Novel C3N4-Assisted Bilateral Interface Engineering for Efficient and Stable Perovskite Solar Cells.

g-C3N4-assisted interface engineering has been developed as an effective method to improve the efficiency and stability of perovskite solar cells (PSCs). However, most of the reported works used g-C3N4-induced single-interface modification, which is difficult to passivate the bilateral interfaces of the perovskite layer at the same time. In this paper, we fabricated two kinds of C3N4 materials simultaneously (w-CN and y-CN) after the twice calcination of melamine and used them in the bilateral interface modification toward all-inorganic PSCs. The two kinds of C3N4 play different roles in different interface engineering. On the front interface, w-CN could optimize band level arrangement and improve the perovskite film quality, which contributes to the efficiency of the device. On the back interface, y-CN could also improve the film quality of the perovskite layer, accelerating the extraction of charge carriers. The champion efficiency of the CsPbIBr2-based device treated by the bilateral interface is significantly enhanced from 7.8 to 10.1%. Moreover, the modified perovskite film exhibits negligible degradation after 40 min of exposure in the ambient environment with a relative humidity of 70%, while the pristine perovskite film has a rapid degradation within 20 min.

Intrinsic Self-Trapped Emission in 0D Lead-Free (C4 H14 N2 )2 In2 Br10 Single Crystal.

Low-dimensional lead halide perovskite materials recently have drawn much attention owing to the intriguing broadband emissions; however, the toxicity of lead will hinder their future development. Now, a lead-free (C4 H14 N2 )2 In2 Br10 single crystal with a unique zero-dimensional (0D) structure constituted by [InBr6 ]3- octahedral and [InBr4 ]- tetrahedral units is described. The single crystal exhibits broadband photoluminescence (PL) that spans almost the whole visible spectrum with a lifetime of 3.2 µs. Computational and experimental studies unveil that an excited-state structural distortion in [InBr6 ]3- octahedral units enables the formation of intrinsic self-trapped excitons (STEs) and thus contributing the broad emission. Furthermore, femtosecond transient absorption (fs-TA) measurement reveals that the ultrafast STEs formation together with an efficient intersystem crossing has made a significant contribution to the long-lived and broad STE-based emission behavior.

A Highly Red-Emissive Lead-Free Indium-Based Perovskite Single Crystal for Sensitive Water Detection.

Low-dimensional luminescent lead halide perovskites have attracted tremendous attention for their fascinating optoelectronic properties, while the toxicity of lead is still considered a drawback. Herein, we report a novel lead-free zero-dimensional (0D) indium-based perovskite (Cs2 InBr5 ⋅H2 O) single crystal that is red-luminescent with a high photoluminescence quantum yield (PLQY) of 33 %. Experimental and computational studies reveal that the strong PL emission might originate from self-trapping excitons (STEs) that result from an excited-state structural deformation. More importantly, the in situ transformation between hydrated Cs2 InBr5 ⋅H2 O and the dehydrated form is accompanied with a switchable dual emission, which enables it to act as a PL water-sensor in humidity detection or the detection of traces of water in organic solvents.

The influence of silver core position on enhanced photon absorption of single nanowire α-Si solar cells.

Photon absorption of single nanowire solar cells can be modulated by metallic core. Silver core was integrated into α-Si single nanowire solar cells (SNSCs), and the influence of silver core position on enhanced photon absorption efficiency and the short circuit current (J(sc)) was investigated. The finite-difference time domain (FDTD) method was used to rigorously solve Maxwell's equations in two dimensions. The J(sc) decreases when the silver core is integrated into the center of nanowire. However, the photon absorption efficiencies and J(sc) could be enhanced by tuning the core position in the nanowire. J(sc) enhancement of 21.4% is achieved when nanowire radius R is 190 nm, core radius r is 30 nm, the silver core is located in the negative Y-axis and the distance from the center of silver core to the origin d is 102 nm under realistic solar illumination.

Ultrasensitive Electrochemiluminescence Immunoassay Based on Signal Amplification of 0D Au-2D WS2 Nano-Hybrid Materials.

In this study, we proposed a novel Ru(bpy)32+-Au-WS2 nanocomposite (Ru-Au-WS2 NCs) nano-hybrid electrochemiluminescence (ECL) probe for the highly sensitive detection of carcinoembryonic antigen (CEA). This system utilizes Au nanoparticles (Au NPs) as a bridge to graft the high-performance of a Ru(bpy)32+ ECL emitter and WS2 nanosheet with excellent electrochemical performance into an ECL platform, which shows outstanding anodic ECL performance and biosensing platform due to the synergetic effect and biocompatibility of Au NPs and WS2 nanosheet. Because the ECL intensity of Ru(bpy)32+ is sensitively affected by the antibody-antigen insulator, a preferable linear dependence was obtained in the concentration range of CEA from 1 pg·mL-1 to 350 ng·mL-1 with high selectivity (LOD of 0.3 pg·mL-1, S/N = 3). Moreover, the ECL platform had good reproducibility and stability and exhibited excellent anti-interference performance in the detection process of CEA. We believe that the platform we have developed can expand the opportunities for the detection of additional high specificity-related antibodies/antigens and demonstrate broad prospects for disease diagnosis and biochemical research.

Inverted Pyramid Morphology Control by Acid Modification and Application for PERC Solar Cells.

Silicon inverted pyramid (IP) structures, with lower reflectance and increased surface recombination, are one of the best choices for light-trapping structures of high-efficiency silicon solar cells. The solution process of IP generally goes through three main steps: porous silicon etched by metal-assisted chemical etching, acid etching, and alkali anisotropic etching. In this paper, the role that acid modification plays in IP preparation and the application of our optimized texture for passivated emitter and rear solar cells (PERC) were investigated. Experimental results show that acid plays a decisive role in optimizing and modifying the morphology of porous silicon; thus, the morphology of porous silicon has no direct influence on the morphology of IP. In addition, the opening size of IP is mainly determined by the size of silicon micron holes modified by the acid process. PC1D simulation results manifest that IPs can increase the short-circuit current density (J sc) of devices by 1.04 mA/cm2 and power conversion efficiency by 0.55%; hence, our optimized IP-based PERC achieve the highest simulative conversion efficiency of 23.21%. This is an effective and important way to manipulate the structure of IP, which points out the direction of fabrication and application of high-efficiency IP textures.

High-Efficiency Silicon Inverted Pyramid-Based Passivated Emitter and Rear Cells.

Surface texturing is one of the most important techniques for improving the performance of photovoltaic (PV) device. As an appealing front texture, inverted pyramid (IP) has attracted lots of research interests due to its superior antireflection effect and structural characteristics. In this paper, we prepare high-uniform silicon (Si) IPs structures on a commercial monocrystalline silicon wafer with a standard size of 156 × 156 mm2 employing the metal-assisted chemical etching (MACE) and alkali anisotropic etching technique. Combining the front IPs textures with the rear surface passivation of Al2O3/SiNx, we fabricate a novel Si IP-based passivated emitter and rear cell (PERC). Benefiting from the optical superiority of the optimized IPs and the improvement of electrical performance of the device, we achieve a high efficiency of 21.4% of the Si IP-based PERC, which is comparable with the average efficiency of the commercial PERC solar cells. The optimizing morphology of IP textures is the key to the improvement of the short circuit current Isc from 9.51 A to 9.63 A; meanwhile, simultaneous stack SiO2/SiNx passivation for the Si IP-based n+ emitter and stack Al2O3/SiNx passivation for rear surface guarantees a high open-circuit voltage Voc of 0.677 V. The achievement of this high-performance PV device demonstrates a competitive texturing technique and a promising prospect for the mass production of the Si IP-based PERC.

Copper-Ion-Assisted Precipitation Etching Method for the Luminescent Enhanced Assembling of Sulfur Quantum Dots.

In this study, we report a metal-ion-assisted precipitation etching strategy that can be used to manipulate the optical properties associated with the assembling of sulfur quantum dots (S dots) using copper ions. Transmission electron microscopy confirmed that the S dots were mainly distributed within 50-80 nm and that they exhibited an ambiguous boundary. After the post-synthetic Cu2+-assisted modification was completed, the assisted precipitation-etching S dots (APE-S dots) were observed to exhibit a relatively clear boundary with a high fluorescence (FL) quantum yield (QY) of 32.8%. Simultaneously, the Fourier transform infrared radiation, X-ray photoelectron spectra, and time-resolved FL decay spectra were used to illustrate the improvement in the FL QY of the APE-S dots.

Superior broadband antireflection from buried Mie resonator arrays for high-efficiency photovoltaics.

Establishing reliable and efficient antireflection structures is of crucial importance for realizing high-performance optoelectronic devices such as solar cells. In this study, we provide a design guideline for buried Mie resonator arrays, which is composed of silicon nanostructures atop a silicon substrate and buried by a dielectric film, to attain a superior antireflection effect over a broadband spectral range by gaining entirely new discoveries of their antireflection behaviors. We find that the buried Mie resonator arrays mainly play a role as a transparent antireflection structure and their antireflection effect is insensitive to the nanostructure height when higher than 150 nm, which are of prominent significance for photovoltaic applications in the reduction of photoexcited carrier recombination. We further optimally combine the buried Mie resonator arrays with micron-scale textures to maximize the utilization of photons, and thus have successfully achieved an independently certified efficiency of 18.47% for the nanostructured silicon solar cells on a large-size wafer (156 mm × 156 mm).

High-efficiency nanostructured silicon solar cells on a large scale realized through the suppression of recombination channels.

Nanostructured silicon solar cells show great potential for new-generation photovoltaics due to their ability to approach ideal light-trapping. However, the nanofeatured morphology that brings about the optical benefits also introduces new recombination channels, and severe deterioration in the electrical performance even outweighs the gain in optics in most attempts. This Research News article aims to review the recent progress in the suppression of carrier recombination in silicon nanostructures, with the emphasis on the optimization of surface morphology and controllable nanostructure height and emitter doping concentration, as well as application of dielectric passivation coatings, providing design rules to realize high-efficiency nanostructured silicon solar cells on a large scale.

Direct detection of methicillin-resistant Staphylococcus aureus in sputum specimens from patients with hospital-associated pneumonia using a novel multilocus PCR assay.

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of hospital-associated pneumonia (HAP). The rapid identification of MRSA would be beneficial for early diagnosis. The study aimed to evaluate a multilocus, fluorescence-based PCR assay based on the detection of mecA and nuc genes for identification of S. aureusin lower respiratory tract (LRT) specimens. Sensitivity and specificity of the PCR assay were analyzed. Clinical evaluation for the assay was performed using LRT specimens from patients with HAP, and the sensitivity, specificity, positive and negative predictive values (PPV and NPV) were evaluated in comparison with semi-quantitative culture methods. The result showed the assay provided positive identification of all MRSA reference strains with a limit of detection for MRSA of 4 × 103 CFU/mL. Compared with semi-quantitative culture, the sensitivity, specificity, PPV and NPV were 100%, 89.6%, 75.0%, and 100%, respectively. A positive correlation between MRSA bacterial colonies and PCR copy number was found. The specificity and PPV reached 96.6% and 89.7% respectively, if the PCR copy number reached a definite positive threshold of 5.96 × 105. It suggested that this novel multilocus, fluorescence-based PCR assay proved to be a fast, sensitive and specific tool for direct detection of MRSA from LRT specimens.

Dominance of CTX-M-type extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli isolated from patients with community-onset and hospital-onset infection in China.

OBJECTIVE: To investigate CTX-M genotypes among extended-spectrum ß-lactamase-producing Escherichia coli (ESBL-EC) isolated from patients with community-onset and hospital-onset infections in China, their clonality and the distribution of CTX-M variants in different specimens of community-onset and hospital-onset infections. METHODS: ESBL-EC isolates were collected from general hospitals from 2011 to 2012 in China. Broth microdilution method antimicrobial susceptibility testing of 16 antibiotics was performed. Clinical data from community-onset and hospital-onset infections due to ESBL-EC were analyzed. ESBL-encoding genes were amplified by PCR and sequenced, and multilocus sequence typing (MLST) was performed for a random selection of predominant CTX-M type strains identified. RESULTS: A total of 1,168 ESBL-EC isolates were obtained from various clinical specimens, 41.7% of which were responsible for causing community-onset infections. The presence of urinary calculi was higher in community-onset infections, whereas malignancy, cardiovascular and cerebrovascular diseases, dementia, chronic renal disease, diabetes mellitus and surgical treatment were found to have higher proportions in hospital-onset infections. There was no significant difference in trauma between community-onset and hospital-onset infections. 96.2% of the isolates were detected to harbor blaCTX-M genes. blaCTX-M-1 group and blaCTX-M-9 group were detected at 40.7% and 48.7% respectively, and both positive group accounted for 10.6%. blaCTX-M-55 (24.8%) and blaCTX-M-15 (18.2%) were the major genotypes in blaCTX-M-1 group while blaCTX-M-14 (46.8%) was predominant in blaCTX-M-9 group. A comparison of blaCTX-M distribution in different specimens between ESBL-EC causing community-onset and hospital-onset infection showed no significant difference. A total of 229 isolates were tested for MLST. ST131 (14%) was the predominant type. ST648, ST405 and ST1193 were also detected. CONCLUSIONS: Community-onset ESBL-EC has emerged as a common pathogen in China. CTX-M-14 is the most commonly encountered, CTX-M-55 and CTX-M-15 have spread rapidly. ST131 is the predominant clonal group, and the great diversity of CTX-M-producing isolates of E. coli has emerged in China.