Charge carrier dynamics in different crystal phases of CH_(3)NH_(3)PbI_(3)perovskite

Despite that organic-inorganic lead halide perovskites have attracted enormous scientific attention for energy conversion applications over the recent years,the influence of temperature and the type of the employed hole transport layer(HTL)on the charge carrier dynamics and recombination processes in perovskite photovoltaic devices is still largely unexplored.In particular,significant knowledge is missing on how these crucial parameters for radiative and non-radiative recombinations,as well as for efficient charge extraction vary among different perovskite crystalline phases that are induced by temperature variation.Herein,we perform micro photoluminescence(pPL)and ultrafast time resolved transient absorption spectroscopy(TAS)in Glass/Perovskite and two dierent Glass/ITO/HTL/Perovskite configurations at temperatures below room temperature,in order to probe the charge carrier dynamics of different perovskite crystalline phases,while considering also the effect of the employed HTL polymer.Namely,CH_(3)NH_(3)Pbb films were deposited on Glass,PEDOT:PSS and PTAA polymers,and the developed Glass/CH_(3)NH_(3)PbI_(3)and Glass/ITO/HTL/CH_(3)NH_(3)PbI_(3)architectures were studied from 85 K up to 215 K in order to explore the charge extraction dynamics of the CH_(3)NH_(3)PbI_(3)orthorhombic and tetragonal crystalline phases.It is observed an unusual blueshift of the bandgap with temperature and the dual emission at temperature below of 100 K and also,that the charge carrier dynamics,as expressed by hole injection times and free carrier recombination rates,are strongly depended on the actual pervoskite crystal phase,as well as,from the selected hole transport material.

衬底对飞秒激光脉冲照射后薄金属目标光热响应的影响

飞秒脉冲激光器由于其在微、纳米尺度上图案制造精确的能力,在过去的几十年里得到了广泛的应用。对于高效材料加工,一个关键问题是确定在实验装置中使用的激光参数,而在已进行的系统研究中,主要是强调独立的单个参数的影响,很少关注辐照的固体基底材料的作用。因此,本研究强调了衬底对不同厚度薄膜的影响,结果表明,衬底的光学和热物理性质都对辐照薄膜上的热指纹有影响,在较小的薄膜尺寸下影响较大。选择了两种代表性材料硅和熔融硅作为不同光学和热物理形态薄膜(金和镍)的典型衬底,并对辐照的固体热响应和损伤阈值进行评估,为基于激光的制备装置和工艺的设计提供指导。

Ultrashort pulsed laser induced complex surface structures generated by tailoring the melt hydrodynamics

We present a novel approach for tailoring the laser induced surface topography upon femtosecond(fs)pulsed laser irradiation.The method employs spatially controlled double fs laser pulses to actively regulate the hydrodynamic microfluidic motion of the melted layer that gives rise to the structures formation.The pulse train used,in particular,consists of a previously unexplored spatiotemporal intensity combination including one pulse with Gaussian and another with periodically modulated intensity distribution created by Direct Laser Interference Patterning(DLIP).The interpulse delay is appropriately chosen to reveal the contribution of the microfluidic melt flow,while it is found that the sequence of the Gaussian and DLIP pulses remarkably influences the surface profile attained.Results also demonstrate that both the spatial intensity of the double pulse and the effective number of pulses per irradiation spot can further be modulated to control the formation of complex surface morphologies.The underlying physical processes behind the complex patterns’generation were interpreted in terms of a multiscale model combining electron excitation with melt hydrodynamics.We believe that this work can constitute a significant step forward towards producing laser induced surface structures on demand by tailoring the melt microfluidic phenomena.

金属原子诱导的微环境调控在聚合氮化碳光催化析氢中的研究

开发高效稳定的半导体光催化剂对光催化技术迈向实际应用至关重要.聚合物氮化碳(CN)因其优异的物理化学性质而被视为最具发展前景的制氢光催化剂之一.在过去几十年中,从热力学或动力学角度开发的一系列改性策略已经显著提升了CN的光催化制氢性能.近期,金属原子修饰策略为CN改性提供了一条新途径,这种策略可以精确调控CN的微环境.本文全面回顾了金属原子修饰的CN光催化剂在光催化分解水制氢领域的最新研究进展,包括金属单原子修饰的CN、金属双原子修饰的CN、金属单原子与团簇共修饰的CN,重点阐述了金属原子对提升光催化性能的关键作用.此外,本文还全面总结了发展先进的金属原子修饰的CN光催化剂所面临的挑战与机遇.

Post-glass melting synthesis and photochromic properties of composite AgCl-AgPO_(3)glasses

We herein present a simple,fast,low-temperature,post-glass melting fabrication protocol in which a photochromic silver cation based modified zone is incorporated within silver metaphosphate glass(AgPO_(3)).The selection of AgPO_(3)glass is mainly based on its relative“soft”nature(T_(g)=192℃)that enables the integration of silver cations from the surface deposited AgCl layer,while being transparent in most of the visible range,and therefore suitable for smart photochromic window applications.The suggested synthesis procedure permits the controlled formation of a silver cation modified layer within the host glass matrix,while the characteristics of the layer itself can be adjusted correspondingly.Our findings reveal a direct relationship between the developed composite AgCleAgPO_(3)glass photochromic response and the morphological features of the integrated layer,i.e.,thickness and position.More importantly,the photochromic response time with various UV irradiation doses is also studied,where remarkable response times of several seconds are obtained.Processes and efforts to further enhance the photochromic performance by utilizing the presence of silver nanoparticles within the glass matrix are also presented and discussed.

Morphology and Structure of Nb Thin Films Grown by Pulsed Laser Deposition at Different Substrate Temperatures

This paper reports the fabrication of Nb thin films through pulsed laser deposition at different substrate temperatures, ranging from 300 to 660 K. While the variation of the substrate temperature does not affect significantly the excellent Nb thin film adhesion to the Si（100） substrate surface, the increase of the substrate temperature up to 570 K promotes an improvement of the grown film in terms of morphology and roughness. Such improvement is achieved through the formation of wider columnar structures with a reduced superficial roughness, around 5 nm, as shown by scanning electron microscopy（SEM） and atomic force microscopy. The use of temperatures over 570 K increases the substrate roughness due to the formation of irregular structures inside the film, as observed by SEM cross section analysis, and does not produce a relevant improvement on the crystalline structure of the material.

Photocatalytic oxidation of gaseous benzene,toluene and xylene under UV and visible irradiation over Mn-doped TiO_(2)nanoparticles

The photocatalytic oxidation of gaseous benzene,toluene and xylene(BTX)over un-doped,0.1 and 1 wt%Mn-TiO_(2)nanoparticles under ultraviolet and visible irradiation was studied in atmosphere of synthetic air or inert gas.The photocatalytic decomposition efficiency and the oxidation products were determined using a Static Photochemical Reactor coupled with FTIR spectroscopy.BTX underwent efficient decomposition over Mn-TiO_(2)photocatalysts under UV irradiation,more with oxygen presence and less without oxygen.More important toluene and xylene went substantial decomposition over 0.1 mol%Mn-TiO_(2)under visible irradiation with oxygen presence.The main final oxidation products in the UV photocatalysis of BTX were CO_(2),CO and H2O,with CO_(2) and CO yields 4 and 2 respectively.The conversion percentage of benzene,toluene,and xylene to CO_(2) were 63.6%,56.4%,51.8%,and to CO 29%,26.5%,23.2%,respectively.In the visible photocatalysis of toluene and xylene the yields of CO were insignificant.Formation of carbon containing deposits on TiO_(2)surfaces was observed after extensive UV photocatalysis of toluene and xylene,and such by-products surface coverage may reduce the photocatalytic activity of TiO_(2)samples.Some aspects of the photocatalytic mechanism were examined.

Powerful terahertz waves from long-wavelength infrared laser filaments

Strong terahertz(THz)electric and magnetic transients open up new horizons in science and applications.We review the most promising way of achieving sub-cycle THz pulses with extreme field strengths.During the nonlinear propagation of two-color mid-infrared and far-infrared ultrashort laser pulses,long,and thick plasma strings are produced,where strong photocurrents result in intense THz transients.The corresponding THz electric and magnetic field strengths can potentially reach the gigavolt per centimeter and kilotesla levels,respectively.The intensities of these THz fields enable extreme nonlinear optics and relativistic physics.We offer a comprehensive review,starting from the microscopic physical processes of light-matter interactions with mid-infrared and far-infrared ultrashort laser pulses,the theoretical and numerical advances in the nonlinear propagation of these laser fields,and the most important experimental demonstrations to date.

Highly sensitive ozone and hydrogen sensors based on perovskite microcrystals directly grown on electrodes

Highly-sensitive and stable ozone and hydrogen sensing elements were fabricated based on well-crystalline rounded cube-shaped CsPbBr 3 microcrystals,synthesized by a facile solution process per-formed under ambient conditions.It is shown that such elements demonstrate enhanced room tem-perature gas sensing ability compared to the previously reported metal halide and oxide-based ones.Electrical measurements performed on these sensing components revealed high sensitivity to ultra-low ozone and hydrogen concentrations,namely 4 ppb and 1 ppm respectively,as well as a remarkable repeatability,even after a few months of storage in ambient conditions.Both ozone and hydrogen sensors were self-activated,as they did not require the use of UV or heating external stimuli to operate,and exhibited fast detection and short restoration times.All such attractive properties along with the simple fabrication process could provide an easy,efficient and low-cost technology for the realization of future gas sensing devices.

Observatory science with eXTP

In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.