First-principles study on the electronic transport properties of M/SiC Schottky junctions (M=Ag,Au and Pd)

In this work, we investigate the electronic transport properties of M/SiC Schottky junctions (M=Ag, Au and Pd). The results show that the band structures of hydrogenated zigzag SiC nanoribbons (ZSiCNRs) and hydrogenated armchair SiC nanoribbons (ASiCNRs) are almost unaffected by their width changes. When the hydrogenated 7-ASiCNR is directly connected to the Ag, Au and Pd electrode, the transmission spectra of three metal-semiconductor junctions show that the Fermi level of metal is pinned to a fixed position in the semiconductor band gap of hydrogenated 7-ASiCNR. The nearly same rectifying current-voltage characteristics are found in three metal-semiconductor junctions. The average rectification ratios of three M/SiC Schottky junctions are all in the neighborhood of 10⁶. In other word, the M/SiC Schottky junction has remarkable application prospect as the candidate for Schottky Diode.     

基于器件结构提高TADF-OLED器件的发光性能

为了提高以TADF材料作为主体、天蓝色荧光材料作为客体的混合薄膜的OLED器件光电性能,我们调整了器件结构,使主体材料发挥其优势。制备了基本结构为ITO/NPB(40 nm)/DMAC-DPS∶x%BUBD-1(40 nm)/Bphen(30 nm)/LiF(0.5 nm)/Al的OLED器件。研究了主-客体材料在不同掺杂浓度下的OLED器件的光电特性。为了提高主体材料的利用率,在空穴传输层和发光层之间加入10 nm的DMAC-DPS作为间隔层;然后,在阳极和空穴传输层之间加入HAT-CN作为空穴注入层,形成HAT-CN/NPB结构的PN结,有效降低了器件的启亮电压(2.7 V)。测量了有无HAT-CN的单空穴器件的阻抗谱。结果表明,在最佳掺杂比例(2%)下,器件的外量子效率(EQE)达到4.92%,接近荧光OLED的EQE理论极限值;加入10 nm的DMAC-DPS作为间隔层,使得器件的EQE达到5.37%;HAT-CN/NPB结构的PN结有效地降低了器件的启亮电压(2.7 V),将OLED器件的EQE提高到5.76%;HAT-CN的加入提高了器件的空穴迁移率,降低了单空穴器件的阻抗。TADF材料作为主体材料在提高OLED器件的光电性能方面具有很大的潜力。     

Surface modulated hierarchical graphene film via sulfur and phosphorus dual-doping for high performance flexible supercapacitors

The steam-assistant heteroatoms of sulfur and phosphorus dual-doped graphene film fabricated via an ice-template and thermal-activation approach demonstrates an excellent pseudocapacitive behavior in flexible electrochemical capacitors.     

1200 V碳化硅功率MOSFET低温特性的实验表征及分析

碳化硅功率MOSFET是宽禁带功率半导体器件的典型代表,具有优异的电气性能。基于低温环境下的应用需求,研究了1200 V碳化硅功率MOSFET在77.7 K至300 K温区的静/动态特性,定性分析了温度对碳化硅功率MOSFET性能的影响。实验结果显示,温度从300 K降低至77.7 K时,阈值电压上升177.24%,漏-源极击穿电压降低32.99%,栅极泄漏电流降低82.51%,导通电阻升高1142.28%,零栅压漏电流降低89.84%(300 K至125 K)。双脉冲测试显示,开通时间增大8.59%,关断时间降低16.86%,开关损耗增加48%。分析发现,碳化硅功率MOSFET较高的界面态密度和较差的沟道迁移率,是导致其在低温下性能劣化的主要原因。     

Suppressing the environmental dependence of the open‐circuit voltage in inverted polymer solar cells through a radical polymer anodic modifier

Developing stable, readily‐synthesized, and solution‐processable transparent conducting polymers for interfacial modifying layers in organic photovoltaic (OPV) devices has become of great importance. Here, the radical polymer, poly(2,2,6,6‐tetramethylpiperidinyloxy methacrylate (PTMA), is shown to not affect the absorption of the well‐studied poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) active layer when incorporated into inverted OPV devices, as it is highly transparent in the visible spectrum due to the non‐conjugated nature of the PTMA backbone. The inclusion of this radical polymer as an anode‐modifying layer enhanced the open‐circuit voltage and short‐circuit current density values over devices that did not contain an anodic modifier. Importantly, devices fabricated with the PTMA interlayer had performance metrics that were time‐independent over the entire course of multiples days of testing after exposing the OPV devices to ambient conditions. Furthermore, these high performance values were independent of the metal used as the top electrode contact in the inverted OPV devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 311–316     

Freestanding Carbon Nanotube Film for Flexible Straplike Lithium/Sulfur Batteries

Flexible lithium/sulfur (Li/S) batteries are promising to meet the emerging power demand for flexible electronic devices. The key challenge for a flexible Li/S battery is to design a cathode with excellent electrochemical performance and mechanical flexibility. In this work, a flexible strap-like Li/S battery based on a S@carbon nanotube/Pt@carbon nanotube hybrid film cathode was designed. It delivers a specific capacity of 1145 mAh g⁻¹ at the first cycle and retains a specific capacity of 822 mAh g⁻¹ after 100 cycles. Moreover, the flexible Li/S battery retains stabile specific capacity and Coulombic efficiency even under severe bending conditions. As a demonstration of practical applications, an LED array is shown stably powered by the flexible Li/S battery under flattened and bent states. We also use the strap-like flexible Li/S battery as a real strap for a watch, which at the same time provides a reliable power supply to the watch.     

Dependence of electronic and optical properties of multilayer SiC and GeC on stacking sequence and external electric field

The electronic and optical properties of different stacked multilayer SiC and GeC are investigated with and without external electric field (EEF). The band gaps of multilayer SiC and GeC are found smaller than that of monolayer SiC and GeC due to the interlayer coupling effect. When EEF is applied, the direct band gaps (ΔK–M) of multilayer SiC and direct band gaps (ΔK–K) of multilayer GeC all turn to indirect band gaps (ΔK–G) as the band at the G point drops dramatically toward zero. The imaginary part ε₂(ω)s of multilayer SiC and GeC show that new absorption peaks between 2–5 eV appear when the polarized direction is perpendicular to the layer plane, and new absorption peaks in infrared region appear as the EEF is higher than a certain point when the polarized direction is parallel to the layer plane. Our calculations reveal that different stacking sequences and EEF can provide a wide tunable band structures and optical properties for multilayer SiC and GeC.     

Multichromophoric π‐Conjugation: Modular Design for Gated and Cascade Energy Transfer

Multichromophore arrays allow for cascade energy transfer. As an isoelectronic analogue of indacenyl, bis(triazolo)benzene features a fused tricyclic skeleton that rigidly places two π‐extended triazoles in close proximity. Such triazole‐based fluorophores behave as electronically independent modules in the ground states, but become tightly coupled upon photoexcitation for highly efficient excitation energy transfer (EET) that can be gated by external stimuli. Taking this donor–acceptor fluorophore system a step further, we have designed and implemented a cascade EET. Here, the initial excitation takes part in a circular relay to arrive at the longest‐wavelength emitting site as the final destination. Modularly constructed triazoloarenes should serve as versatile platforms for chemically controlled optical signaling.