Field Emission Characteristics of Conducting Polymer Films Conditioned by Electric Discharge

A pure conducting polymer （PANI-CSA） film conditioned by an electric discharge was tentatively utilized as an cathode for emitting electrons under electric fields. The emission of electrons was observed using a phosphor （ZnO：Zn） screen excited by electrons from the conditioned film. The film morphology was investigated using a scanning electron microscope and it was found that undulate whisker-like sites formed on the surface. The emission was presumably due to the undulate whisker-like sites. The field enhancement factor was estimated to be as high as 1150. The electron emitting process of the PANI-CSA film conditioned by electric discharge was also discussed.

High-Resolution Mass Spectroscopy for Revealing the Charge Storage Mechanism in Batteries: Oxamide Materials as an Example

The pursuit of high-performance electrode materials is highly desired to meet the demand of batteries with high energy and power density.However,a deep understanding of the charge storage mechanism is always challenging,which limits the development of advanced electrode materials.Herein,high-resolution mass spectroscopy(HR-MS)is employed to detect the evolution of organic electrode materials during the redox process and reveal the charge storage mechanism,by using small molecular oxamides as an example,which have ortho-carbonyls and are therefore potential electrochemical active materials for batteries.The HR-MS results adequately proved that the oxamides could reversibly store lithium ions in the voltage window of 1.5–3.8 V.Upon deeper reduction,the oxamides would decompose due to the cleavage of the C–N bonds in oxamide structures,which could be proved by the fragments detected by HR-MS,^(1)H NMR,and the generation of NH_(3)after the reduction of oxamide by Li.This work provides a strategy to deeply understand the charge storage mechanism of organic electrode materials and will stimulate the further development of characterization techniques to reveal the charge storage mechanism for developing high-performance electrode materials.

Synthesis of nonlinear optical fluorinated polyimide/inorganic composites for photonic devices

A nonlinear optical (NLO) active alkoxysilane chromophore (SGDR1) was synthesized. A fluorinated polyimide/SGDR1 composite was prepared to improve the poor temporal stability of second-order NLO effects of the reported poled sol-gel film. The poled composite film was characterized by FTIR, DSC, TGA and UV-Vis. The composite displays good hydrophobic properties, high glass transition temperature (266 ℃), and high decomposition temperature (433 ℃). The second harmonic coefficient d33 of the composite was measured to be 16.77 pm/V by using maker fringe technique. The new NLO composite exhibits 85 % of the original d33 over 720 h at 100 ℃ and possesses much better stability than the reported sol-gel film.

基于平面离散曲线序列的三维几何结构识别

提出了一种由分层离散曲线序列识别物体三维特征的方法，定义了一些能够表达平面曲线基本特性的特征，设计了用于识别物体三维结构的特征函数，基于这些特征函数，物体被分解为柱体、锥体和曲线体的组合，给出了一些具体应用实例。

Robust spectral reconstruction algorithm enables quantum dot spectrometers with subnanometer spectral accuracy

Since the concept of computational spectroscopy was introduced,numerous computational spectrometers have emerged.While most of the work focuses on materials,optical structures,and devices,little attention is paid to the reconstruction algorithm,thus resulting in a common issue:the effectiveness of spectral reconstruction is limited under high-level noise originating from the data acquisition process.Here,we fabricate a computational spectrometer based on a quantum dot(QD)filter array and propose what we believe is a novel algorithm,TKVA(algorithm with Tikhonov and total variation regularization,and the alternating direction method of multipliers),to suppress the impact of noise on spectral recovery.Surprisingly,the new TKVA algorithm gives rise to another advantage,i.e.,the spectral accuracy can be enhanced through interpolation of the precalibration data,providing a convenient solution for performance improvement.In addition,the accuracy of spectral recovery is also enhanced via the interpolation,highlighting its superiority in spectral reconstruction.As a result,the QD spectrometer using the TKVA algorithm shows supreme spectral recovery accuracy compared to the traditional algorithms for complex and broad spectra,a spectral accuracy as low as 0.1 nm,and a spectral resolution of 2 nm in the range of 400 to 800 nm.The new reconstruction algorithm can be applied in various computational spectrometers,facilitating the development of this kind of equipment.

Double-ended passivator enables dark-current-suppressed colloidal quantum dot photodiodes for CMOS-integrated infrared imagers

Lead sulfide(PbS)colloidal quantum dot(CQD)photodiodes integrated with silicon-based readout integrated circuits(ROICs)offer a promising solution for the next-generation short-wave infrared(SWIR)imaging technology.Despite their potential,large-size CQD photodiodes pose a challenge due to high dark currents resulting from surface states on nonpassivated(100)facets and trap states generated by CQD fusion.In this work,we present a novel approach to address this issue by introducing double-ended ligands that supplementally passivate(100)facets of halidecapped large-size CQDs,leading to suppressed bandtail states and reduced defect concentration.Our results demonstrate that the dark current density is highly suppressed by about an order of magnitude to 9.6 nA cm^(2) at -10 mV,which is among the lowest reported for PbS CQD photodiodes.Furthermore,the performance of the photodiodes is exemplary,yielding an external quantum efficiency of 50.8%(which corresponds to a responsivity of 0.532 A W^(-1))and a specific detectivity of 2.5×10^(12) Jones at 1300 nm.By integrating CQD photodiodes with CMOS ROICs,the CQD imager provides high-resolution(640×512)SWIR imaging for infrared penetration and material discrimination.

Stable PbS colloidal quantum dot inks enable blade‑coating infrared solar cells

Infrared solar cells are more efective than normal bandgap solar cells at reducing the spectral loss in the near-infrared region,thus also at broadening the absorption spectra and improving power conversion efciency.PbS colloidal quantum dots(QDs)with tunable bandgap are ideal infrared photovoltaic materials.However,QD solar cell production sufers from small-areabased spin-coating fabrication methods and unstable QD ink.Herein,the QD ink stability mechanism was fully investigated according to Lewis acid–base theory and colloid stability theory.We further studied a mixed solvent system using dimethylformamide and butylamine,compatible with the scalable manufacture of method-blade coating.Based on the ink system,100 cm2 of uniform and dense near-infrared PbS QDs(~0.96 eV)flm was successfully prepared by blade coating.The average efciencies of above absorber-based devices reached 11.14%under AM1.5G illumination,and the 800 nm-fltered efciency achieved 4.28%.Both were the top values among blade coating method based devices.The newly developed ink showed excellent stability,and the device performance based on the ink stored for 7 h was similar to that of fresh ink.The matched solvent system for stable PbS QD ink represents a crucial step toward large area blade coating photoelectric devices.

Heterogeneous system synthesis of high quality PbS quantum dots for efficient infrared solar cells

As promising optoelectronic materials,lead sulfide quantum dots(PbS QDs)have attracted great attention.However,their applications are substantially limited by the QD quality and/or complicated synthesis.Herein,a facile new synthesis is developed for highly monodisperse and halide passivated PbS QDs.The new synthesis is based on a heterogeneous system containing a PbCl_(2)-Pb(OA)_(2)solid-liquid precursor solution.The solid PbCl_(2)inhibits the diffusion of monomers and maintains a high oversaturation condition for the growth of PbS QDs,resulting in high monodispersities.In addition,the PbCl_(2)gives rise to halide passivation on the PbS QDs,showing excellent stability in air.The high monodispersity and good passivation endow these PbS QDs with outstanding optoelectronic properties,demonstrated by a 9.43%power conversion efficiency of PbS QD solar cells with a bandgap of~0.95 eV(1,300 nm).We believe that this heterogeneous strategy opens up a new avenue optimizing for the synthesis and applications of QDs.

Efficient quantum dot infrared solar cells with enhanced lowenergy photon conversion via optical engineering

Infrared(IR)solar cells are promising devices for improving the power conversion efficiency(PCE)of conventional solar cells by expanding the utilization region of the sunlight spectrum to near-infrared range.IR solar cells based on colloidal quantum dots(QDs)have attracted extensive attention due to the widely tunable absorption spectrum controlled by dot size and the unique solution processibility.However,the trade-off in QD solar cells between light absorption and photo-generated carrier collection has limited the further improvement of PCE.Here,we present high-performance PbS QD IR solar cells resulting from the combination of boosted light absorption and optimized carrier extraction.By constructing an optical resonance cavity,the light absorption is significantly enhanced in the range of 1,150–1,300 nm at a relatively thin photoactive layer.Meanwhile,the thin photoactive layer facilitates efficient carrier extraction.Consequently,the PbS QD IR solar cells exhibit a highly efficient photoelectric conversion in the IR region,resulting in a high IR PCE of 1.3%which is comparable to the highest value of solution-processed IR solar cells based on PbSe QDs.These results demonstrate that constructing an optical resonance cavity is a reasonable strategy for effective conversion of photons in the devices aiming at light in a relatively narrow wavelength range,such as IR solar cells and narrow band photodetectors.

用于PPG信号测试的大面积柔性胶体量子点红外光电二极管

以铟镓砷、碲镉汞等外延生长的单晶材料作为吸光层的光电二极管是红外探测技术的主流方案.然而,它们的刚性结构、极高成本以及有限尺寸使其无法满足诸如人体内外环境监测,便携式医疗等智能穿戴应用的需求.基于低温液相工艺的胶体量子点(CQDs)红外光电二极管是实现大面积柔性红外光电探测器极具竞争力的候选方案,但由于其发展年限较短,仍存在暗电流密度大、均匀性差以及工作稳定性差等问题.本文通过在CQDs墨水中引入聚酰亚胺来制备CQDs光电二极管.这种聚合物配体既实现了对CQDs表面缺陷态的钝化,又能够保持胶体墨水的单分散性和持久性.这两点使得光电探测器的吸光层形貌得以改善,同时暗电流密度显著降低,极大地优化了CQDs光电二极管的均匀性和工作稳定性.采用该方案制备的大面积柔性CQDs光电二极管能够实现高于10^(13)Jones的比探测率,可在环境光下实现可穿戴式光电体积描记(PPG)心率信号监测,极大地降低了成本和功耗.