有机半导体的物理掺杂理论

基于最低未被占据分子轨道（LUMO）和最高被占据分子轨道（HOMO）的高斯态密度分布与载流子在允许量子态中的费米-狄拉克（Fermi-Dirac）分布,提出有机半导体中物理掺杂的理论模型;研究了掺杂浓度、温度和禁带宽度对载流子浓度的影响,并与一些报道的实验结果做了比较.研究发现无论是否掺杂,温度升高时,有机半导体中的载流子浓度都会增大,并且随温度倒数的线性减小而指数增大;对于本征有机半导体,载流子浓度随禁带宽度的增大而指数下降,随高斯分布宽度的平方指数增加;对杂质和主体不同能级关系的掺杂情形下掺杂浓度对载 关键词： 有机半导体 掺杂 高斯态密度 载流子浓度     

Electronic properties close to Dirac cone in two-dimensional organic conductor α-(BEDT-TTF)<Subscript>2</Subscript>I<Subscript>3</Subscript>

A zero-gap state (ZGS) has been found in a bulk system of two-dimensional organic conductor, α-(BEDT-TTF)₂I₃ salt which consists of four sites of donor molecules in a unit cell. In the present paper, the characteristic of the ZGS is analyzed in detail and the electronic properties are examined in the vicinity of the Dirac point where the conduction and valence bands degenerate to form the zero-gap. The eigenvectors of the energy band have four components of respective sites, where two of them correspond to inequivalent sites and the other two correspond to equivalent sites. It is shown that the former exhibits an exotic momentum dependence around the contact point and the latter shows almost a constant dependence. The density of states of each site close to the Dirac point is calculated to demonstrate the temperature dependence of the local magnetic susceptibility and the local nuclear magnetic relaxation rate. Further, the robust property of the ZGS against the anion potential is also shown by using the second-order perturbation.     

Study of top and bottom contact resistance in one organic field-effect transistor

This paper reports that the organic field-effect transistors with hybrid contact geometry were fabricated, in which the top electrodes and the bottom electrodes were combined in parallel resistances within one transistor. With the facility of the novel structure, the difference of contact resistance between the top contact geometry and the bottom contact geometry was studied. The hybrid contact devices showed similar characteristics with the top contact configuration devices, which provide helpful evidence on the lower contact resistance of the top contact configuration device. The origin of the different contact resistance between the top contact device and the bottom contact device was discussed.     

Air stability of PTCDI‐C13‐based n‐OFETs on polymer interfacial layers

This Letter reports the novel use of poly(9‐vinylcarbazole) (PVK) as a dielectric interfacial layer for n‐type organic field‐effect transistors (n‐OFETs). With PVK, both the air stability and electron mobility of N,N′‐ditridecylperylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI‐C13)‐based OFETs were improved. Among the PVKs with different weight‐average molecular weight (M_w), PVK with high M_w showed good performance. The high glass transition temperature of PVK enabled thermal post annealing of the active layer, which resulted in a high electron mobility of 0.61 cm²/Vs. This mobility was maintained at 90% and 59% after 4 days and 105 days in air, respectively. The PVK interfacial layer reduced the trapped charges in the PTCDI‐C13‐based n‐OFET for air‐exposure and caused a decrease in the threshold voltage shift.

     

ULTRAHIGH DATA DENSITY STORAGE WITH SCANNING TUNNELING MICROSCOPY

Ultrahigh density data storage devices made by scanning probe techniques based on various recording media and their corresponding recording mechanisms, have attracted much attention recently, since they ensure a high data density in a non-volatile, erasable form in some kinds of ways. It is of particular interest to employ organic polymers with novel functional properties within a single molecule (or a single molecular complex) for fabricating electronic devices on a single molecular scale. Here, it is reported that a new process for ultrahigh density and erasable data storage, namely, molecular bistability on an organic charge transfer complex of 3-nitrobenzal malononitrile and 1,4-phenylenediamine (NBMN-pDA) switched by a scanning tunneling microscope (STM). Data density exceeds 10¹³ bits/cm² with a writing time per bit of ～1μs. Current-voltage (I/V) measurements before and after the voltage pulse from the STM tip, together with optical absorption spectroscopy and macroscopic four-probe I/V measurements demonstrate that the writing mechanism is conductance transition in the organic complex. This mechanism offers an attractive combination of ultrahigh data density coupled with high speed. The ultimate bit density achievable appears to be limited only by the size of the organic complex, which is less than 1nm in our case, corresponding to 10¹⁴ bits/cm². We believe that provided the lifetime can be improved, molecular bistability may represent a practical route for ultrahigh density data storage devices.     

基于蛋清栅绝缘层的高性能C_(60)有机场效应晶体管(英文)

采用生物材料(蛋清)作为栅绝缘层制备了基于C60为有源层的有机场效应晶体管。器件展现出了合理的电学特性,场效应迁移率和阈值电压分别为2.59 cm2·V-1·s-1和1.25 V。有机场效应晶体管展现良好性能的原因是蛋清具有较高的介电常数及热退火后形成的光滑表面形貌。实验结果表明,对于制备有机场效应晶体管来说,蛋清是一种有前途的绝缘层材料。     

Analysis of heterojunction resonant cavity-enhanced Schottky photodiodes by using two-valley transport model

The article concerns heterojunction resonant cavity-enhanced (RCE) Schottky photodiodes with GaAs in the absorption layer. The quantum efficiency and linear pulse response have thoroughly been analysed. For the first time, the response of a heterojunction photodiode has been modelled by the phenomenological model for a two-valley semiconductor. The results obtained have shown that the satellite valleys, as well as the parasitic time constant, significantly influence the response and, accordingly, have to be taken into account when analysing and optimizing RCE photodetectors.     

三维荧光指纹光谱用于污染河流溶解性有机物来源示踪研究

采用三维荧光指纹光谱技术对河流溶解性有机物荧光特征进行了研究。结果表明,污染河流中的溶解性有机物主要有腐殖质和蛋白质两类,类腐殖质荧光峰λ_激发/λ_发射为250/460 nm(A1),220/400 nm(A2)和325/420 nm(C);类蛋白质荧光峰λ_激发/λ_发射为285/357 nm(T1),230/360 nm(T2)。支流的类蛋白质荧光峰T1和T2由于生活污水的排放,其荧光强度都有明显增强。Fe3+离子在支流与干流汇合后浓度增加到支流的30倍,相应的类腐殖质荧光峰A1也发生了明显蓝移现象,而其他荧光峰则没有明显的偏移。激发波长较长的类腐殖质C,A1和类蛋白质T1荧光强度由于稀释及Fe3+等金属离子猝灭而明显降低,以至荧光峰消失。而较低激发波长的类蛋白质T2和UV类腐殖质A2荧光强度和荧光峰位置相对比较稳定,不容易受到溶液化学条件影响。激发波长220～230 nm荧光团可以用来示踪污染河流溶解性有机物。     

Degradation process in organic thin film devices fabricated using P3HT

The stability of regioregular poly(3-hexylthiophene 2,5-diyl) (P3HT) thin films sandwiched between indium tin oxide (ITO) and aluminium (Al) electrodes have been investigated under normal environmental conditions (25°C and RH∼45–50%). Electrical and optical properties of ITO/P3HT/Al devices have been studied over a period of 30 days. Mobility μ of the order of 10⁻⁴ cm²/V-s has been obtained from the V ² law in the as-deposited P3HT films. Scanning electron microscopy (SEM) investigations show blistering of Al contacts in devices with a poly(3,4-ethylenedioxythiophene) (PEDOT) interlayer on application of voltage whereas no blistering is seen in devices without PEDOT. The results have been explained in terms of trap generation and propagation and the moisture-absorbing nature of PEDOT.      

The structural and catalytic properties of nanoparticles@MOF composites: A case study of Au@ZIF-8 hybrid crystals

Strain analysis of the MOF and its composites using high-resolution X-ray diffractionmeter (XRD) was carried out and the presence of non-uniform, depth-related strain in the MOF crystals was confirmed. Further analysis showed that the magnitude and distribution of strain in MOF crystals can be tuned with the incorporation of nanoparticles (NPs). Moreover, the spatial controlled structures can also optimize functionalities of the NPs@MOF, which was exemplified by their applications on the catalytic reduction of nitroarenes. It is anticipated that the investigation of MOF structure evolution through controlling the architectures of the MOF/NPs hybrid materials will shed a light on the study of optimizing the mechanical and chemical properties of MOF composites.