Room-Temperature Processing of Inorganic Perovskite Films to Enable Flexible Solar Cells

Inorganic lead halide perovskite materials have attracted great attention recently due to their potential for greater thermal stability compared to hybrid organic perovskites. However, the high processing temperature to convert from the non-perovskite phase to cubic perovskite phase in many of these systems has limited their application in flexible optoelectronic devices. Here, we report a room temperature processed inorganic PSC based on CsPbI2Br as the light harvesting layer. By combing this composition with key precursor solvents, we show that the inorganic perovskite film can be prepared by the vacuum-assist method under room temperature conditions in air. Unencapsulated devices achieved the power conversion efficiency up to 8.67% when measured under 1-sun irradiation. Exploiting this room temperature process, flexible inorganic PSCs based on an inorganic metal halide perovskite material is demonstrated.Comment: 23 pages, 4 figures, and supplemental informatio

Vision, challenges and opportunities for a Plant Cell Atlas

With growing populations and pressing environmental problems, future economies will be increasingly plant-based. Now is the time to reimagine plant science as a critical component of fundamental science, agriculture, environmental stewardship, energy, technology and healthcare. This effort requires a conceptual and technological framework to identify and map all cell types, and to comprehensively annotate the localization and organization of molecules at cellular and tissue levels. This framework, called the Plant Cell Atlas (PCA), will be critical for understanding and engineering plant development, physiology and environmental responses. A workshop was convened to discuss the purpose and utility of such an initiative, resulting in a roadmap that acknowledges the current knowledge gaps and technical challenges, and underscores how the PCA initiative can help to overcome them.</jats:p

Cell-Size Control in Chlamydomonas reinhardtii

In this thesis, I studied the cell-size control in Chlamydomonas and contributed to the below two projects. First, preliminary results show that cdkg1 mutants reduce cell division and show large-cell phenotype. CDKG1 interacts with cyclinD3, and phosphorylates MAT3/RB. CDKG1 concentration peaks at S/M, and scales with mother cell size. CDKG1 concentration per nucleus decreases as cells divide. My data show that CDKG1 mis-expression has a small-cell phenotype that may be due to the inability of cells to eliminate the protein at the end of S/M phase. By measuring the N/C ratio during cell division I ruled out the dilution model for CDKG1 elimination and was able to show that CDKG1 must be actively degraded with each round of cell division. We were able to conclude that CDKG1 functions as a titratable regulator that couples cell size to cell-cycle progression. Second, with an in vivo nuclei marker ble-GFP, I measured N/C in wild-type, cell-size mutants, and vegetative diploids of Chlamydomonas. I concluded that N/C is constant over most of the cell-size range. In combination with previous data from a different eukaryotic phylum, yeast, my data suggest that a constant N/C may be a conserved property of eukaryotic cells. I also found evidence for a lower limit of the nuclear size, which might be a pure physical constraint of the nuclear DNA

Cell Size Control Mechanisms in the Multiple Fission Cell Cycle of Chlamydomonas

Size homeostasis is achieved by a balance between cell growth and cell division, but the underlying mechanisms are yet fully understood. Green alga Chlamydomonas reinhardtii (Chlamydomonas) is a unique model for size control. Instead of the canonical binary fission cell cycle, Chlamydomonas uses a multiple fission cell cycle where a prolonged G1 phase is followed by rapid alternative n rounds of S/M (DNA synthesis and mitosis) cycles to produce 2n daughter cells. Two size checkpoints show size-dependence: the Commitment checkpoint governs a minimum size for a cell to divide at least once, and the S/M checkpoint governs the division number to ensure uniformly sized new-born daughters. A conserved retinoblastoma (RB) tumor suppressor is known to be the master regulator for cell cycle progression in animal cells and higher plants. Previous studies support the idea that the RB pathway in Chlamydomonas regulates the S/M checkpoint. I established microscopy-based mathematic models to explain the mitotic behaviors in the multiple fission cell cycle of Chlamydomonas and characterized additional sizer proteins functioning in the Chlamydomonas RB pathway. I related the molecular mechanisms for size control in yeast, higher plants, and animal early embryogenesis, and further concluded that size sensing in eukaryotes can be explained by general titration mechanisms where cell cycle inhibitors titrate against DNA(/genome) to govern the cell cycle progression

Understanding the impact of C60 at the interface of perovskite solar cells via drift-diffusion modeling

Perovskite solar cells have recently seen rapid improvements in performance with certified efficiencies of above 23%. Fullerene compounds are a very popular electron-transfer material in these devices. In a previous report, it has been shown that while an ultrathin fullerene layer of just 1 nm is sufficient to achieve good device performance, removal of this layer causes a drastic decrease in performance. We provide an explanation to these observed effects by use of a numerical device model. This work provides theoretical support to the experimental understanding of the dominant role of fullerenes in perovskite solar cells

Countermeasure Analysis on Promoting Drinking Water Safety in Shanshan County, Xinjiang Autonomous Region, China

In recent years, China has paid an increasing amount of attention to improving urban and rural drinking water safety, an important aspect of building a healthy and stable society. This study analyzed countermeasures to promote drinking water safety in Turpan City of Shanshan County, in the Xinjiang Autonomous Region. First, we considered the current state of drinking water safety in Shanshan, including issues such as pollution, outdated water treatment technologies, leakage in the water supply pipe network, insufficient emergency management capability in urban areas, and low water supply guarantee rates in rural areas due to poor construction standards. Second, the quantity of guaranteed water resources was estimated; on this basis, an ideal distribution of regional water plants and water supply network needs for the optimal allocation of water resources is suggested. Third, a water purification program was developed to solve untreated water quality problems, including centralized and decentralized water quality treatments alongside intelligent water flow control processes. Water resource conservation and risk control measures are also proposed in order to promote the security of drinking water; equipment updates, and the establishment of an intelligent water management platform are also suggested

Compact Layer Free Perovskite Solar Cells with 13.5% Efficiency

The recent breakthrough of organometal halide perovskites as the light harvesting layer in photovoltaic devices has led to power conversion efficiencies of over 16%. To date, most perovskite solar cells have adopted a structure in which the perovskite light absorber is placed between carrier-selective electron- and hole-transport layers (ETLs and HTLs). Here we report a new type of compact layer free bilayer perovskite solar cell and conclusively demonstrate that the ETL is not a prerequisite for obtaining excellent device efficiencies. We obtained power conversion efficiencies of up to 11.6% and 13.5% when using poly­(3-hexylthiophene) and 2,2′,7,7′-tetrakis­(<i>N</i>,<i>N</i>-di­(4-methoxyphenyl)­amino)-9,9′-spirobifluorene, respectively, as the hole-transport material. This performance is very comparable to that obtained with the use of a ZnO ETL. Impedance spectroscopy suggests that while eliminating the ZnO leads to an increase in contact resistance, this is offset by a substantial decrease in surface recombination

Recent developments in chemical vapor deposition of 2D magnetic transition metal chalcogenides

In recent years, two-dimensional (2D) magnetic transition metal chalcogenides (TMCs) have attracted tremendous research interests thanks to their intriguing properties that are essential in developing future electronic and spintronic devices in this modernizing era. This review aims to introduce recent developments in the preparation of 2D magnetic TMCs, especially chromium and iron-based chalcogenides, their structures, as well as the related intriguing magnetic phenomena. First, the common crystal structures of magnetic TMCs including both layered and nonlayered structures are introduced. Various chemical vapor deposition strategies for synthesizing 2D magnetic TMCs are then introduced with emphasis on the key synthesis parameters. Moreover, the intriguing physical properties associated with 2D TMCs such as magnetic anisotropy, thickness, and phase-dependent magnetic response as well as stability are summarized. Last but not least, challenges and future research directions are briefly discussed in light of recent advances in the field.Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionZ.L. acknowledges support from National Research Foundation Singapore Programme Grants NRF-CRP22-2019-0007, NRF-CRP21-2018-0007, and NRF-CRP22-2019-0004. This research is also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme “Geometrical Quantum Materials” (Grant MOE2018-T3-1-002), and AcRF Tier 1 Grant RG161/19

Parametric Study on the Aerodynamic Characteristics of Wind Guide Barriers for a Train–Bridge System

This paper presents a new type of wind guide barrier (WGB). Through wind tunnel experiments, the key parameters of three types of WGB were studied, as well as their effects on the aerodynamic characteristics of a high-speed train and blunt body box girder system, while the bridge deck wind field was investigated. The results show that the shielding effect is the main factor affecting the windproof performance of the WGB. When the WGB is installed, the mean wind pressure distribution on the train is comparable to that of using a vertical wind barrier while reducing barrier resistance and the resistance of the bridge–barrier system. At the same time, the WGB can guide the oncoming flow, resulting in an increase in the streamwise and vertical wind velocity ratios on the bridge deck, as well as an increase in the maximum aerodynamic coefficient on the train

Cracking behaviors and mechanism of pre-cracked rock specimens under coupled THM fields with chemical processes

In deep rock engineering, natural cracks in rock mass subjected to thermo-hydro-mechanical-chemical (THMC) loads have tendency to initiate and propagate, and result in potential safety hazards. Current literature on cracking behaviors and mechanism of pre-cracked rock under multi-field loads is focused on single (M), two (TM, HM) or three fields (THM, HMC), less on THMC fields. In this study, a series of self-designed triaxial compressive tests were performed to study different THMC fields influencing on mechanical behaviors and failure patterns of pre-cracked red sandstone specimens. A new THMC fracture criterion, recently proposed by our group team, is used to further analyze the crack initiation mechanism of red sandstone under THMC loads. Research results suggest that the stress-strain curve is greatly influenced by the temperature, confining pressure and acidity and alkalinity of chemical solution, but relatively less by the hydraulic pressure. As the temperature and hydraulic pressure increase, the confining pressure decreases, and the acidity or the alkalinity of chemical solutions becomes strong, both the elastic modulus, crack initiation stress and peak strength of specimen are decreased, and the failure pattern is changed from shear failure to tensile failure. The crack initiation stress and peak strength usually have the largest, middle, smallest values in the shear, tension-shear and tensile failures, respectively, while the peak strain has largest value in the mixed tensile-shear failure. The acid solution has greater weakening effect than the alkaline solution with the same concentration. Theoretical results indicate that the temperature and chemical fields influencing on crack initiation is mainly attributable to its weakening of rock fracture toughness, while seepage and stress fields on crack initiation to its change of the stress state at crack-tips. The THMC mechanism of crack initiation can be well revealed by the new THMC fracture criterion