Advances in composition control for 16 µm LPE P-on-n HgCdTe heterojunction photodiodes for remote sensing applications at 60K

With good composition control in both p-type cap and n-type base LPE layers, it is possible to make barrier-free two-layer P-on-n HgCdTe heterojunction photodiodes with very long cutoff wavelengths. Diode arrays with good R_oA operability, good quantum efficiency, and low 1/f noise at 60K have been demonstrated at cutoff wavelengths to 16.3μm. The diode performance continues to improve at lower temperatures, following a diffusion-current trend to at least 35K. Measured R_oA values of 2×10⁵ ohm-cm² for an 18 μm cutoff at 35K are the highest reported at this very long wavelength. A simple defect model applied to the area dependence of R_oA at 40K implied a defect areal density of 3×10⁴ cm⁻² and a defect impedance of 3×10⁶ ohm.     

基于双并联Boost电路的光伏系统最大功率点跟踪控制方法

光伏电池的输出功率取决于外界环境（温度和光照条件）和负载状况,需采用最大功率点跟踪（MPPT）电路,才能使光伏电池始终输出最大功率,从而充分发挥光伏器件的光电转换效能.在比较了常用光伏发电系统控制的优缺点后,依据MPPT控制算法的基本工作原理,主电路采用双并联Boost电路,具有电压提升功能,并且能够提高DC-DC环节的额定功率和减小直流母线电压的纹波.针对传统扰动观察法存在的振荡和误判问题,提出了一种新型的基于双并联Boost电路的改进扰动观察法最大功率跟踪策略.在Matlab/Simulink下进行了建模与仿真,仿真结果表明,当外界环境发生变化时,系统能快速准确跟踪此变化,避免算法误判现象的发生,通过改变当前的负载阻抗,使之与光伏电池的输出阻抗等值相匹配采满足最大功率输出的要求,使系统始终工作在最大功率点处,并且在最大功率点处具有很好的稳态性能.最后通过实验验证了该算法的有效性.     

Cyclopentadithiophene–benzothiadiazole oligomers: Synthesis via direct arylation,X-ray crystallography,optical properties,solution casted field-effect transistor and photovoltaic characteristics

This article reports the synthesis, crystallographic structure and OFET and OPV performance of the conjugated oligomer of cyclopentadithiophene (CPDT) with benzothiadiazole (BT). Synthesis of the oligomer composed of the CPDT-BT-CPDT sequence is accomplished using direct arylation reactions. Theoretical and experimental X-ray single crystallography confirms that two CPDT-BT-CPDT molecules are not entirely disordered, but are actually stacking directly across each other at the central BT units with an intermolecular distance of 3.61 Å, providing valuable insight into the polymer bulk structure. The performance of the oligomer in OFET devices is investigated by fabricating bottom gate top contact devices and demonstrates a hole mobility of 5.0 × 10⁻³ cm² V⁻¹ s⁻¹. OPV devices of the oligomer blended with PC₆₁BM and PC₇₁BM show power conversion efficiency (PCE) of 1.61%. One potential use for the oligomer could be as a sensitiser in a ternary blend with P3HT–PC₆₁BM or PCPDTBT–PC₆₁BM OPVs; the PCE can be relatively increased by 3–9% depending on concentration, primarily as a result of increased short circuit current density.     

Improved Performance of Molecular Bulk‐Heterojunction Photovoltaic Cells through Predictable Selection of Solvent Additives

Solvent additives provide an effective means to alter the morphology and thereby improve the performance of organic bulk‐heterojunction photovoltaics, although guidelines for selecting an appropriate solvent additive remain relatively unclear. Here, a family of solvent additives spanning a wide range of Hansen solubility parameters is applied to a molecular bulk‐heterojunction system consisting of an isoindigo and thiophene containing oligomer as the electron donor and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as the electron acceptor. Hansen solubility parameters are calculated using the group contribution method and compared with the measured solubilities for use as a screening method in solvent additive selection. The additives are shown to alter the morphologies in a semipredictable manner, with the poorer solvents generally resulting in decreased domain sizes, increased hole mobilities, and improved photovoltaic performance. The additives with larger hydrogen bonding parameters, namely triethylene glycol (TEG) and N‐methyl‐2‐pyrrolidone (NMP), are demonstrated to increase the open circuit voltage by ~0.2 V. Combining a solvent additive observed to increase short circuit current, poly(dimethylsiloxane), with TEG results in an increase in power conversion efficiency from 1.4 to 3.3%.     

Enhancement of the power conversion efficiency due to the plasmonic resonant effect of Au nanoparticles in ZnO nanoripples

Au-ZnO nanoripples (NRs) were synthesized by using a sol-gel method for utilization as an electron transport layer (ETL) in inverted organic photovoltaic (OPV) cells. Absorption spectra showed that the plasmonic broadband light absorption of the ZnO NRs was increased due to the embedded Au nanoparticles (NPs). In particular, as compared to regular inverted OPV cells with a ZnO NR ETL, the incident photon-to-current efficiency of the inverted OPV cells with a Au-ZnO NR ETL was significantly enhanced due to the localized surface plasmon resonance (LSPR) effect of the Au NRs. The enhancement of the short-circuit current density (10.05 mA/cm²) of the inverted OPV cells with a Au-ZnO NR ETL was achieved by the insertion of the Au NPs into the ZnO NRs. The power conversion efficiency (PCE) of the OPV cells with Au-ZnO NRs was 3.25%. The PCE of the inverted OPV cells fabricated with a Au-ZnO NR ETL was significantly improved by 20.37% in comparison with that of inverted OPV cells fabricated with a ZnO NR ETL. This improvement can mainly be attributed to an increase in light absorption in the active layer due to the generation of the LSPR effect resulting from the existence of the Au NPs embedded in the ZnO NRs.     

Global maximum power point tracking based on new extremum seeking control scheme

A new perturbed‐based extremum seeking control (PESC) scheme is proposed in this paper to track the global maximum power point (GMPP). The PESC scheme has two control loops based on power of the photovoltaic (PV) array: the first loop operates as usually to track the maximum power point and the second sweeps all local MPPs to locate the GMPP. Once the GMPP is located based on its uniqueness (after the PV pattern is quickly scanned many times, depending on the PV pattern's profile), the GMPP is accurately tracked based on first control loop. The used PV patterns have the profile of the PV power characteristics obtained for PV array under partially shaded conditions (PSCs). This PESC scheme is proposed to track the GMPP in the PV applications, but also in other multimodal problems from industry, being a good motif to revive the specialists' interest for the extremum seeking control field. The results obtained here are very promising for both search speed and tracking accuracy performances of the GMPP under different PSCs simulated on the PV array. Thus, the energy efficiency of PV array controlled with the proposed PESC scheme will increase with more than 1.2% in comparison with that obtained with the other MPP algorithms because of better performance shown by this PESC scheme. A 99.6% tracking accuracy is obtained here in comparison with a maximum 98.4% tracking accuracy reported in the literature. Furthermore, 100% hit and high search speed are obtained here for the GMPP localization. Copyright © 2015 John Wiley & Sons, Ltd.     

化合物半导体光伏产品发展趋势探讨

目前世界上能源消耗以化石燃料为主。化石燃料消耗所带来的能源供应危机以及环境污染,使人类社会的可持续发展承受着越来越重的压力,因此,新能源的推广应用已成为全球共识。太阳能有可能成为满足未来能源需求的战略性能源。其中化合物半导体光伏产品是未来地面太阳能应用的重要发展方向,而铜铟镓硒（CIGS）体系由于其本身的优点,是新一代化合物半导体光伏产品的重要发展方向。该体系在产业化技术方面已经取得很大的进展,并已逐步开始大规模产业化实践。     

Chiral Excitonic Organic Photodiodes for Direct Detection of Circular Polarized Light

A facile route to soft matter self‐powered bulk heterojunction photodiode detectors sensitive to the circular polarization state of light is shown based on the intrinsic excitonic circular dichroism of the photoactive layer blend. As light detecting materials, enantiopure semiconducting small molecular squaraine derivates of opposite handedness are employed. Via Mueller matrix ellipsometry, the circular dichroism is proven to be of H‐type excitonic nature and not originating from mesoscopic structural ordering. Within the green spectral range, the photodiodes convert circular polarized light into a handedness‐dependent photocurrent with a maximum dissymmetry factor of ±0.1 corresponding to 5% overall efficiency for the polarization discrimination under short circuit conditions. On the basis of transfer matrix optical simulations, it is rationalized that the optical dissymmetry fully translates into a photocurrent dissymmetry for ease of device design. Thereby, the photodiode's ability to efficiently distinguish between left and right circularly polarized light without the use of external optical elements and voltage bias is demonstrated. This allows a straightforward and sustainable future design of flexible, lightweight, and compact integrated platforms for chiroptical imaging and sensing.     

Recent Progress in Flexible and Stretchable Organic Solar Cells

Flexible and stretchable organic solar cells (OSCs) have attracted enormous attention due to their potential applications in wearable and portable devices. To achieve flexibility and stretchability, many efforts have been made with regard to mechanically robust electrodes, interface layers, and photoactive semiconductors. This has greatly improved the performance of the devices. State‐of‐the‐art flexible and stretchable OSCs have achieved a power conversion efficiency of 15.21% (16.55% for tandem flexible devices) and 13%, respectively. Here, the recent progress of flexible and stretchable OSCs in terms of their components and processing methods are summarized and discussed. The future challenges and perspectives for flexible and stretchable OSCs are also presented.     

BP神经网络在光伏发电系统故障诊断中的应用

介绍了并网光伏发电系统的故障诊断模式和故障原因,以及BP神经网络的结构与学习算法。针对太阳能并网光伏发电系统工作过程中可能出现的故障,提出了一种基于BP神经网络的故障诊断方法。测试结果表明了该方法的有效性和可能性,达到了预期的结果,可以用于并网光伏发电系统的故障诊断。