Optical Properties of Neutral and Charged Low Band Gap Alternating Copolyfluorenes： TD-DFT Investigation

Electronic structure and optical properties of neutral and charged low band gap alternating copolyfluorenes （Green 1, which is based on alternating repeating units consisting of alkyl-substituted fluorene and a thiophene-[1,2,5]thiadiazolo-[3,4]quinoxaline-thiophene （T-TDQ-T） unit were investigated theoretically with time-dependent density functional theory （TD-DFT） method, and their excited state properties were further analyzed with 2D site and 3D cube representations. For neutral Green 1, the band gap, binding energy, exciton binding energy, and nuclear relaxation energy were obtained. The transition dipole moments of neutral and charged Green 1 are compared using 3D transition density, which reveals the orientation and strength of transition dipole moments. The charge redistribution of neutral and charged Green 1 upon excitation are displayed and compared with 3D charge difference density. The electron-hole coherences of neutral and charged Green 1 upon excitation are investigated with 2D site representation （transition density matrix）. The excited state properties of neutral Green 1 calculated with TD-DFT method are compared with that calculated with ZINDO method, which reveals the importance of electron-electron interaction （in TD-DFT） in the excited state properties.

Structural Tuning of Low Band Gap Intermolecular Push/Pull Side-chain Polymers for Organic Photovoltaic Applications

A series of novel low band gap donor-acceptor （D-A） type organic co-polymers （BT-F-TPA, BT-CZ-TPA and BT-SI-TPA） consisting of electron-deficient acceptor blocks both in main chains （M1） and at the pendant （M2） were polymerized with different electron rich donor （M3-M5） blocks, i.e., 9,9-dihexyl-9H-fluorene, N-alkyl-2,7-carbazole, and 2,6-dithinosilole, respectively, via Suzuki method. These polymers exhibited relatively low band gaps （1.65-1.88 eV） and broad absorption ranges （680-740 nm）. Bulk heterojunction （BHJ） solar cells incorporating these polymers as electron donors, blended with [6,6]-phenyl-C61-butyric acid methyl ester （PC61BM） or [6,6]-phenyl-Cvl-butyric acid methyl ester （PC71BM） as electron-acceptors in different weight ratios were fabricated and tested under 100 mW/cm2 of AM 1.5 with white-light illumination. The photovoltaic device containing donor BT-SI-TPA and acceptor PC71BM in 1：2 weight ratio showed the best power conversion efficiency （PCE） value of 1.88%, with open circuit voltage （Voc） = 0.75 V, short circuit current density （Jsc） = 7.60 mA/cm2, and fill factor （FF） = 33.0%.

Synthesis and properties of novel low band-gap polymers bearing squaraine units

Novel main-chain-conjugated poly(carbazol-alt-squaraine) and poly(dipyridyl-alt-squaraine) were successfully synthesized through direct polycondensation of 9-(2-ethylhexyl)carbazole-bridged or dipyridyl-bridged bispyrrole and squaric acid.The structures and properties of the polymers were characterized using ~1H NMR,FT-IR,UV-vis and cyclic voltammetry.Both polymers exhibit excellent solubility in common organic solvents and good thermal stability.Their UV-vis absorption spectra indicated the polymers have b...

Thienopyrazine or Dithiadiazatrindene Containing Low Band Gap Conjugated Polymers for Polymer Solar Cells

Four new low-band-gap alternating copolymers （P-1, P-2, P-3 and P-4） based on electron-rich benzodithiophene and newly developed electron-deficient units, thienopyrazine or dithiadiazatrindene derivatives, were synthesized by Stille polycondensation. All polymers exhibit good solubility in common organic solvents and a broad absorption band in the visible to near-infrared regions. The film optical band gaps of the polymers are in the range of 1.28-2.07 eV and the highest occupied molecular orbital （HOMO） energy levels are in the range of-4.99 eV to -5.28 eV. Bulk heterojunction polymer solar cells （PSCs） of the polymers were fabricated with phenyl-C61-butyric acid methyl ester （PC61BM） as acceptor material, and a power conversion efficiency of 0.80% was realized with P-1 as donor material.

Acceptor-Donor-Acceptor Type Small Molecular Low Band Gap Organic Semiconductors Containing 2-Dicyanomethylen- 3-cya n o-4, 5, 5-t rim ethyl-d i hyd rofu ran

Acceptor-donor-acceptor type compounds WI--W3 were designed and synthesized. These compounds had the same donor moiety of 2,6-di（tbiophen-2-yl）dithieno[3,2-b：2＇,3＇-d]thiophene and different acceptor groups of 2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran （TCF）, dicyanovinyl （DCV） and 3-ethyl-2-thioxothia- zolidin-4-one. Experimental results showed all compounds had high thermal stability and strong absorption in the visible light region. Among them, compound Wl with TCF as acceptor group displayed the lowest LUMO energy level of-3.74 eV and the smallest HOMO-LUMO band gap of 1.74 eV, suggesting the potential applications of TCF unit in low band gap organic semiconductors.

Synthesis and properties of copolymers based on 5,6-dinitrobenzothiadiazole with low band gap and broad absorption spectra

One polythiophene derivative PT3T and two low band gap copolymers,PBTT-T3T and PBTT,with different ratios of 5,6-dini-trobenzothiadiazole as the acceptor unit in the polymer backbone have been synthesized by Pd-catalyzed Stille-coupling polymerizations.Thermal stability,X-ray diffraction analyses,UV-vis absorption spectra,photoluminescence spectra and electrochemical properties of the copolymers were investigated.The band gap estimated from UV-vis-NIR spectra of the copolymers films varied from 1.39 to 1.94 eV.Among these copolymers,the films of PBTT-T3T and PBTT,which contain the 5,6-dinitrobenzothiadiazole unit,cover a broad wavelength range in the visible and near-infrared region from 400 to 1000 nm with the maximal peak absorption around 700 nm,which is exactly matched with the maximum in the photon flux of the sun.

Low Band Gap Polymers Synthesized by Electrochemical Polymerization for Electrochromic Devices

Two novel monomers, 10,13-bis（4-octyl-2-thienyl）-dibenzo[a,c]phenazine （OTBP） and 10,13-bis（4-octyl-2- thienyl）-dipyrido[3,2-a：2＇,3＇-c]phenazine （OTPP）, were synthesized. Electrochemical polymerization of OTPP and OTBP were carried out in acetonitrile/dichloromethane （ACN/DCM） solvent mixture containing tetra-n- butylammoniumhexafluorophosphate （TBAPF6）, and electrochromic properties of POTPP and POTBP are described. Furthermore, the effects of structural difference on electronic properties of electron acceptor units, electrochemical and electrochromic properties of two resulting polymers were examined. The results showed that the OTBP was polymerized at lower potential than OTPP, and this is because OTPP contains two more N atoms in electron acceptor unit and its electron withdrawing ability is stronger than that of OTBP. The UV-Vis-NIR spectra analysis revealed that the POTPP film has three absorption bands centered at 570 nm, 925 nm and 1581 nm, and the POTBP film has two absorptions at 566 nm and 1009 nm, respectively. The electrochromic properties indicated that the two polymer films exhibits reasonable optical contrasts and response time with low band gaps, defined as the onset of the absorption band at 570 nm for POTPP and the absorption band at 566 nm for POTBP, as 1.74 eV for POTPP and as 1.69 eV for POTBP.

Dithienopyrrole Based Small Molecule with Low Band Gap for Organic Solar Cells

A low band gap acceptor-donor-acceptor （A-D-A） small molecule donor material, named DR3TDTN, has been designed and synthesized for solution-processed organic solar cells. DR3TDTN shows narrow optical band gap with value of 1.49 eV and broad absorption spectrum from 300 to 820 rim. The HOMO and LUMO energy levels of DR3TDTN are -4.74 and -3.26 eV, respectively. The optimized photovoltaic device based on DR3TDTN：PC71BM blend film shows a power conversion efficiency of 3.03% with an open-circuit voltage of 0.67 V, a short-circuit current of 8.22 mA·cm^-2 and fill factor of 0.55.

基于声子晶体的高速列车地板支撑层隔声研究

随着高速列车运营速度不断提高,轨道交通产生的振动噪声会严重影响列车的车内声环境,进而降低乘坐舒适性,因此针对列车噪声源部位的车体隔声设计至关重要。目前的隔声措施能够有效控制车内中高频噪声,而对于低频噪声的抑制效果还有待进一步提升。声子晶体是一种具有弹性波带隙的周期性结构材料,该结构不需要大尺寸即可在局域共振作用下形成低频带隙,进而抑制弹性波的传播从而起到低频降噪作用。基于声子晶体周期性理论,以车辆转向架部位地板的木骨支撑层为对象,研究声子晶体在木骨支撑层隔声中的应用,系统分析声子晶体结构的带隙特性和隔声特性以及基于声子晶体结构的支撑层隔声性能。研究结果表明:通过改变结构形式及其参数可实现对于声子晶体结构的带隙形成频带及其隔声特性的人为设计和控制;以高速列车地板中的木骨结构为对象,结合声子晶体理论将其设计为木骨和声子晶体组合结构形式,不仅能够保持声子晶体在0~220 Hz低频段和620~710 Hz频段优越的隔声性能,同时可极大提升220~620 Hz频段的隔声性能;既维持该层结构的支撑作用,又能很好提升隔声性能,在高速列车地板设计中具有很强的有效性和适用性。

缝隙加载的低剖面双频北斗天线设计

本文设计了一款应用于北斗系统(BeiDou System,BDS)的新型低剖面双频段贴片天线.该天线基于单层贴片天线结构,通过“桥形”缝隙加载的方式,引入新的谐振频率,使天线工作在双频段(分别以1176 MHz和1575 MHz为中心频点),实现共面双频辐射.同时加载4个环形缝隙,仅用一组馈电针进行耦合馈电,方便调节阻抗匹配,同时减少馈电针数量,简化馈电网络复杂性.另外在天线侧面加载“π型”金属枝节,进一步优化高频阻抗匹配.实测结果表明,该天线在B1C频段和B2a频段的增益大于3.5 dBic,轴比均小于3 dB.频谱显示,该天线能工作于北斗系统的B1C、B2a频段,有望应用于北斗定位系统终端设备.

太赫兹功率放大单片封装技术研究

本文对太赫兹功率放大单片封装技术进行研究,主要包括波导-微带垂直过渡和模块内的模式谐振抑制技术.不同于常规的矩形探针平面过渡,本文提出了一种基于分叉探针的垂直过渡结构,适用于多层电路排布的系统/模块封装,并在WR-4波导频段(170~260 GHz)进行了背靠背结构的实验验证,在整个波导频带内,回波损耗优于16 dB,单个过渡的插入损耗约0.42 dB,这包括了波导模块接触不良造成的额外的损耗.为进一步降低过渡损耗,提出了一种开口谐振环结构,用来抑制不良接触导致的电磁泄漏,使过渡损耗降低为原来的一半.此外,为避免功率放大模块内部发生模式谐振,提出将电磁带隙结构设置在平面传输线的上腔来抑制高次模的激励、传输和谐振.应用上述技术对工作于210~230 GHz的功率放大单片进行封装及测试.在210 GHz,小信号增益达到最大值20.75 dB,单端封装损耗约0.8 dB;在217 GHz达到最大输出功率15.6 dBm,与芯片手册数据吻合较好.

A Novel BODIPY-Based Low-Band-Gap Small-Molecule Acceptor for Efficient Non-fullerene Polymer Solar Cells

We report herein an efficient A^1-C=C-A^2-C=C-A^1 type small-molecule 4,4＇-difluoro-4-bora-3a,4a-diaza-sindacene （BODIPY） acceptor （A^1= BODIPY and A^2= diketopyrrolopyrrole （DPP）） by following the A-to-A excited electron delocalization via the BODIPY meso-position, the inherent directionality for the excited electron delocalization. The lowest unoccupied molecular orbital （LUMO） delocalizes across over whole the two flanking A^1 and the central A^2, and the highest occupied molecular orbital （HOMO） localizes dominantly on the -C=C-DPP-C=C- segment. The excited electron upon light excitation of the DPP segment delocalizes over both the BODIPY and DPP segments. The acceptor in chloroform shows an unprecedented plateau-like broad absorption between 550 and 700 nm with a large FWHM value of 195 nm. Upon transition into solid film, the acceptor shows absorption in the whole near ultraviolet-visible-near infrared wavelength region （300-830 nm） with a low band gap of 1.5 eV and a maximum absorptivity of 0.85 × 10^5 cm^-1. Introduction of the ethynyl spacer between the A^1 and A^2 and the close BODIPY-to-DPP LUMO energy levels are crucial for the excited n-electron delocalization across over whole the conjugation backbone. A power conversion efficiency of 6.60% was obtained from the ternary non-fullerene solar cell with PTB7-Th：p-DTS（FBTTh2）2 （0.5 ; 0.5） as the donor materials, which is the highest value among the non-fullerene organic solar cells with BODIPY as the electron acceptor material.

Tetra-EDOT substituted 3D electrochromic polymers with lower band gaps

A couple of novel electrochromic materials poly(2,3,4,5-tetrakis(2,3-hydrothieno[3,4-b]dixin-5-yl)-1-methyl-1H-pyrrole)(P(t-EDOT-mPy))and poly(5,5',5",5'"-(thiophene-2,3,4,5-tetrayl)tetrakis(2,3-dihydrothieno[3,4-b][1,4]dioxine))(P(t-EDOTTh))are electrodeposited via multi-position polymerization of their tetra-EDOT substituted monomers t-EDOT-mPy and t-EDOT-Th,respectively.Compared with the linear 2D structured poly(thiophene)(E_g=2.2 eV)and poly(2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thiophene)(E_g=1.7eV),P(t-EDOT-Th)(E_g=1.62eV)has the lowest band gap.Hence,we speculate that the band gaps of the two polymers,having 3D structures,are decreased in contrast to non-substituted polymers or bi-EDOT substituted polymers,thiophene and 1-methyl-1H-pyrrole.The results indicated that P(t-EDOT-Th)thin films are more stable and show higher transmittance amid two polymers,which may find their utilization in organic optoelectronics.

Effect of Molecular Weight and Processing Additive on the Performance of Low Bandgap Polymer Solar Cells

In this work, we synthesized a low bandgap polymer polysilole（-2,6-diyl-alt-5-octylthieno[3,4-c]pyrrole-4,6- dione） （PDTSTPD） with different molecular weights （Mn）. The devices based on PDTSTPD/PC71BM composite are prepared and the dependence of power conversion efficiency （PCE） of the devices on the M,1 of conjugated poly- mers is addressed. We found the hole mobility of PDTSTPD is dependent on the Mn of the polymer, which should be the main reason contributing to the drastic difference of device performance, i.e. the PCE of the device using 10 kDa polymer is only 0.52%, in contrast to 2.3% for 24 kDa polymer device. This PCE data is then further improved to 5.0% via using 1,8-diiodoctane as processing additive to achieve an optimized morphology for the photoactive layer with an appropriate length-scale of phase separation for both exciton dissociation and charge transportation.

一种新型二维声子晶体的低频带隙特性及其形成机理

本文设计了一种新型的二维声子晶体结构,采用有限元法和等效模型法进行了深入研究,发现该结构具有良好的低频吸声性能。通过理论推导和仿真计算发现,在21 mm的晶格常数条件下,该结构在0~800 Hz具有完整的四条带隙。第一带隙下限低至40.28 Hz,且具有约为93 Hz的带宽,计算其传声损失后,发现其在低频域内具有良好的隔声效果,最大隔声量可达87.31 dB。对该结构的多个振动模态分析,建立相应的等效模型,并基于等效模型探究了不同因素对带隙频段造成的影响,总结出该新型二维声子晶体的一般性规律。研究结果表明,增大散射体密度和减小基体密度可以增加带宽,增大填充率和对散射体适当进行开孔处理可以改善带隙特性。该研究对于解决低频噪声控制问题具有一定参考意义和工程应用价值。

TID隔振器浮置板轨道低频减振特性研究

为了实现对地铁低频环境振动的控制,提出了一种基于TID(Tuned inerter damper,调谐惯容阻尼器)的浮置板板下隔振器,并以此形成新型浮置板轨道结构。分别探究了TID隔振器浮置板轨道的低频弹性波传播特性、简谐点荷载作用下振动特性以及列车荷载作用下减振效果;结合多目标遗传算法,开展了TID参数优化分析。结果表明:TID的引入使得传统钢弹簧浮置板新增弯曲波带隙,实现了对板内弹性波的调控;浮置板低频共振所致的振动放大问题得到较大改善。TID隔振器浮置板轨道在4 Hz~16 Hz频率范围内的减振效果得以提升,浮置板振动响应也得到减弱。

局域共振船体板架超结构低频隔振特性研究

声学超材料独特的亚波长带隙特性使其在船舶工业低频减振降噪领域呈现广泛的潜在应用价值。针对船舶机械设备低频振动和噪声控制问题,采用Solid-Shell多物理场耦合有限元法研究局域共振船体板架超结构弯曲波传播特性,分析船体板架超结构弯曲波带隙机理与减振特性,研究局域共振子的宽度与高度、面板厚度对弯曲波带隙特性与减振特性的影响。研究结果表明,相比典型船体板架结构及阻振质量船体板架结构,局域共振船体板架超结构在低频范围内存在弯曲波带隙,显示出优良的低频隔振性能,可以有效隔离船舶机械设备低频振动激励源。

基于间隙波导的毫米波宽带定向耦合器

本文基于新型间隙波导传输线技术,设计了一种宽带的0 dB前向波定向耦合器,提出的耦合器中心频率在30 GHz,可以实现宽带平坦的0 dB耦合特性,通过在两个相邻的槽间隙波导的公共壁上开耦合缝隙来实现主通道到副通道的能量耦合.为了方便实验测试,还设计了宽带的槽间隙波导到标准WR-28波导的过渡转换结构.最后进行了实物加工与测量,根据测量结果,本文提出的定向耦合器工作频带为27.1~31.5 GHz,带内最大插入损耗约为0.5 dB,且回波损耗小于-10 dB,耦合器的相对带宽为14.7%(中心频率30 GHz).测量结果与仿真结果吻合较好,实验验证了该设计方法的正确性.

一种多振子软基体声子晶体板的低频带隙特性研究

低频噪声与振动具有波长长、穿透能力强的特点,容易对人类的生产和生活造成严重影响。针对低频噪声控制,设计了一种椭圆铅球嵌在周期孔硅橡胶基体中的声子晶体板,利用有限元方法计算了其能带结构,并讨论了低频局域共振带隙形成机理。研究了散射体的填充率、高度、旋转角度以及材料参数和预应变对声子晶体板第一带隙宽度的影响。结果表明:所设计的声子晶体板能达到低频宽带隙的特点,施加在基体板上的预拉伸应变对其第一带隙影响较小。该研究为低频减振降噪结构设计和带隙优化提供了潜在理论参考价值。

二维局域共振周期格栅结构的低频振动带隙特性研究

为了解决周期格栅结构在低频领域的振动问题,基于局域共振机理,本文设计了一种新型复合二维周期格栅结构,结合有限元方法对结构的带隙机理及低频共振带隙特性进行了分析和研究,并在此基础上对结构进行优化设计。分析发现,仅对包覆层结构进行优化,便可大幅降低带隙的起始频率。带隙的位置由对应局域共振模态的固有频率决定,通过改变结构的材料和尺寸参数可以将带隙调节到满足实际工程应用的范围。数值仿真结果与试验测试结果一致,该结构可在40~90 Hz的低频范围打开宽度50 Hz的完全带隙,最大振动衰减达到36 dB。这种结构设计为周期格栅结构获得低频、超低频带隙提供了一种有效的方法,具有潜在的应用前景。