Recent advances in Pb-Sn mixed perovskite solar cells

Organic-inorganic hybrid lead-tin perovskite solar cells(Pb-Sn PSCs)have attracted much attention because of their advantages of low toxicity,variable bandgap,and feasibility for all-perovskite tandem solar cells,and the current power conversion efficiency(PCE)has exceeded 23%.However,due to the rambunctious crystallization process,easily oxidized Sn(Ⅱ)and inadequate energy level arrangement,there are many defects in perovskite films resulting in serious carrier recombination,which makes PCE still lag Pb-based PSCs.The quality of perovskite films is an important factor affecting the overall device performance.The selection and optimization of transport layers not only determines the interface energy level arrangement but also affects the carrier transport.In this paper,the research progress in improving performance of Pb-Sn PSCs in recent years is reviewed from aspects of perovskite layer and transport layers.The profound understanding of different promotion methods is summarized as well.These results have certain guiding significance for the future development and commercial application of Pb-Sn PSCs.

A mixed-cation lead iodide MA_(1-x)EA_xPbI_3 absorber for perovskite solar cells

The mixed-cation lead halide perovskites have emerged as a new class of promising light harvesting materials for solar cells. The formamidinium（FA）, methylammonium（MA） and Cs cations are widely studied in the field of mixed-cation perovskites. Here, we have investigated ethylammonium（EA） as an alternative cation to fabricate a mixed-cation perovskite of MA_（1-x）EA_xPbI_3. We have characterized the materials using the X-ray diffraction（XRD）, scanning electron microscope（SEM）, and UV–vis spectrum. Our results have confirmed the successful incorporation of EA cations into MAPbI_3. Interestingly, the optimal amount of EA to achieve the best performance is quite low. This is different from the FA–MA mixed-cation perovskites although EA and FA have similar radii. In short, the EA–MA mixed-cation perovskite has some material and device properties highly distinguishable from the FA–MA one.

Efficiency of adenoviral vector mediated CTLA4Ig gene delivery into mesenchymal stem cells

Objective To prevent Graft-versus-host disease (GVHD) in rat model, we evaluated the feasibility of mesenchymal stem cells (MSCs) as a gene transfer target and studied the efficiency of recombinant adenovirus mediated gene therapy.Methods We constructed the recombinant adenovirus containing CTLA4lg gene. Rat MSCs of passages 3-5 were infected by the adenovirus, and the transfection efficiency was monitored by GFP markers. We performed flow cytometric analysis, immunohistochemical and Western blotting analysis to identify the CTLA4lg expression. The gene transferred MSCs were tested for their ability to inhibit the allogeneic lymphocyte response in vitro and to prevent GVHD in a rat model.Results Recombinant adenovirus pAd-CTLA4lg was correctly constructed and confirmed. After MSCs were infected by the adenovirus, the CTLA4lg protein was detected not only in transgenic MSCs, but also in the culture medium. In a mixed lymphocytes response (MLR) test, the transgenic MSCs could significantly inhibit the allogeneic lymphocyte response compared with the control groups (P < 0. 05) . A model of GVHD was developed by transplanting bone marrow cells and spleen lymphocytes of F344 rats to lethally irradiated SD rats. The onset of GVHD could be ameliorated or prevented by co-administration of transgenic MSCs. All the rats in the control groups suffered severe acute GVHD. CTLA4lg expression was observed in the liver, intestine, kidney and spleen 30 days post- transplantation.Conclusions Our results indicate that adenoviral vectors could efficiently transfer CTLA4lg gene into MSCs and sustain long-term stable expression in vitro and in vivo.

Collective migrations in an epithelial-cancerous cell monolayer

Collective cell migration is extensively observed in embryo development and cancer invasion.During these processes,the interactions between cells with distinct identities and fates are of importance for boundary formation and host defense against cancer.In this paper,we explore the collective dynamics of a two-dimensional cell mixing monolayer consisting of non-tumorigenic mammary epithelial cells and breast cancer cells.We show that the epithelial-cancerous cell mixing system displays unique sorting behaviors.The epithelial cells aggregate to form scattered clusters,which perform random motion with simultaneous translation and rotation,strikingly distinct from the classical persistent random walk of individual migratory cells.The motility of cancer cells is markedly promoted by the epithelial clusters,exhibiting remarkable contact enhancement of locomotion.A discrete model based on the Johnson-Kendall-Roberts contact mechanics is proposed to identify the influence of intercellular interactions,active migration forces and cell-substrate friction forces on the collective cell dynamics.These findings could advance our understanding of many biological processes,such as cancer metastasis and tissue morphogenesis.

Mediating Mesenchymal Stem Cells Responses and Osteopontin Adsorption via Oligo(ethylene glycol)-amino Mixed Self-assembled Monolayers

Oligo（ethylene glycol） （-OEG） and amino （-NH2） mixed self-assembled monolayers （SAMs） were employed as model substrates to investigate the effect of charge density on the fate of mesenchymal stem cells （MSCs） and osteopontin （OPN） adsorption. We found that all surfaces presenting -NH2 groups favored cell responses regardless of the surface charge. Meanwhile, OPN adsorption could remain stable on the mixed SAMs over a certain range of charge densities. Our work provides some insights into cell responses and protein adsorption to surface charge.

Development of minimum tie line length method for determination of minimum miscible pressure in gas injection process

Gas injection process is a very important technology in enhanced oil recovery.Minimum miscible pressure is one of the key parameters in gas injection processes.Various experimental methods such as slim tube are used to measure MMP.These methods are costly and time consuming.Recently computational methods are used in order to achieve a cost-effective and reliable technique to evaluate MMP.In this work,a new methodology has been proposed for determination of MMP using the minimum tie line length method.A real mixing cell model was developed to estimate the MMP,MME and key tie lines.This method is simple,robust,and faster than conventional one-dimensional simulation of slim tube.The new mixing cells method can accurately determine the whole key tie lines to a shift,regardless of the number of injection gas and reservoir fluid components.Unlike other methods of mixing cells,this method automatically corrects dispersion by additional contacts to achieve the low variation domain of tie line slope.Also,the determination and implementation of the minimum miscibility enrichment are investigated.