Fluoro-substituted low band gap polymers based on isoindigo for air-stable polymer solar cells with high open circuit voltages

Two low band gap polymers (PIDT2FBT and PIDT4FBZ), which are composed of fluorinated elctron donor units (dithienyldifluorobenzothiadiazole (DT2FBT) and dithienyltetrafluorobenzene (DT4FBZ)) and a isoindigo electron accepting unit were implemented in a photoactive layer to invesitigate thier photovoltaic performance. Both low band gap polymers possess exhibit low-lying energy levels and extended light absorption range, which are essential to generate high open circuit voltage and short circuit current density of polymer solar cell. In addition, the blend with PC₇₁BM formed affirmative bulk heterojunction mrophology, resulting in promising power conversion efficiency up to 4.1% with high openc circuit voltage exceeding 1.1 V. Furthremore, the low-lying energy levels of the polymers leaded to good ambient stability of the devices up to 250 h, enabling PIDT2FBT and PIDT4FBZ to be promising candidates for photoactive layer of ambient stable polymer solar cells.     

Isoindigo-based polymer solar cells with high open circuit voltages up to 1.01 V

Isoindigo-based copolymers containing non-fluorinated (PIIDBT) and fluorinated bithiophene moieties (PIIDFBT) were synthesized. The replacement of hydrogen atoms with electronegative fluorine atom attained the intramolecular noncovalent interactions in conjugated polymer structure employing the concept of conformational locks. Furthermore, the fluorine characteristics as substituent atoms tuned the electron withdrawing ability and made the HOMO energy levels of fluorinated moieties deeper (−5.79 eV) than that of non-fluorinated polymer (−5.54 eV). As a result, the photovoltaic performance of PIIDFBT was improved by increasing its open circuit voltage (V_oc) up to 1.01 V, resulting in a power conversion efficiency of 6.21%. The PIIDFBT with high V_oc can be recognized as a promising candidate for both single junction and multi-junction photovoltaics.     

Properties of heterojunction based on pentacene and perylene derivatives

With the purpose of developing organic photosensitive cells with a wide photosensitivity spectrum and improved photogeneration characteristics, an ITO/pentacene/DiMe-PTCDI/Al heterostructure formed by alternate vacuum deposition of pentacene and perylene N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (DiMe-PTCDI) derivative films on the ITO substrate was studied. The effect of the heterostructure’s formation conditions on its spectral photosensitivity and photovoltaic properties was also studied. An analysis of current-voltage characteristics and frequency dependences of the impedance showed that the current through the heterojunction is controlled by thermionic emission with an ideality factor of 1.5–2.2, and the heterostructure can be simulated by an equivalent circuit consisting of two series elements representing the heterostructure bulk and space charge region.     

Application of copper thiocyanate for high open‐circuit voltages of CdTe solar cells

Copper thiocyanate (CuSCN) has proven to be a low‐cost, efficient hole‐transporting material for the emerging organic–inorganic perovskite solar cells. Herein, we report that CuSCN can also be applied to CdTe thin‐film solar cells to achieve high open‐circuit voltages (V_OCs). By optimizing the thickness of the thermally evaporated CuSCN films, CdTe cells fabricated by close space sublimation in the superstrate configuration have achieved V_OCs as high as 872 mV, which is about 20–25 mV higher than the highest V_OC for the reference cells using the standard Cu/Au back contacts. CuSCN is a wide bandgap p‐type conductor with a conduction band higher than that of CdTe, leading to a conduction band offset that reflects electrons in CdTe, partially explaining the improved V_OCs. However, due to the low conductivity of CuSCN, CdTe cells using CuSCN/Au back contacts exhibited slightly lower fill factors than the cells using Cu/Au back contacts. With optimized CdS:O window layers, the power conversion efficiency of the best CdTe cell, using CuSCN/Au back contact, is 14.7%: slightly lower than that of the best cell (15.2%) using Cu/Au back contact. Copyright © 2015 John Wiley & Sons, Ltd.     

Organic photovoltaic cells with vertically aligned crystalline molecular nanorods

We demonstrate the growth of vertically aligned nanorod arrays of copper phthalocyanine (CuPc) using the oblique angle deposition technique in high vacuum. High density nanorods with diameters down to 20 nm have been achieved with either stationary or rotational substrates. X-ray diffraction reveals the polycrystalline nature of the CuPc nanorods. Photovoltaic cells have been fabricated by spin-coating [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) onto the CuPc nanorod films to form the active region, and scanning electron micrographs show excellent infiltration of PCBM molecules into the gaps between the CuPc nanorods. A maximum power conversion efficiency of η_p = (1.8 ± 0.1)% under 1 sun AM 1.5G illumination has been achieved in a device with ～40 nm long CuPc nanorods deposited on a 20 nm thick flat CuPc film, approximately twice of that of optimized bilayer CuPc/PCBM devices.     

Schottky diodes with high breakdown voltages

The methods of increasing the breakdown voltages in silicon Schottky diodes is presented. In addition to a guarding ring, screen-diffusion regions were introduced. In this manner, the electrical field near the Schottky contact was lowered and, as a result, higher breakdown voltages were obtained. By using this method, the breakdown voltage can be increased by a factor of 3–5. However, a large device area is required for the same Schottky contact area and, therefore, the junction parasitic capacitance is greater.     

Organic photovoltaic cells based on self-assembly fabrication of vertically aligned CuPc nanorods upon fullerene particles

We demonstrate the self-assembled growth of vertically aligned Copper Phthalocyanine (CuPc) nanorods which are directly evaporated on fullerene (C₆₀) islands. UV–Vis spectroscopy of CuPc nanorods, compared to planar CuPc, shows an improvement in light absorption within the visible range. Moreover, scanning electron microscopy (SEM) demonstrates the presence of well-arranged vertically aligned CuPc nanorods suggesting an increase in the donor–acceptor interface. X-ray diffraction (XRD) reveals the crystalline nature of these nanorods. Different organic photovoltaic cells have been fabricated using these nanorods. High current density achieved with the cell arrangement of CuPc/CuPc-nanorods/C₆₀ in comparison to regular planar CuPc/C₆₀ device. The power conversion efficiency is also doubled compared to the planar one.     

Dual junction GaInP/GaAs solar cells grown on metamorphic SiGe/Si substrates with high open circuit voltage

Dual junction GaInP/GaAs solar cells have been grown and fabricated on Si substrates using relaxed, compositionally graded SiGe buffer layers that provide a nearly lattice-matched low threading dislocation Ge surface for subsequent cell growth. The dual junction cells on SiGe/Si displayed high open circuit voltages in excess of 2.2 V, compared to 2.34 V for control cells on GaAs, that are consistent with maintaining the 1.8/spl times/10/sup 6/ cm/sup -2/ threading dislocation density throughout the cell structure. Even with total current output limited by large grid coverage and high reflectance, total area AM1.5G efficiency is 16.8%, with active area efficiency at 18.6%. The high V/sub oc/ establishes that SiGe metamorphic buffers are viable for integrating III-V multijunction cells on Si in a monolithic process.     

High rectifier output voltages with printed organic charge pump circuit

It is known that in many wireless organic electronic applications the required supply voltage is higher than the accessible signal amplitude. Therefore, voltage multiplier circuits are needed in many cases. We report a gravure printed organic charge pump circuit operating at 13.56 MHz suitable for rectified voltage amplification in printed electronic devices. The circuit, consisting of four diodes and four capacitors, has been monolithically printed using only high volume production compatible manufacturing methods. With 10 V AC input the output of the circuit at 13.56 MHz is 8.4 V and 11.8 V using 1 MΩ and 10 MΩ output loads, respectively. At 13.56 MHz the output voltage of the charge pump is three times higher than the output of a half-wave rectifier. The results demonstrate the possibility to print efficient high frequency (HF) charge pump circuits to meet the supply voltage requirements of the printed electronic applications.     

Polymers from phenyl-substituted benzodithiophene and tetrafluoridequinoxaline with high open circuit voltage and high fill factor

A series of new copolymers from tetrafluoridequinoxaline (ffQx) and three distinctive phenyl (alkoxy-1-meta-fluorophenyl, alkoxyphenyl and alkylthiophenyl) substituted benzodithiophene (BDT), namely, PffQx-m-fPO, PffQx-PO and PffQx-PS, were designed and synthesized. Photophysical properties, charge mobilities and morphologies of the three polymers have been intensively investigated. Benefitted from the effects of phenyl and fluorine substituents on the backbone, all the polymers possess deep the highest occupied molecular orbital (HOMO) levels. In particular, PffQx-PS has a lower bimolecular recombination and deeper HOMO energy level, which contributes to the higher fill factor (FF, ca. 70%) and higher open-circuit voltage (V_oc, ca. 0.93 V) of the polymer solar cells (PSCs) with the polymer as donor and PC₇₁BM as acceptor. All the PSCs with the ffQx-based polymers as donor exhibited V_ocS higher than 0.9 V and power conversion efficiencies over 7% (7.0% for PffQx-m-fPO, 7.4% for PffQx-PO and 8.0% for PffQx-PS).     

基于光伏电池组件的ZigBee芯片供电电路设计

介绍了一种用于光伏电池组件的ZigBee芯片监控系统直接从光伏电池组件中获取电能、以保证ZigBee芯片监控系统正常工作的一种高效自适应供电电路设计。由于光伏电池组件输出电压在一天中变化较大,一般稳压电路模块不能承受这样的输入电压,同时因受安装空间和成本限制,一般DC/DC电路模块也不能选择。针对这样的情况,利用ZigBee芯片CC2430、RC延时电路、VMOS管调整电路、3.3 V稳压模块等通过巧妙设计,实现了在较大的直流电压波动环境下,高效稳定的输出3.3 V直流电压,为ZigBee芯片系统提供了稳定可靠的工作电能。     

Prototypes of photovoltaic cells based on subphthalocyanine with a lower buffer layer

Prototype organic photovoltaic cells containing a planar subphthalocyanine/fullerene heterojunction are fabricated. Their current-voltage characteristics are measured and basic photoconversion parameters are estimated. It was found that the morphology and conductive properties of the photoactive phthalocyanine layer depend on the presence and nature of the molecular sublayer on the anode surface onto which it is deposited. The use of indium chloride phthalocyanine as a sublayer increases the photoconversion efficiency in cells by a factor of 15.     

Non-destructive identification of open circuit in wiring on organic substrate with high wiring density covered with solder resist

As the printed wiring density on organic substrate is increasing, the line width and spacing are reducing toward 25 μm and below. Present method of fault isolation will no longer be adequate, and capacitive voltage contrast method is proposed. The feasibility of the voltage contrast method is demonstrated, and the various key parameters for better contrast are identified and determined. Circuit model is developed to explain the experimental results and the significance of the various key parameters.     

基于Cockcroft-Walton电路的PMT高压电源

根据当前实验室资源的需要合理分配与利用的需求,设计与实现了一种高效率、低纹波的PMT高压电源。该电源主要有LM10CLN电压控制部分,基于Cockcroft-Walton升压电路部分,反馈和保护电路部分和I-V转换部分来实现。最后完成电路的PCB板制作,通过对样品的试验,验证了本方案是可行的。电路运行良好,电路的线性度、纹波大小均符合要求。     

Increased photooxidation stability of pentacene derivatives linked with aromatic groups for OTFTs

Pentacene derivatives linked with aromatic groups at the 6,13-positions have been synthesized and characterized for their photooxidation properties. They exhibit high solubility which provides low-cost solution deposition methods. However, most of them are highly susceptible to photooxidation in solution determined with a few minutes of their half-life time under ambient conditions, practically precluding them from solution fabrication applications. Interestingly, their photooxidation stability can be significantly increased by blocking out light. The thin film transistor device for 3,4,5-trifluorophenyl-substituted pentacene (2c) showed the highest mobility of 1.1 × 10⁻² cm² V⁻¹ s⁻¹ with the threshold voltage of 20 V when it was prepared in the dark condition.     

基于无线收发信机的高频锁相环电路设计

在无线收发信机电路中,除了发射机和接收机外,还有一个非常重要的部分就是本地振荡电路.为了保证本地振荡模块输出信号的频率稳定性和较低的相位噪声,通常本振采用锁相环技术来实现,特别在无线通信领域.本文阐述了锁相环的基本结构和工作原理.     

p‐CuO/n‐Si heterojunction solar cells with high open circuit voltage and photocurrent through interfacial engineering

Heterojunction solar cells of p‐type cupric oxide (CuO) and n‐type silicon (Si), p‐CuO/n‐Si, have been fabricated using conventional sputter and rapid thermal annealing techniques. Photovoltaic properties with an open‐circuit voltage (V_oc) of 380 mV, short circuit current (J_sc) of 1.2 mA/cm², and a photocurrent of 2.9 mA/cm² were observed for the solar cell annealed at 300 °C for 1 min. When the annealing duration was increased, the photocurrent increased, but the V_oc was found to reduce because of the degradation of interface quality. An improvement in the V_oc resulting to a record value of 509 mV and J_sc of 4 mA/cm² with a high photocurrent of ~12 mA/cm² was achieved through interface engineering and controlling the phase transformation of CuO film. X‐ray diffraction, X‐ray photoelectron spectroscopy, and high‐resolution transmission electron microscopy analysis have been used to investigate the interface properties and crystal quality of sputter‐deposited CuO thin film. The improvement in V_oc is mainly due to the enhancement of crystal quality of CuO thin film and interface properties between p‐CuO and n‐Si substrate. The enhancement of photocurrent is found to be due to the reduction of carrier recombination rate as revealed by transient photovoltage spectroscopy analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

An alternative to supply DC voltages with high power factor

AC/DC is one of the most common power conversions in power electronics, DC loads should be fed with a stable and a tight regulated voltage. At the same time, the AC/DC converter should comply with low-frequency harmonic regulation. The classical two-stage AC/DC converters achieve these two objectives, although the overall efficiency is low because the power is processed twice. An alternative solution is presented in this paper. It is based on the division of the input power in two parts, one of them processed only once and keeping a unity power factor. This strategy improves the efficiency and reduces the size of the converter without any complex control scheme. This proposal can be implemented with a great variety of well-known topologies. The experimental results show that this solution is a good tradeoff between efficiency and size     

基于高速DSP的红外图像处理电路研究

介绍了一种基于高性能定点数字信号处理器(DSP)TMS320C6201的图像处理系统,该系统主要包括驱动电路模块、A／D和D／A转换模块、数字信号处理模块和视频显示模块。由于该系统采用了高性能、低功耗的处理芯片,使整个系统具有实时性高、性能稳定、精度高、体积小、功耗低等优点,在红外热成像系统中有着广泛的应用前景。     

Patchable thin-film strain gauges based on pentacene transistors

We present a patchable thin-film strain gauge for which output current responds sensitively to external strain. For this work, integrated organic thin-film transistors using pentacene as an active component were fabricated on a freestanding polyurethaneacrylate film with high flexibility and adhesive properties providing patchability. The device can be easily mounted onto non-flat surfaces, and the output characteristics show a strong correlation with the structural strain of freestanding polymeric film, which allows the external strain applied to the device to be gauged. In addition, a surface shape can be detected after mounting the device onto a non-flat surface, and the thickness of a complex structure can be inversely calculated using a calibration curve. It is anticipated that these results will be applied to the development of various patchable sensors and thickness measurement systems, which can lead to further applications.