Charge carrier decay and diffusion in organic–inorganic CH3NH3PbI3–xClx perovskite based solar cell

In recent years, organic–inorganic lead halides attracted widespread interest, mainly due to their impressive photoconversion properties and low‐cost solution processing. In this study, we employed small amplitude transient photovoltage and photocurrent spectroscopy to investigate charge transport and recombination properties of perovskite CH₃NH₃PbI_3–xCl_x solar cell under realistic light harvesting conditions (<1 sun). Cell structure resembles outlay commonly found in organic photovoltaics, with perovskite absorber being sandwiched between two thin layers of organic polymers. Tested device displayed high power conversion efficiency (10.3%), good fill factor and negligible hysteresis effect. Fundamental device parameters were characterized at various open‐circuit voltages (V_oc) by examination of small voltage and current perturbations created by the low intensity pulsed laser excitations. The obtained results exhibit long charge carrier lifetimes and fast charge transport over the full range of applied optical bias, as well as remarkable diffusion lengths exceeding 1 μm. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Hot carrier degradation mechanism interpretation by lateral distribution of interface and bulk trap density

We investigated the drain avalanche hot carrier effect (DAHC) of p-type metal-oxide-semiconductor field effect transistor of 0.14 μm channel length (PMOSFET) with SiON gate dielectric. Using three different stress conditions of substrate maximum current, the changes to threshold voltage, maximum transconductance, saturation current and channel leakage current was monitored. Concurrently, the lateral distribution of interface trap density (N_it) and bulk trapped charge density (N_ot) with stress time has been extracted along the 70 nm half channels from gate edge to drain junction, which is the first endeavor in describing charge traps along sub 100 nm short channels. The degradation of the PMOSFET was described by combining electrical property with N_it and N_ot profiles. Hot electron punch through (HEIP) effect was evidenced by negative Not distribution near the drain junction while more severe hot carrier degradation was successfully demonstrated by the empirical power law dependence of the electrical parameters N_it and N_ot. We have studied the evolution of degradation behavior along highly scaled tens of nanometer channel, and N_it and N_ot profile offers systematic study and interpretation of degradation mechanism of hot carrier effect in MOSFET devices.     

Highly Efficient Deep-Red Non-Doped Diodes Based on a T-Shape Thermally Activated Delayed Fluorescence Emitter

Device simplification is of practical significance for organic light emitting diodes (OLEDs), and remains the great challenge for deep-red emitters. Herein, a deep-red thermally activated delayed fluorescence molecule ( p TPA-DPPZ ) is reported which features a T shaped structure containing two triphenylamine (TPA) donors, one either side of a planar dipyridophenazine (DPPZ) acceptor. The rational spatial arrangement of the functional groups leads to limited but sufficient molecular packing for effective carrier transport. The neat p TPA-DPPZ film achieves an around 90-fold improved radiation rate constant of 10⁷ s⁻¹ and the nearly unitary reverse intersystem crossing (RISC) efficiency, as well as accelerated emission decays for quenching suppression. The high radiation and RISC result in a photoluminescence quantum yield of 87 %. The bilayer OLED based on the p TPA-DPPZ emissive layer achieved the record external quantum efficiencies of 12.3 % for maximum and 10.4 % at 1000 nits, accompanied by the deep-red electroluminescence with the excellent color purity.     

Anisotropic charge carrier transport of optoelectronic functional selenium-containing organic semiconductor materials

Organic semiconductors (OSCs) materials are currently under intense investigation because of their potential applications such as organic field-effect transistors, organic photovoltaic devices, and organic light-emitting diodes. Inspired by the selenization strategy can promote anisotropic charge carrier migration, and selenium-containing compounds have been proved to be promising materials as OSCs both for hole and electron transfer. Herein, we now explore the anisotropic transport properties of the series of selenium-containing compounds. For the compound containing Se Se bond, the Se Se bond will break when attaching an electron, thus those compounds cannot act as n-type OSCs. About the different isomer compounds with conjugated structure, the charge transfer will be affected by the stacking of the conjugated structures. The analysis of chemical structure and charge transfer property indicates that Se-containing materials are promising high-performance OSCs and might be used as p-type, n-type, or ambipolar OSCs. Furthermore, the symmetry of the selenium-containing OSCs will affect the type of OSCs. In addition, there is no direct relationship between the R groups with their performance, whether it or not as p-type OSCs or n-types. This work demonstrates the relationship between the optoelectronic function and structure of selenium-containing OSCs materials and hence paves the way to design and improve optoelectronic function of OSCs materials.     

Separation of neutral and basic enantiomers by cyclodextrin electrokinetic chromatography using anionic cyclodextrin derivatives as chiral pseudo-stationary phases

Separations of neutral and basic racemates were performed using five different anionic cyclodextrin (CD) derivatives as chiral selectors, viz. carboxymethylated β-CD, β-CD phosphate sodium salt, sulfobutyl ether β-CD sodium salt, carboxymethylated γ-CD, and γ-CD phosphate sodium salt. For the separation of neutral racemates, an untreated fused silica capillary was employed and various neutral racemates were successfully separated. Since the pH of the buffer affected the electroosmotic flow (EOF), the resolution was improved by changing the buffer pH. A polyacrylamide coated capillary was employed for the separation of basic racemates to suppress EOF and to prevent adsorption of cationic analyte on the capillary surface. By choosing an appropriate type and concentration of anionic CD, about 40 basic racemates were successfully separated. Some rough binding constants of basic analytes with an anionic β-CD were measured to discuss the optimum concentration of the CD. The migration direction was dependent on the binding constants and the concentration of the CD. The analyte strongly bound to the anionic CD migrated towards the anode but the weakly bound one moved towards the cathode. Anionic γ-CDs were also very useful for the separation of basic enantiomers. Five neutral CDs were employed as chiral selectors to compare selectivity between charged and neutral CDs, and eleven racemates could only be resolved using anionic CDs. The separation of some basic racemates in human plasma was also described. The direct injection of plasma samples was possible for some enantiomers that did not interact strongly with plasma proteins.     

掺杂型红色有机电致发光显示器件

全色显示是有机电致发光显示(OLED)器件发展的目标,而高性能红色发光器件一直是制约全彩色OLED器件实用化的瓶颈,也是目前有机电致发光显示研究的热点。制作了掺杂DCJTB和不同浓度的rubrene两种荧光染料的红色有机电致发光显示器件,以NPB和Alq₃分别作为空穴传输层和电子传输层,发现器件性能与只掺杂DCJTB的器件相比有明显提高,发光效率提高到2～3倍。通过Frster理论和能带理论分析了器件的能量转移机理,研究发现Frster能量转移不是掺杂器件能量转移的主要形式,载流子俘获机制才是器件效率提高的主要原因;rubrene的引入使得能量能够更有效地从Alq₃转移到DCJTB,从而显著地提高了器件的发光效率和性能。     

中性红分光光度法测定肝素钠的研究

在pH 3.0的Britton-Robinson(B-R)缓冲溶液中,中性红与肝素钠相互作用形成复合物而导致溶液吸收光谱发生变化,用分光光度法对光谱变化进行了研究。 中性红溶液在523 nm处有一个强的特征吸收峰,当在其溶液中加入肝素钠后,溶液发生褪色现象,吸收峰强度降低,且没有新的吸收峰出现,吸光度差值(ΔA)与肝素钠的浓度成正比。 对结合反应的条件进行了优化,在最佳条件下利用溶液吸光度值的降低与肝素钠浓度的关系建立了一种测定肝素钠浓度的新方法,测定的线性范围为0.10～15.0 mg·L-1,表观摩尔吸光系数ε=2.037×106 L·mol-1·cm-1,检测限(3σ)为0.073 mg·L-1。 将该方法应用于肝素钠注射液效价的测定,结果令人满意。 用摩尔比法对复合物的结合比进行了推算,两者形成1∶3的复合物。     

溴吸附对碳纳米管导电性能的提高

通过溴蒸气的吸附, 提高多壁碳纳米管(MWNT)的本征导电性能,加溴多壁碳纳米管的电导率提高3倍. 通过拉曼光谱, 紫外可见光谱, 红外吸收光谱, 近红外吸收光谱和X光电子能谱等方法研究, 结果表明: 溴与多壁碳纳米管之间存在共轭作用, 使多壁碳纳米管表面的电子云分布发生了变化, 导致空穴载流子的产生, 增加了载流子浓度, 提高了多壁碳纳米管的导电性能.     

双安息香缩三乙四胺双核钴硫氰酸根的离子电极研究

季铵盐型阴离子选择性电极由于其电位选择性往往表现出Hofmeister顺序,故使其应用受到限制,因此,研究呈现反Hofmeister行为的阴离子选择性电极已成为离子电极研究领域中重要的研究方向之一。近年来,人们研制出了以金属配合物为中性载体且呈现反Hofmeister行为的阴离子选择电极,本实验室也分别研究了以Schiff碱金属配合物及二氮杂四烯基金属配合物为载体的碘离子和水杨酸根离子电极,但上述电极多数是以单核金属配合物为载体,以双核金属配合物作为载体的电极则很少。