechanism of the phase transition is rarely investigated. In this study, a facile bi-additive method (BA method) has been developed to completely eliminate the yellow δ-FAPbI3 phase by inducing a phase transition from δ-FAPbI3 to α-FAPbI3 . HI and Pb(SCN)2 were employed as dual additives. Based on the investigation of the annealing time and temperature, we determined that the BA method can induce the phase transition and enhance the stability of α-FAPbI3 . Owing to the enhanced crystallization as well as uniform morphology of the BA film, the perovskite solar cells (PSCs) exhibited an increased power conversion efficiency (PCE). Furthermore, the optimal devices displayed excellent stability and maintained over 80 % of initial PCE after aging for 400 h in air. This work provides a new insight into the fabrication of high-quality pure α-FAPbI3 perovskite films and makes high efficiency photovoltaic devices a reality.

Boosting Photovoltaic Properties and Intrinsic Stability for MA-Based Perovskite Solar Cells by Incorporating 1,1,1-Trimethylhydrazinium Cation.

The most critical reason for limiting the extensive study and promotion of MA-based perovskites is their intrinsic instability when compared to FA-based perovskites. Therefore, it is necessary to develop a simple and effective method to improve their intrinsic stability. Herein, the 1,1,1-trimethylhydrazinium cation (TMH+) was first introduced into MAPbI3 to fabricate high-performance mixed-cation perovskite solar cells (PSCs) with an enhanced power conversion efficiency (PCE) of 19.86%, which benefits by the improved crystallization and morphology of films. On the one hand, the slightly large size of TMH+ is complementary to the low tolerance factor of MAPbI3 and then enhances the structure stability. On the other hand, the presence of methyl groups in TMH+ is beneficial to promote the hydrophobicity of MA-based perovskite. More importantly, the hydrazinium group can effectively inhibit the production of Pb0 in perovskites, which is the initial stage of degradation. As a result, the intrinsic stability of PSCs has been observably boosted. After aging at 45 ± 5% RH for 1800 h and 85 °C for 200 h, the unencapsulated PSCs retained 77 and 79% of initial PCE, respectively. This work provides a new design for the selection of suitable cations with special structures and chemical groups to enhance the moisture resistance and intrinsic stability of MA-based perovskite at the source of degradation.

Coral trace metal of natural and anthropogenic influences in the northern South China Sea.

The composition and concentrations of trace metals in coastal seawater have changed in parallel with variations in geochemical processes, climate and anthropogenic activities. To evaluate the response of trace metals in coastal seawater to climatic changes and human disturbances, we report annual-resolution trace element data for a Porites coral core covering ~100years of continuous growth from a fringing reef in Xiaodonghai Bay in the northern South China Sea. The results suggested that the trace metal contents in the coral skeleton demonstrated decadal to interdecadal fluctuations with several large or small peaks in certain years with remarkable environmental significances. All of the trace metals in coastal surface seawater, especially Cr and Pb (related to industrial or traffic emissions), were impacted by terrestrial inputs, except for Sr and U, which were impacted by the surface seawater temperature (SST). Moreover, Mn, Ni, Fe and Co were also contributed by weapons and military supplies during wars, and Cu, Cd and Zn were further impacted by upwelling associated with their biogeochemical cycles. Ba and rare earth element (REE) in coastal surface seawater were dominated by runoff and groundwater discharge associated with precipitation. This study provided the potential for some trace metals (e.g., REE, Ba, Cu, Cd, and Zn) in coral skeletons to be used as proxies of natural (e.g., upwelling and precipitation) and anthropogenic (e.g., war and coastal construction) variability of seawater chemistry to enable the reconstruction of environmental and climatic changes through time.

Effects of fertilization and clipping on carbon, nitrogen storage, and soil microbial activity in a natural grassland in southern China.

Grassland managements can affect carbon (C) and nitrogen (N) storage in grassland ecosystems with consequent feedbacks to climate change. We investigated the impacts of compound fertilization and clipping on grass biomass, plant and soil (0-20 cm depth) C, N storage, plant and soil C: N ratios, soil microbial activity and diversity, and C, N sequestration rates in grassland in situ in the National Dalaoling Forest Park of China beginning July, 2011. In July, 2012, the fertilization increased total biomass by 30.1%, plant C by 34.5%, plant N by 79.8%, soil C by 18.8% and soil N by 23.8% compared with the control, respectively. Whereas the clipping decreased total biomass, plant C and N, soil C and N by 24.9%, 30.3%, 39.3%, 18.5%, and 19.4%, respectively, when compared to the control. The plant C: N ratio was lower for the fertilization than for the control and the clipping treatments. The soil microbial activity and diversity indices were higher for the fertilization than for the control. The clipping generally exhibited a lower level of soil microbial activity and diversity compared to the control. The principal component analysis indicated that the soil microbial communities of the control, fertilization and clipping treatments formed three distinct groups. The plant C and N sequestration rates of the fertilization were significantly higher than the clipping treatment. Our results suggest that fertilization is an efficient management practice in improving the C and N storage of the grassland ecosystem via increasing the grass biomass and soil microbial activity and diversity.