355 nm激光作用下间甲苯酚的多光子电离质谱研究

利用355nm激光作为光源对间甲苯酚分子进行了多光子电离解离研究,得到了间甲苯酚分子的多光子电离飞行时间质谱图,实验中没有观测到母体离子信号。对其中的部分产物离子进行分析,得出了该波长下主要的解离电离通道。应用从头计算理论,在B3LYP/6-311++G(d,p)基组水平上对质荷比为109(C₇H₈OH⁺)离子及C₇H₈O的可能构型进行优化,得到了其稳定构型。对C₇H₈OH⁺离子势能面的研究得到,C₇H₈OH⁺离子的形成是一个无势垒的反应过程。     

Surface etching of 6H-SiC (0001) and surface morphology of the subsequently grown GaN via MOCVD

The correlation between surface morphological properties of the GaN epilayers and the surface conditions of 6H-SiC (0001) substrates etched in H₂, C₂H₄/H₂, and HCl/H₂ was studied. Etching 6H-SiC in H₂ produced a high quality surface with steps and terraces, while etching in HCl/H₂ produced either a rough surface with many pits and hillocks or a smooth surface similar to that etched in H₂, depending on the HCl concentration and temperature. The GaN epilayers were subsequently deposited on these etched substrates using either a low temperature GaN or a high temperature AlN buffer layer via MOCVD. The substrate surface defects increased the density and size of the “giant” pinholes (2–4 μm) on GaN epilayers grown on a LT-GaN buffer layer. Small pinholes (<100 nm) were frequently observed on the samples grown on a HT-AlN buffer layer, and their density decreased with the improved surface quality. The non-uniform GaN nucleation caused by substrate surface defects and the slow growth rate of planes of the islands were responsible for the formation of “giant” pinholes, while the small pinholes were believed to be caused by misfit dislocations.     

MP-CVD中CH4浓度对CH4/H2等离子体中基团的影响

采用发射光谱法(OES)诊断了微波等离子体化学气 相沉积(MP-CVD)制备金刚石膜过程中CH₄浓度对 CH₄/H₂等离子 体中基团分布的影响,并利用拉曼光谱对不同CH₄浓度下沉积的金刚石膜生长面进行表 征。研究表明:CH₄/H₂等离子体中存在Hα、Hβ、Hγ、CH、C₂基团,且各基团谱线强度随CH₄浓度 的增加而增强,其中C₂基团的光 谱强度显著增强;CH₄/H₂等离子体电子温度随CH₄浓度的增加而上升;光谱空间诊 断发 现等离子体球中基团 沿径向分布不均匀,随CH₄浓度增加,C₂和CH基团分布的均匀性显著变差;沉积速率 测试表明,单纯增加CH₄浓度不能有效提高金刚石膜的沉积速率;Raman光谱测试结果 表 明,低CH₄浓度(0.8%)下沉积出的金刚石膜质量更理想。     

WO3对Rubrene/C70有机太阳能电池性能的改善

研究了WO₃对Rubrene/C₇₀有机太阳能电池 (OSCs)性能的 改善,制备了结构为ITO/WO₃/Rubrene/C₇₀/BCP/Al的OSCs,其中WO₃插入在I TO和Rubrene中间作为阳极修饰层。通过优化WO₃的厚度,研究了WO₃对OSCs性能的改善及其作用机理。实验发现,器件的短路电流Jsc、开路电压V_oc、 填充因子(FF)、光电转换效率(PCE)和串联电阻Rs等性能参数随WO₃厚度的变化呈规律性变化;当 WO₃厚度小于80 nm时,器件PCE随着厚度的增加不断增大;当W O ₃厚大于80 nm时,器件PCE随着厚度的 增加不断减小;当WO₃厚度为80 nm 时,器件PCE达到最高为1.03%, 相应的J sc、V_oc、FF分别为2.81mA·cm－2、 0.83V、43.85%,Rs为45.3Ω·cm²,对比没有WO₃修饰层, 器件的J_sc、V_oc、FF和PCE分别提高了31%、137%、17%,Rs降低了33%。     

基于PIN结构的Rubrene/C70太阳能电池的性能研究

实验制备了ITO/V₂O₅/Rubrene/C₇₀:Rub rene/C₇₀/BCP/Al的PIN结构有机太阳能电池(OSC),其中 Rubrene、Rubrene:C₇₀和C₇₀分别作为P、I和N层。通过改变I层厚度,研究了I 层对OSC性能的影响及作用机理。实验显示,I层厚为5nm时器件的功率转换效率η达到最大值为1.580%,同时 获得了较大的短路电流密度Jsc为4.365mA· cm－2;相对PN结构器件,功率转化效率η短路电流密度Jsc和填充因子FF分别提 高了40.3%、29.7%和8.2%。我们认为,I层中激子分离效率的提高导 致了器件性能的改善。     

Chloride-based fast homoepitaxial growth of 4H-SiC films in a vertical hot-wall CVD

Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition (CVD) system using H₂-SiH₄-C₂H₄-HCl. The effect of the SiH₄/H₂ ratio and reactor pressure on the growth rate of 4H-SiC epilayers has been studied successively. The growth rate increase in proportion to the SiH₄/H₂ ratio and the influence mechanism of chlorine has been investigated. With the reactor pressure increasing from 40 to 100 Torr, the growth rate increased to 52 μm/h and then decreased to 47 μm/h, which is due to the joint effect of H₂ and HCl etching as well as the formation of Si clusters at higher reactor pressure. The surface root mean square (RMS) roughness keeps around 1 nm with the growth rate increasing to 49 μm/h. The scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) demonstrate that 96.7 μm thick 4H-SiC layers of good uniformity in thickness and doping with high crystal quality can be achieved. These results prove that chloride-based fast epitaxy is an advanced growth technique for 4H-SiC homoepitaxy.     

ZnO缓冲层改善Rubrene/C70有机太阳能电池的性能

通过制备结构为ITO/ZnO/C₇₀ /Rubrene/MoO₃/Al 的有机太阳能电池(OSCs),研究了ZnO作为阴极 修饰层对Rubrene/C70有机太阳能电池性能的改善。同时通过 优化ZnO的厚度研究了ZnO的工作机理。 从实验结果可以看出,随着ZnO厚度的变化,器件的短路电流密度(J_sc)、开路电压(V_oc)、填充因子 (FF)、光电转换效率(PCE)和串联电阻(R_s)等性能参数呈现出了规律 性变化,当ZnO层厚度比较 薄时,器件PCE随着厚度的增加不断增大,当ZnO层厚度为53nm时,器件PCE达到最高为1.13%, 对应的J_sc、V_oc、FF分别为2.82mA·cm－2、0. 84V、45.86%,R_s为66.2Ω·cm²,当ZnO层厚度继续增 加时,器件PCE开始减小。对比没有ZnO阴极修饰层,器件最优时 的Jsc、V_oc、FF和PCE 分别提高了49%、17%,R_s降低了56%。     

The investigation of an amidine-based additive in the perovskite films and solar cells

Here, we introduced acetamidine (C₂H₃N₂H₃, Aa)-based salt as an additive in the fabrication of perovskite (CH₃NH₃PbI₃) layer for perovskite solar cells. It was found that as an amidine-based salt, this additive successfully enhanced the crystallinity of CH₃NH₃PbI₃ and helped to form smooth and uniform films with comparable grain size and full coverage. Besides, perovskite film with additive showed a much longer carrier lifetime and an obviously enhanced open-circuit voltage in the corresponding devices, indicating that the acetamidine-based salt can reduce the carrier recombination in both the film and device. We further demonstrate a promising perovskite device based on acetamidine salt by using a configuration of ITO/TiO₂/Perovskite/Spiro-OMeTAD/Au under <150℃ fabrication condition. A power conversion efficiency (PCE) of 16.54% was achieved, which is much higher than the control device without acetamidine salt. These results present a simple method for film quality optimization of perovskite to further improve photovoltaic performances of perovskite solar cells, which may also benefit the exploration of A cation in perovskite materials.     

Detection of paramagnetic recombination centers in proton-irradiated silicon

The method of spin-dependent recombination was used to record electron spin resonance (ESR) spectra of recombination centers in a thin (∼1 μm) surface layer of p-type silicon grown by the Czochralski method and irradiated by protons with energies of ∼100 keV. Spectra of excited triplet states of the oxygen + vacancy complex (A-centers) were observed along with complexes consisting of two carbon atoms and an interstitial silicon atom (C_S-Si_I-C_S complexes). The intensity of the ESR spectra of these radiation-induced defects was found to be largest at irradiation doses of ∼10¹³ cm⁻², and decreased with increasing dose, which is probably attributable to passivation of the radiation-induced defects by hydrogen. Fiz. Tekh. Poluprovodn. 33, 1164–1167 (October 1999)     

Sr取代硬性PMS-PZT压电陶瓷研究

采用常规固相反应法合成了Pb_1-xSr_x(Mn_1/3Sb_2/3)_0.05Zr_0.48Ti_0.47O₃+0.25%CeO₂+0.50%Yb₂O₃+0.15%Fe₂O₃ (PMS-PZT, x=0, 0.02, 0.04, 0.06)的三元系硬性压电陶瓷。采用X线衍射仪、准静态压电常数测试仪和铁电测试仪系统地研究了Sr取代对PMS-PZT陶瓷的相结构及电学性能的影响。实验结果表明,无Sr取代和有Sr取代的PMS-PZT压电陶瓷均具有单一的四方相晶体结构。当x=0.02时,PMS-PZT的性能最佳:d₃₃=415 pC/N,Q_m=522,T_C=291 ℃,k_p=0.64,ε_r=1 304,Pr=11.32 μC/cm²,Ec=9.05 kV/cm。     

有机半导体器件的现状及发展趋势

从上世纪末和本世纪初开始,有机半导体材料研究引起了业界的广泛重视,使有机半导体器件的实验室制作水平得到大幅提高,并逐步进入当前的商品发展阶段。概述了有机半导体的发展历程、各种器件结构与特性及其技术现状;介绍了有机发光二极管(OLED)、太阳电池以及其他有机半导体器件的应用概况;探讨了有机半导体优于Si和GaAs等典型无机半导体技术的特点,分析讨论了有机半导体技术的发展前景;指出有机半导体器件有望成为解决传统半导体技术问题的有效途径。     

Interface Functionalities in Multilayer Stack Organic Light Emitting Transistors (OLETs)

Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field‐effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X‐ray diffraction and near edge X‐ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non‐ordered domains. Moreover, chemical reactivity at the interfaces is measured by X‐ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal‐organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties.     

基于6,13-二氯并五苯微纳米带的高性能有机光控晶体管

有机光控晶体管因其低成本、易加工等特点而受到广泛的关注。通过溶剂氛围滴膜法制备了基于6,13-二氯并五苯的微纳米带。采用氯苯做溶剂时,得到了形貌规则、晶形良好的微纳米带,而采用邻二氯苯做溶剂时,获得了大面积有序、定向生长的微纳米带。随后构筑了基于上述微纳结构的单根和多根微纳米带有机光控晶体管,器件显示了高的光敏特性。在很低强度的入射光(1.55mW/cm2)照射下,其光敏系数达1 300,表明6,13-二氯并五苯在有机微纳光控晶体管方面具有很好的应用前景。     

Redox‐Stability of Alkoxy‐BDT Copolymers and their Use for Organic Bioelectronic Devices

Organic semiconductors can be employed as the active layer in accumulation mode organic electrochemical transistors (OECTs), where redox stability in aqueous electrolytes is important for long‐term recordings of biological events. It is observed that alkoxy‐benzo[1,2‐b:4,5‐b′]dithiophene (BDT) copolymers can be extremely unstable when they are oxidized in aqueous solutions. The redox stability of these copolymers can be improved by molecular design of the copolymer where it is observed that the electron rich comonomer 3,3′‐dimethoxy‐2,2′‐bithiophene (MeOT2) lowers the oxidation potential and also stabilizes positive charges through delocalization and resonance effects. For copolymers where the comonomers do not have the same ability to stabilize positive charges, irreversible redox reactions are observed with the formation of quinone structures, being detrimental to performance of the materials in OECTs. Charge distribution along the copolymer from density functional theory calculations is seen to be an important factor in the stability of the charged copolymer. As a result of the stabilizing effect of the comonomer, a highly stable OECT performance is observed with transconductances in the mS range. The analysis of the decomposition pathway also raises questions about the general stability of the alkoxy‐BDT unit, which is heavily used in donor–acceptor copolymers in the field of photovoltaics.     

Highly Crystalline Rubrene Light-Emitting Diodes with Epitaxial Growth

Conventional organic optoelectronic devices suffer from low carrier mobility limited by the static and dynamic disorder. Organic crystals with long-range order can circumvent the effects of disorder and significantly improve the charge transport. While highly ordered organic crystals offer the desirable electronic coupling strength and charge transport, their integration into large-area optoelectronic devices remains a challenge. Here, monolithic integrated triclinic crystal rubrene light-emitting diodes (LEDs) are presented using epitaxial growth with functional additives being engineered into the films. Superior charge transport, excellent operational and long-term stability in these light-emitting devices are demonstrated. By comparing two rubrene-based LEDs, one made from amorphous and one from crystalline rubrene layers, their exciton dynamics are estimated using comprehensive transient electroluminescence simulation. The crystalline LEDs show high triplet-triplet annihilation (TTA) rate constant similar to TTA rate constant of triclinic single crystals determined by optical spectroscopy. At the same time, the crystalline phase enhances drastically the singlet-fission and bimolecular annihilation rates, which reduces the overall performance of the LED compared to its amorphous counterpart. Finally, an outlook on the potential applications of rubrene and/or its derivatives crystalline films are provided for enhancing the performance of organic and hybrid optoelectronic devices.     

Interface Engineering for Organic Electronics

The field of organic electronics has been developed vastly in the past two decades due to its promise for low cost, lightweight, mechanical flexibility, versatility of chemical design and synthesis, and ease of processing. The performance and lifetime of these devices, such as organic light‐emitting diodes (OLEDs), photovoltaics (OPVs), and field‐effect transistors (OFETs), are critically dependent on the properties of both active materials and their interfaces. Interfacial properties can be controlled ranging from simple wettability or adhesion between different materials to direct modifications of the electronic structure of the materials. In this Feature Article, the strategies of utilizing surfactant‐modified cathodes, hole‐transporting buffer layers, and self‐assembled monolayer (SAM)‐modified anodes are highlighted. In addition to enabling the production of high‐efficiency OLEDs, control of interfaces in both conventional and inverted polymer solar cells is shown to enhance their efficiency and stability; and the tailoring of source–drain electrode–semiconductor interfaces, dielectric–semiconductor interfaces, and ultrathin dielectrics is shown to allow for high‐performance OFETs.     

有机无线射频识别技术的研究进展

介绍了有机无线射频识别（RFID）标签的工作及制备技术原理。为了解决RFID标签的高成本一直制约RFID技术普及的问题,提出了采用有机半导体进行RFID标签制备的方案,分析了有机RFID标签的含义、构成、制备技术特点以及国外研究概况、未来市场状况等方面的内容。讨论了有机RFID与无机RFID标签在材料及加工工艺方面的区别,有机电子可以通过采用印刷工艺,完成大规模有机电路的集成,大大降低RFID标签的成本。指出有机RFID技术无论是生产材料还是生产方式都比无机RFID技术极具优势,符合未来商业化的要求及应用。     

The Multistep Tunneling Analogue of Conductivity Mismatch in Organic Spin Valves

Carbon‐based, molecular semiconductors offer several attractive attributes for spintronics, such as exceptionally weak spin‐orbit coupling and compatibility with bottom‐up nanofabrication. In spite of the promising properties of organic spin valves, however, the physical mechanisms governing spin‐polarized conduction remain poorly understood. An experimental study of C₆₀‐based spin valves is presented and their behavior is modeled with spin‐polarized tunneling via multiple intermediate states with a Gaussian energy distribution. It is shown that, analogous to conductivity mismatch in the diffusive regime, the magnetoresistance decreases with the number of intermediate tunnel steps, regardless of the value of the spin lifetime. This mechanism has been largely overlooked in previous studies of organic spin valves. In addition, using measurements of the temperature and bias dependence of the magnetoresistance, inhomogeneous magnetostatic fields resulting from interfacial roughness are identified as a source for spin relaxation and dephasing. These findings constitute a comprehensive understanding of the processes underlying spin‐polarized transport in these structures and shed new light on previous studies of organic spin valves.     

Naphthacenodithiophene Based Polymers—New Members of the Acenodithiophene Family Exhibiting High Mobility and Power Conversion Efficiency

Wide‐bandgap conjugated polymers with a linear naphthacenodithiophene (NDT) donor unit are herein reported along with their performance in both transistor and solar cell devices. The monomer is synthesized starting from 2,6‐dihydroxynaphthalene with a double Fries rearrangement as the key step. By copolymerization with 2,1,3‐benzothiadiazole (BT) via a palladium‐catalyzed Suzuki coupling reaction, NDT‐BT co‐polymers with high molecular weights and narrow polydispersities are afforded. These novel wide‐bandgap polymers are evaluated as the semiconducting polymer in both organic field effect transistor and organic photovoltaic applications. The synthesized polymers reveal an optical bandgap in the range of 1.8 eV with an electron affinity of 3.6 eV which provides sufficient energy offset for electron transfer to PC₇₀BM acceptors. In organic field effect transistors, the synthesized polymers demonstrate high hole mobilities of around 0.4 cm² V^–1 s^–1. By using a blend of NDT‐BT with PC₇₀BM as absorber layer in organic bulk heterojunction solar cells, power conversion efficiencies of 7.5% are obtained. This value is among the highest obtained for polymers with a wider bandgap (larger than 1.7 eV), making this polymer also interesting for application in tandem or multijunction solar cells.     

Very Low Degree of Energetic Disorder as the Origin of High Mobility in an n‐channel Polymer Semiconductor

Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings.