Giant magneto field effect in up-conversion amplified spontaneous emission via spatially extended states in organic-inorganic hybrid perovskites

Up-conversion lasing actions are normally difficult to realize in light-emitting materials due to small multi-photon absorp-tion cross section and fast dephasing of excited states during multi-photon excitation.This paper reports an easily ac-cessible up-conversion amplified spontaneous emission(ASE)in organic-inorganic hybrid perovskites(MAPbBr3)films by optically exciting broad gap states with sub-bandgap laser excitation.The broad absorption was optimized by adjust-ing the grain sizes in the MAPbBr3 films.At low sub-bandgap pumping intensities,directly exciting the gap states leads to 2-photon,3-photon,and 4-photon up-conversion spontaneous emission,revealing a large optical cross section of multi-photon excitation occurring in such hybrid perovskite films.At moderate pumping intensity(1.19 mJ/cm2)of 700 nm laser excitation,a significant spectral narrowing phenomenon was observed with the full width at half maximum(FWHM)de-creasing from 18 nm to 4 nm at the peak wavelength of 550 nm,simultaneously with a nonlinear increase on spectral peak intensity,showing an up-conversion ASE realized at low threshold pumping fluence.More interestingly,the up-con-version ASE demonstrated a giant magnetic field effect,leading to a magneto-ASE reaching 120%.In contrast,the up-conversion photoluminescence(PL)showed a negligible magnetic field effect(<1%).This observation provides an evid-ence to indicate that the light-emitting states responsible for up-conversion ASE are essentially formed as spatially exten-ded states.The angular dependent spectrum results further verify the existence of spatially extended states which are polarized to develop coherent in-phase interaction.Clearly,using broad gap states with spatially extended light-emitting states presents a new approach to develop up-conversion ASE in organic-inorganic hybrid perovskites.

Hole Injection Enhancement of MoO3/NPB/Al Composite Anode

An ultra-thin molybdenum(VI)oxide(MoO3)modification layer can significantly improve hole injection from an electrode even though the MoO3 layer does not contact the electrode.We find that as the thickness of the organic layer between MoO3 and the electrode increases,the hole injection first increases and it then decreases.The optimum thickness of 5 nm corresponds to the best current improvement 70%,higher than that in the device where MoO3 directly contacts the Al electrode.According to the 4,4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl(NPB)/MoO3 interface charge transfer mechanism and the present experimental results,we propose a mechanism that mobile carriers generated at the interface and accumulated inside the device change the distribution of electric field inside the device,resulting in an increase of the probability of hole tunneling through the injection barrier from the electrode,which also explains the phenomenon of hole injection enhanced by MoO3/NPB/Al composite anode.Based on this mechanism,different organic materials other than NPB were applied to form the composite electrode with MoO3.Similar current enhancement effects are also observed.

高效蓝光钙钛矿发光二极管的埋底界面修饰和光耦合策略

Perovskite light-emitting diodes(PeLEDs)exhibit remarkable potential in the field of displays and solidstate lighting.However,blue PeLEDs,a key element for practical applications,still lag behind their green and red counterparts,due to a combination of strong nonradiative recombination losses and unoptimized device structures.In this report,we propose a buried interface modification strategy to address these challenges by focusing on the bottom-hole transport layer(HTL)of the PeLEDs.On the one hand,a multifunctional molecule,aminoacetic acid hydrochloride(AACl),is introduced to modify the HTL/perovskite interface to regulate the perovskite crystallization.Experimental investigations and theoretical calculations demonstrate that AACl can effectively reduce the nonradiative recombination losses in bulk perovskites by suppressing the growth of low-n perovskite phases and also the losses at the bottom interface by passivating interfacial defects.On the other hand,a self-assembly nanomesh structure is ingeniously developed within the HTLs.This nanomesh structure is meticulously crafted through the blending of poly-(9,9-dioctyl-fluorene-co-N-(4-butyl phenyl)diphenylamine)and poly(n-vinyl carbazole),significantly enhancing the light outcoupling efficiency in PeLEDs.As a result,our blue PeLEDs achieve remarkable external quantum efficiencies,20.4%at 487 nm and 12.5%at 470 nm,which are among the highest reported values.Our results offer valuable insights and effective methods for achieving high-performance blue PeLEDs.

一种新型抗SEU的SRAM单元结构设计

在加速器粒子物理实验中,基于专用集成电路(Application Specific Integrated Circuit,ASIC)在读出电子学前端实现模拟信号调理、数字化等功能是一个发展趋势,但这也使得ASIC暴露在了高能粒子辐射环境中,而其中的静态随机存储器(Static Random-Access Memory,SRAM)容易受到辐射的影响产生单粒子翻转(Single Event Upset,SEU),从而使芯片工作异常。因此对ASIC中的SRAM进行抗辐照加固设计十分必要。本工作提出了一种基于施密特触发器结构的11管抗SEU SRAM存储单元,并在180 nm CMOS工艺下进行了电路的设计和仿真,仿真结果表明,与传统12管SRAM单元相比,抗单粒子翻转能力有明显增加,且功耗仅为12管单元的42%。

Role of chloride on the instability of blue emitting mixed‑halide perovskites

Although perovskite light-emitting diodes(PeLEDs)have seen unprecedented development in device efciency over the past decade,they sufer signifcantly from poor operational stability.This is especially true for blue PeLEDs,whose operational lifetime remains orders of magnitude behind their green and red counterparts.Here,we systematically investigate this efciency-stability discrepancy in a series of green-to blue-emitting PeLEDs based on mixed Br/Cl-perovskites.We fnd that chloride incorporation,while having only a limited impact on efciency,detrimentally afects device stability even in small amounts.Device lifetime drops exponentially with increasing Cl-content,accompanied by an increased rate of change in electrical properties during operation.We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice due to an increased chemically and structurally disordered landscape with reduced migration barriers.Our results indicate that the stability enhancement for PeLEDs might require diferent strategies from those used for improving efciency.

罗霄山脉地区鱼类物种多样性

罗霄山脉是赣江和修水流域与湘江流域的分水岭,是中国生物多样性保护的关键地区之一。然而,罗霄山脉地区的鱼类缺乏系统性的研究,其鱼类物种组成、分布以及受威胁因素尚不清楚。为此,我们于2014–2018年对罗霄山脉地区11条河流的鱼类进行了系统的调查。结果表明,该地区共有鱼类5目17科64属113种,山脉东坡鱼类108种,高于西坡的72种。从生态类型看,罗霄山脉鱼类以肉食性、底栖性、定居性类群为主。区系组成上以东亚江河平原类群为主。从物种多样性看,遂川江、袁水、蜀水和修河的鱼类物种多样性较高,锦江和富水的鱼类物种多样性较低;β多样性指数揭示遂川江与锦江、禾水、富水间鱼类物种出现一定的分化现象。

Data-driven design of high-performance MASnxPb1-xI3 perovskite materials by machine learning and experimental realization

The photovoltaic performance of perovskite solar cell is determined by multiple interrelated factors,such as perovskite compositions,electronic properties of each transport layer and fabrication parameters,which makes it rather challenging for optimization of device performances and discovery of underlying mechanisms.Here,we propose and realize a novel machine learning approach based on forward-reverse framework to establish the relationship between key parameters and photovoltaic performance in high-profile MASnxPb1-xI3 perovskite materials.The proposed method establishes the asymmetrically bowing relationship between band gap and Sn composition,which is precisely verified by our experiments.Based on the analysis of structural evolution and SHAP library,the rapid-change region and low-bandgap plateau region for small and large Sn composition are explained,respectively.By establishing the models for photovoltaic parameters of working photovoltaic devices,the deviation of short-circuit current and open-circuit voltage with band gap in defective-zone and low-bandgap-plateau regions from Shockley-Queisser theory is captured by our models,and the former is due to the deep-level traps formed by crystallographic distortion and the latter is due to the enhanced susceptibility by increased Sn4+content.The more difficulty for hole extraction than electron is also concluded in the models and the prediction curve of power conversion efficiency is in a good agreement with Shockley-Queisser limit.With the help of search and optimization algorithms,an optimized Sn:Pb composition ratio near 0.6 is finally obtained for high-performance perovskite solar cells,then verified by our experiments.Our constructive method could also be applicable to other material optimization and efficient device development.