Efficient and ultra-stable perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) have emerged as a strong contender for next-generation display and information technologies. However, similar to perovskite solar cells, the poor operational stability remains the main obstacle toward commercial applications. Here we demonstrate ultra-stable and efficient PeLEDs with extraordinary operational lifetimes (T50) of 1.0x10^4 h, 2.8x10^4 h, 5.4x10^5 h, and 1.9x10^6 h at initial radiance (or current densities) of 3.7 W/sr/m2 (~5 mA/cm2), 2.1 W/sr/m2 (~3.2 mA/cm2), 0.42 W/sr/m2 (~1.1 mA/cm2), and 0.21 W/sr/m2 (~0.7 mA/cm2) respectively, and external quantum efficiencies of up to 22.8%. Key to this breakthrough is the introduction of a dipolar molecular stabilizer, which serves two critical roles simultaneously. First, it prevents the detrimental transformation and decomposition of the alpha-phase FAPbI3 perovskite, by inhibiting the formation of lead and iodide intermediates. Secondly, hysteresis-free device operation and microscopic luminescence imaging experiments reveal substantially suppressed ion migration in the emissive perovskite. The record-long PeLED lifespans are encouraging, as they now satisfy the stability requirement for commercial organic LEDs (OLEDs). These results remove the critical concern that halide perovskite devices may be intrinsically unstable, paving the path toward industrial applications.Comment: This is a preprint of the paper prior to peer review. New and updated results may be available in the final version from the publishe

Elevation of the Yields of Very Long Chain Polyunsaturated Fatty Acids via Minimal Codon Optimization of Two Key Biosynthetic Enzymes

Eicosapentaenoic acid (EPA, 20:5Δ5,8,11,14,17) and Docosahexaenoic acid (DHA, 22:6Δ4,7,10,13,16,19) are nutritionally beneficial to human health. Transgenic production of EPA and DHA in oilseed crops by transferring genes originating from lower eukaryotes, such as microalgae and fungi, has been attempted in recent years. However, the low yield of EPA and DHA produced in these transgenic crops is a major hurdle for the commercialization of these transgenics. Many factors can negatively affect transgene expression, leading to a low level of converted fatty acid products. Among these the codon bias between the transgene donor and the host crop is one of the major contributing factors. Therefore, we carried out codon optimization of a fatty acid delta-6 desaturase gene PinD6 from the fungus Phytophthora infestans, and a delta-9 elongase gene, IgASE1 from the microalga Isochrysis galbana for expression in Saccharomyces cerevisiae and Arabidopsis respectively. These are the two key genes encoding enzymes for driving the first catalytic steps in the Δ6 desaturation/ Δ6 elongation and the Δ9 elongation/Δ8 desaturation pathways for EPA/DHA biosynthesis. Hence expression levels of these two genes are important in determining the final yield of EPA/DHA. Via PCR-based mutagenesis we optimized the least preferred codons within the first 16 codons at their N-termini, as well as the most biased CGC codons (coding for arginine) within the entire sequences of both genes. An expression study showed that transgenic Arabidopsis plants harbouring the codon-optimized IgASE1 contained 64% more elongated fatty acid products than plants expressing the native IgASE1 sequence, whilst Saccharomyces cerevisiae expressing the codon optimized PinD6 yielded 20 times more desaturated products than yeast expressing wild-type (WT) PinD6. Thus the codon optimization strategy we developed here offers a simple, effective and low-cost alternative to whole gene synthesis for high expression of foreign genes in yeast and Arabidopsis

Returning to Memory An Exhibition of Oracle Bone Script

Oracle bone script was the earliest form of Chinese characters carved on turtle plastrons and animal bones using a sharp tool. Oracle bone script was used for divination through fire in the Shang dynasty (c.1600-1046 BCE). This research explores ways to promote and enhance audience interest in the script through storytelling strategies that use interactive technology in an exhibition context. Through the course of this study, I found that there is a lack of publicity and cultural engagement with oracle bone script and that this has contributed to the general public knowing little about its historical importance. Therefore, I have created a proposal for an exhibition that showcases, through various means, this significant Chinese historical legacy

Water Activity and Solubility Measurements and Pitzer Model Simulation of the MgCl2-RbCl-H2O Ternary System at 298.15 K

Water activities for the MgCl2-RbCl-H2O ternary system and its sub-binary MgCl2-H2O and RbCl-H2O systems at 298.15 K have been measured using the isopiestic method. The measured results for the binary systems agree well with literature data. The measured equal water activity lines for the MgCl2-RbCl-H2O ternary system deviate from Zdanovskii&#39;s rule. The solubilities for the MgCl2-RbCl-H2O ternary system also have been measured using a isothermal visual first/last crystal method, and the results are consistent with one reported set of solubility data. Pitzer&#39;s model was selected to correlate the measured water activity and solubility data and the parameters reported in the literature are re-examined by comparing the model-calculated equal water activity lines and solubilities with experimental values measured in this work. New and reasonable parameters are obtained by fitting the water activity and solubility data measured in this work and those reported in the literature. The water activities and solubilities were simulated with the new parameters and the results show that the Pitzer model can successfully represent the thermodynamic properties and be used to calculate the solubility isotherms.</p

Water Activity and Solubility Measurements and Model Simulation of the CsCI-MgCl2-H2O Ternary System at 323.15 K

Water activities in the ternary system CsCl-MgCl2-H2O and its sub-binary systems at 323.15 K were elaborately measured by an isopiestic method. Moreover, the solubility of the CsCl-MgCl2-H2O system at 323.15 K was also measured by the flow-cloud-point method. A Pitzer model was used to predict the measured water activity and solubility data. The binary parameters for the CsCl-H2O system at 323.15 K were obtained by fitting the measured water activities for this binary system. The calculated water activity and solubility isotherms for the CsCI-MgCl2-H2O system at 323.15 K, with binary parameters only, deviated from the experimental values. This means that it is insufficient with binary parameters only to predict the water activity and calculate the solubility isotherms of the CsCl MgCl2-H2O system at 323.15 K The calculated solubility isotherms with both binary and mixing parameters, obtained by fitting the measured water activity, also deviated from experimental values. A new set of reasonable ternary parameters for the CsCl-MgCl2-H2O system was obtained by fitting the measured water activity and solubility data of this work. The calculated solubility isotherms with these parameters agreed with experimental results