Chemical Reaction of FA Cations Enables Efficient and Stable Perovskite Solar Cells.

Organometal halide perovskite solar cells (PSCs) have received great attention owing to a rapid increase in power conversion efficiency (PCE) over the last decade. However, the deficit of long-term stability is a major obstacle to the implementation of PSCs in commercialization. The defects in perovskite films are considered as one of the primary causes. To address this issue, isocyanic acid (HNCO) is introduced as an additive into the perovskite film, in which the added molecules form covalent bonds with FA cations via a chemical reaction. This chemical reaction gives rise to an efficient passivation on the perovskite film, resulting in an improved film quality, a suppressed non-radiation recombination, a facilitated carrier transport, and optimization of energy band levels. As a result, the HNCO-based PSCs achieve a high PCE of 24.41% with excellent storage stability both in an inert atmosphere and in air. Different from conventional passivation methods based on coordination effects, this work presents an alternative chemical reaction for defect passivation, which opens an avenue toward defect-mitigated PSCs showing enhanced performance and stability.

In Situ Surface Reconstruction toward Planar Heterojunction for Efficient and Stable FAPbI3 Quantum Dot Solar Cells.

Pure-phase α-FAPbI3 quantum dots (QDs) are the focus of an increasing interest in photovoltaics due to their superior ambient stability, large absorption coefficient, and long charge-carrier lifetime. However, the trap states induced by the ligand-exchange process limit the photovoltaic performances. Here, a simple post treatment using methylamine thiocyanate is developed to reconstruct the FAPbI3 -QD film surface, in which a MAPbI3 capping layer with a thickness of 6.2 nm is formed on the film top. This planar perovskite heterojunction leads to a reduced density of trap-states, a decreased band gap, and a facilitated charge carrier transport. As a result, a record high power conversion efficiency (PCE) of 16.23% with negligible hysteresis is achieved for the FAPbI3 QD solar cell, and it retains over 90% of the initial PCE after being stored in ambient environment for 1000 h.

Co3 Se4 Quantum Dots as an Ultrastable Host Material for Potassium-Ion Intercalation.

Potassium-ion batteries (KIBs) are receiving increased attention due to their cost-effective and similar energy-storage mechanism to lithium-ion batteries. However, the lack of appropriate electrode materials is still hampered for their development, which is mainly caused by the large size of the potassium ions (1.38 Å) including low structural stability and poor electrochemical redox reaction kinetics. Herein, Co3 Se4 quantum dots (QD) encapsulated by N-doped carbon (CSC) are reported as an anode material for KIBs, in which a morphology change process occurs. Benefiting from the unique uniform nanostructure reducing the ion-diffusion length, the improved electronic conductivity, and the enhanced protective effect of N-doped carbon (NC) alleviating volume fluctuation, the CSC demonstrates excellent electrochemical performance. The core-shell-like CSC composite demonstrates remarkable discharge capacity (410 mA h g-1 at 0.1 A g-1 after 550 cycles, 360 mA h g-1 at 0.5 A g-1 after 3200 cycles) and excellent cyclic performance over 10 000 cycles at 1 A g-1 . Density functional theory calculations show a larger reaction energy of Co3 Se4 QD than bulk Co3 Se4 , a lower barrier of K atom migration in Co3 Se4 QD than bulk Co3 Se4 , and also favor the intercalation reaction rather than replacement reaction. In situ X-ray diffraction and ex situ transmission electron microscopy are further used to evaluate potassiation/depotassiation phenomena.

CTLA-4 gene A/G polymorphism associated with diabetes mellitus in Han Chinese.

OBJECTIVE: To investigate the association of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) gene A/G polymorphism with susceptibility to diabetes mellitus in Han Chinese. METHODS: An A/G transition at position 49 of exon 1 was analyzed in 31 patients with type 1 diabetes, 31 patients with type 2 diabetes, and 36 controls were analyzed by polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: A highly significant increase in the frequency of the G allele was seen in patients with type 1 diabetes compared with controls (66.1 % vs. 34.7%, respectively; P < 0.0005; OR = 3.670) . This reflected an increase in the GG genotype in patients (48.4% vs. 22.2%, respectively; P =0.025; OR =3.281) and a significant decrease in the AA genotype (16.1 % vs. 52.8%, respectively; P = 0.002). The allele frequencies of A and G in patients with type 2 diabetes were not significantly different from controls(A/G, 50.0/50.0% vs. 65.3/34.7%; P = not significant) . The distribution of genotype, however, differed significantly. This difference reflected an increase in the AG genotype in patients (54.8% vs.25.0%, respectively; P=0.012; OR=3.643) and a decrease in the AA genotype (22.6% vs. 52.8%, respectively; P=0.011). CONCLUSIONS: CTLA-4 49 AA is protective from diabetes mellitus, whereas, CTLA-4 49 G allele (both as homozygotes and as heterozygotes ) confers an increased risk of diabetes mellitus.